1 00:00:00,090 --> 00:00:02,430 The following content is provided under a Creative 2 00:00:02,430 --> 00:00:03,820 Commons license. 3 00:00:03,820 --> 00:00:06,030 Your support will help MIT OpenCourseWare 4 00:00:06,030 --> 00:00:10,150 continue to offer high quality educational resources for free. 5 00:00:10,150 --> 00:00:12,690 To make a donation or to view additional materials 6 00:00:12,690 --> 00:00:16,650 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:16,650 --> 00:00:17,850 at ocw.mit.edu. 8 00:00:26,130 --> 00:00:27,880 CATHERINE DRENNAN: That's today's handout. 9 00:00:27,880 --> 00:00:31,960 We have valence bond theory and hybridization. 10 00:00:31,960 --> 00:00:33,895 So some people ask, OK, now you're 11 00:00:33,895 --> 00:00:35,770 going to tell me everything you just learned. 12 00:00:35,770 --> 00:00:36,860 It's not really right and there's 13 00:00:36,860 --> 00:00:38,068 something else that's better. 14 00:00:38,068 --> 00:00:38,590 No. 15 00:00:38,590 --> 00:00:41,200 All of these theories are good theories. 16 00:00:41,200 --> 00:00:44,140 They all do a very good job predicting the properties 17 00:00:44,140 --> 00:00:46,900 of molecules, but they all have different strengths 18 00:00:46,900 --> 00:00:47,590 and weaknesses. 19 00:00:47,590 --> 00:00:50,470 And I think in terms of what they're useful 20 00:00:50,470 --> 00:00:54,400 for, molecular orbital theory is very good in terms of thinking 21 00:00:54,400 --> 00:00:55,840 about energy levels. 22 00:00:55,840 --> 00:00:58,240 It's very good about thinking about bond orders 23 00:00:58,240 --> 00:01:00,198 or predicting whether something's going to have 24 00:01:00,198 --> 00:01:02,470 an unpaired electron or not. 25 00:01:02,470 --> 00:01:04,810 Valence bond theory and hybridization 26 00:01:04,810 --> 00:01:06,400 are really good in terms of thinking 27 00:01:06,400 --> 00:01:08,620 about shapes of molecules. 28 00:01:08,620 --> 00:01:12,010 So not so much about energy levels, but shapes. 29 00:01:12,010 --> 00:01:14,590 So all of these theories are very, very useful 30 00:01:14,590 --> 00:01:17,650 because we want to think about how atoms come together 31 00:01:17,650 --> 00:01:19,840 to form these molecules and what are the properties 32 00:01:19,840 --> 00:01:20,800 of the molecules. 33 00:01:20,800 --> 00:01:23,290 So these theories brought together really 34 00:01:23,290 --> 00:01:25,150 give us a wonderful picture of this. 35 00:01:25,150 --> 00:01:27,800 And I really like valence bond theory and hybridization 36 00:01:27,800 --> 00:01:29,490 because I like shape. 37 00:01:29,490 --> 00:01:32,890 I determine shapes of molecules, complicated molecules, 38 00:01:32,890 --> 00:01:35,800 for a living so I'm a big fan. 39 00:01:35,800 --> 00:01:40,582 But I will say that when I taught this the same lecture 40 00:01:40,582 --> 00:01:42,040 last year, I announced to the class 41 00:01:42,040 --> 00:01:46,870 that I had had a dream where all these atomic orbitals were 42 00:01:46,870 --> 00:01:50,764 coming together and trying to make other kinds of orbitals. 43 00:01:50,764 --> 00:01:52,180 And I realized that, perhaps, that 44 00:01:52,180 --> 00:01:54,280 was a sign that on Friday I should 45 00:01:54,280 --> 00:01:56,800 start teaching thermodynamics which is 46 00:01:56,800 --> 00:01:58,130 what we're going to be doing. 47 00:01:58,130 --> 00:02:00,190 We're going to start on thermodynamics on Friday. 48 00:02:00,190 --> 00:02:04,630 And last night, I had another dream about orbitals. 49 00:02:04,630 --> 00:02:10,280 So I think this is some more orbitals 50 00:02:10,280 --> 00:02:13,210 and then we go to thermodynamics. 51 00:02:13,210 --> 00:02:17,110 And I remembered my dream because at that moment, 52 00:02:17,110 --> 00:02:21,340 my giant dog jumped on top of me as I was sleeping 53 00:02:21,340 --> 00:02:24,340 to wake me up and realize that thermodynamics 54 00:02:24,340 --> 00:02:25,480 needs to come pretty soon. 55 00:02:25,480 --> 00:02:26,300 OK. 56 00:02:26,300 --> 00:02:30,760 But one more theory, valence bond. 57 00:02:30,760 --> 00:02:31,870 This is not so bad. 58 00:02:31,870 --> 00:02:33,280 OK. 59 00:02:33,280 --> 00:02:37,210 Bonds result from the pairing of unpaired electrons 60 00:02:37,210 --> 00:02:40,750 from the valence shell of atomic orbitals. 61 00:02:40,750 --> 00:02:42,190 That's it. 62 00:02:42,190 --> 00:02:43,690 That's it. 63 00:02:43,690 --> 00:02:48,180 So we have one, we bring in another 64 00:02:48,180 --> 00:02:51,400 so we can make molecular hydrogen, H2, 65 00:02:51,400 --> 00:02:53,950 because they each have one unpaired electron 66 00:02:53,950 --> 00:02:57,040 and they come together to form a bond. 67 00:02:57,040 --> 00:03:00,910 I like theories that you can put on a magnet 68 00:03:00,910 --> 00:03:02,080 on your refrigerator. 69 00:03:02,080 --> 00:03:04,750 That's a good theory to me. 70 00:03:04,750 --> 00:03:08,290 So also as part of valence bond theory, 71 00:03:08,290 --> 00:03:12,340 we have some names of bonds. 72 00:03:12,340 --> 00:03:16,390 And we've been talking about sigma molecular orbitals 73 00:03:16,390 --> 00:03:18,370 and pi molecular orbitals. 74 00:03:18,370 --> 00:03:23,500 And now, we're going to talk about sigma bonds and pi bonds. 75 00:03:23,500 --> 00:03:28,480 So we had orbitals in MO theory, valence bond theory, 76 00:03:28,480 --> 00:03:30,940 we now have bonds. 77 00:03:30,940 --> 00:03:38,050 Sigma orbital is cylindrically symmetric about the bonding 78 00:03:38,050 --> 00:03:38,950 axis. 79 00:03:38,950 --> 00:03:41,140 Thank goodness they didn't define them differently. 80 00:03:41,140 --> 00:03:42,620 That would have been a nightmare. 81 00:03:42,620 --> 00:03:46,210 So we have sigma orbitals that are cylindrically 82 00:03:46,210 --> 00:03:49,540 symmetrical about the bond axis and sigma 83 00:03:49,540 --> 00:03:52,180 bonds are cylindrically symmetrical about the bond 84 00:03:52,180 --> 00:03:52,780 axis. 85 00:03:52,780 --> 00:03:55,360 So no nodal plane along the bond axis. 86 00:03:55,360 --> 00:03:56,620 Good. 87 00:03:56,620 --> 00:03:59,530 We should be able to remember that. 88 00:03:59,530 --> 00:04:04,540 So with pi bonds, we have electron density in two lobes 89 00:04:04,540 --> 00:04:08,480 with a single nodal plane along the bond axis. 90 00:04:08,480 --> 00:04:11,890 So again, with pi orbitals, we had 91 00:04:11,890 --> 00:04:14,510 more-- it wasn't cylindrically symmetric. 92 00:04:14,510 --> 00:04:18,160 So this we should be able to remember. 93 00:04:18,160 --> 00:04:25,300 A couple other things about sigma bonds and pi bonds, 94 00:04:25,300 --> 00:04:31,280 a single bond is a sigma bond. 95 00:04:31,280 --> 00:04:34,760 So when there's one bond, it's a sigma bond. 96 00:04:34,760 --> 00:04:36,600 So what's a double bond? 97 00:04:36,600 --> 00:04:42,830 A double bond is a sigma bond plus one pi bond. 98 00:04:42,830 --> 00:04:45,190 So if it's double bond, it's got two types 99 00:04:45,190 --> 00:04:47,735 of bonds, sigma and pi. 100 00:04:47,735 --> 00:04:49,360 And what do you think a triple bond is? 101 00:04:52,950 --> 00:04:57,360 Sigma bond and two pi bonds. 102 00:04:57,360 --> 00:05:02,900 So you got a triple bond like nitrogen, you got two pi's. 103 00:05:02,900 --> 00:05:06,030 Hey, it's really a good life when you have a triple bond. 104 00:05:06,030 --> 00:05:06,530 All right. 105 00:05:06,530 --> 00:05:08,530 Single bonds always going to be sigma. 106 00:05:08,530 --> 00:05:10,240 Double, sigma and pi. 107 00:05:10,240 --> 00:05:13,380 Triple, sigma and two pi bonds. 108 00:05:13,380 --> 00:05:14,980 OK. 109 00:05:14,980 --> 00:05:19,520 So now we're going to hybridize our orbitals. 110 00:05:19,520 --> 00:05:25,000 And we're going to talk about electron promotion, as well. 111 00:05:25,000 --> 00:05:27,460 So start with carbon, carbon based life. 112 00:05:27,460 --> 00:05:31,090 Carbon is really important and if you are an organic chemist, 113 00:05:31,090 --> 00:05:34,780 and by organic, it means studying things with carbon, 114 00:05:34,780 --> 00:05:36,460 you care a lot about hybridization. 115 00:05:36,460 --> 00:05:38,001 And the stuff I'm teaching you today, 116 00:05:38,001 --> 00:05:42,160 you'll see a lot if you go on to take Organic Chemistry 512. 117 00:05:42,160 --> 00:05:46,270 So carbon, such as one in methane, so we have our methane 118 00:05:46,270 --> 00:05:48,550 molecule here. 119 00:05:48,550 --> 00:05:53,770 The carbon has four unpaired-- can form bonds 120 00:05:53,770 --> 00:05:59,740 with four electrons, but to do so we need to do something 121 00:05:59,740 --> 00:06:00,970 with our electrons. 122 00:06:00,970 --> 00:06:04,420 So carbon comes in, it has two electrons in it's 2s 123 00:06:04,420 --> 00:06:08,770 and it has two electrons in it's 2p's, p orbitals, 124 00:06:08,770 --> 00:06:11,560 but we want to form four bonds. 125 00:06:11,560 --> 00:06:14,260 And in covalent bond theory, every bond 126 00:06:14,260 --> 00:06:16,630 you bring an electron from one atom, 127 00:06:16,630 --> 00:06:18,760 an electron from the other, and they pair 128 00:06:18,760 --> 00:06:20,110 and that forms a bond. 129 00:06:20,110 --> 00:06:25,330 So we don't have four unpaired electrons to make four bonds 130 00:06:25,330 --> 00:06:27,820 with this configuration of electrons, 131 00:06:27,820 --> 00:06:32,740 so we can talk about promotion of an electron from here 132 00:06:32,740 --> 00:06:34,120 up there. 133 00:06:34,120 --> 00:06:39,850 And if we do that , now we have our four single unpaired 134 00:06:39,850 --> 00:06:42,460 electrons ready to make four bonds. 135 00:06:42,460 --> 00:06:44,620 And carbon does like to make four bonds. 136 00:06:44,620 --> 00:06:46,480 It does it quite often. 137 00:06:46,480 --> 00:06:49,240 So that's electron promotion. 138 00:06:49,240 --> 00:06:51,850 To form those four bonds, a 2s electron 139 00:06:51,850 --> 00:06:56,470 is promoted to an empty 2p orbital. 140 00:06:56,470 --> 00:07:00,920 And then, we can hybridized our orbitals 141 00:07:00,920 --> 00:07:04,180 and that means that we want to give all our orbitals 142 00:07:04,180 --> 00:07:07,900 some s and some p character. 143 00:07:07,900 --> 00:07:12,250 So here are our hybrid orbitals and let 144 00:07:12,250 --> 00:07:14,050 me show you the nomenclature. 145 00:07:14,050 --> 00:07:16,085 So we're talking about n equals two. 146 00:07:16,085 --> 00:07:17,470 So we have a two. 147 00:07:17,470 --> 00:07:21,280 We have s character and we have p character 148 00:07:21,280 --> 00:07:26,050 and we're using three p orbitals to make our hybrid orbitals. 149 00:07:26,050 --> 00:07:31,870 So we are going to make a 2sp 3 hybrid orbital. 150 00:07:31,870 --> 00:07:33,670 And we're going to make four of them 151 00:07:33,670 --> 00:07:37,560 because we've used four atomic orbitals to make them. 152 00:07:37,560 --> 00:07:42,520 So if we are using four, we need to make four. 153 00:07:42,520 --> 00:07:45,800 So let's kind of take a look at what's going on here. 154 00:07:45,800 --> 00:07:49,090 And we'll say that these molecular orbitals differ only 155 00:07:49,090 --> 00:07:52,150 in terms of their orientation in space. 156 00:07:52,150 --> 00:07:53,650 So they don't have different shapes, 157 00:07:53,650 --> 00:07:56,600 they're just oriented differently. 158 00:07:56,600 --> 00:08:01,930 So here we have our 2s, remember it's symmetric, 159 00:08:01,930 --> 00:08:06,880 and we have our three p orbitals, 160 00:08:06,880 --> 00:08:09,190 and they're all the same except that they're all 161 00:08:09,190 --> 00:08:12,650 oriented differently in space. 162 00:08:12,650 --> 00:08:15,310 And when we bring these together, 163 00:08:15,310 --> 00:08:20,560 we form four hybrid orbitals and they kind of look like turtles, 164 00:08:20,560 --> 00:08:23,950 but they're turtles oriented differently in space, 165 00:08:23,950 --> 00:08:27,610 but otherwise they're the same. 166 00:08:27,610 --> 00:08:34,000 So those are our sp 3 hybridized orbitals. 167 00:08:34,000 --> 00:08:40,570 So carbon has this sp 3 hybridized orbital 168 00:08:40,570 --> 00:08:43,480 and it has four unpaired electrons 169 00:08:43,480 --> 00:08:49,430 available to form bonds with four hydrogens. 170 00:08:49,430 --> 00:08:53,140 So let's bring our hydrogens in to form our bonds. 171 00:08:53,140 --> 00:08:58,490 And each hydrogen brings with it it's one electron. 172 00:08:58,490 --> 00:09:02,020 So now we have two electrons in all four 173 00:09:02,020 --> 00:09:03,490 of our hybrid orbitals. 174 00:09:09,160 --> 00:09:12,724 And we can think about where the energy came from. 175 00:09:12,724 --> 00:09:14,890 I just moved that electron, I didn't think about it. 176 00:09:14,890 --> 00:09:16,930 I'm like, yeah, that just goes up here. 177 00:09:16,930 --> 00:09:21,070 So where did the energy come from to do that? 178 00:09:21,070 --> 00:09:23,800 And that is, it came from bonding. 179 00:09:23,800 --> 00:09:28,660 So this molecule now is more stable because it's bonded. 180 00:09:28,660 --> 00:09:30,880 Methane isn't quite a stable molecule. 181 00:09:30,880 --> 00:09:33,290 That's another problem in and of itself. 182 00:09:33,290 --> 00:09:35,350 So the bonding allows you to do that. 183 00:09:35,350 --> 00:09:38,830 You get back from this bonding. 184 00:09:38,830 --> 00:09:40,840 So let's look at those bonds then 185 00:09:40,840 --> 00:09:45,800 that are formed that make that electron promotion worthwhile. 186 00:09:45,800 --> 00:09:49,240 And so you're forming a bond between the carbon 187 00:09:49,240 --> 00:09:51,760 and the hydrogen, you're forming for them, 188 00:09:51,760 --> 00:09:55,930 and you're forming single bonds, they're sigma bonds, 189 00:09:55,930 --> 00:10:02,110 and the bond is formed between the carbon's 2sp 3 orbital 190 00:10:02,110 --> 00:10:04,780 and the hydrogen's 1s orbital. 191 00:10:04,780 --> 00:10:10,030 Hydrogen can't hybridize, it's got one, 1s orbital. 192 00:10:10,030 --> 00:10:13,250 That's all it's got, can't do anything else. 193 00:10:13,250 --> 00:10:16,500 And that gives you a bond then, a sigma bond, 194 00:10:16,500 --> 00:10:20,630 that you'll see this a lot and you'll write this a lot. 195 00:10:20,630 --> 00:10:23,804 This is how we're going to name that sigma bond. 196 00:10:23,804 --> 00:10:24,970 So we're going to say sigma. 197 00:10:24,970 --> 00:10:26,950 We're going to have a parentheses. 198 00:10:26,950 --> 00:10:29,290 Identify the element, it's carbon. 199 00:10:29,290 --> 00:10:30,850 N is 2. 200 00:10:30,850 --> 00:10:35,980 Type of orbital, sp 3 comma hydrogen, 201 00:10:35,980 --> 00:10:40,620 the name of the other element, and it's orbital, which is 1s. 202 00:10:40,620 --> 00:10:45,050 So when it ask you to name the type of bond, 203 00:10:45,050 --> 00:10:48,360 this Is the complete answer that we're looking for. 204 00:10:48,360 --> 00:10:50,214 And we'll have more practice on this. 205 00:10:53,140 --> 00:10:54,960 Now we can also think about the shape 206 00:10:54,960 --> 00:10:57,010 that this molecule would have. 207 00:10:57,010 --> 00:11:01,780 What is the angle here between this hydrogen and that hydrogen 208 00:11:01,780 --> 00:11:07,200 and frankly, between any of the hydrogen carbon hydrogens? 209 00:11:07,200 --> 00:11:10,830 Yup, 109.5. 210 00:11:10,830 --> 00:11:14,290 And the name of that geometry? 211 00:11:14,290 --> 00:11:16,950 Tetrahedral, right. 212 00:11:16,950 --> 00:11:25,320 So sp 3 gives you a tetrahedral based geometry here. 213 00:11:25,320 --> 00:11:25,950 All right. 214 00:11:25,950 --> 00:11:28,460 So now let's get more complicated. 215 00:11:28,460 --> 00:11:29,970 Let's bring two carbons in. 216 00:11:29,970 --> 00:11:34,120 So we have ethane, two carbon's, six hydrogens. 217 00:11:34,120 --> 00:11:39,160 So this also has its carbons are sp three, 218 00:11:39,160 --> 00:11:41,530 and this is what we saw before for methane, 219 00:11:41,530 --> 00:11:46,320 but now I'm going to rotate this around and that's one carbon, 220 00:11:46,320 --> 00:11:49,900 but we need another carbon, but first we 221 00:11:49,900 --> 00:11:52,150 can think about this one carbon. 222 00:11:52,150 --> 00:11:57,040 So one of the carbons of, ethane it would have this 109.5 angle. 223 00:11:57,040 --> 00:12:01,000 It has four unpaired electrons available in it's four 224 00:12:01,000 --> 00:12:06,130 hybrid orbitals to form interactions, one with carbon 225 00:12:06,130 --> 00:12:09,100 and three of them with hydrogen. And then we 226 00:12:09,100 --> 00:12:12,550 need another one of these so we'll bring that in 227 00:12:12,550 --> 00:12:16,120 and it comes in with its set of hybrid orbitals 228 00:12:16,120 --> 00:12:20,070 and it's set of electrons. 229 00:12:20,070 --> 00:12:22,800 And we form a bond between them. 230 00:12:22,800 --> 00:12:27,287 And the bond we're going to form is a single bond, a sigma bond. 231 00:12:30,120 --> 00:12:32,900 And now let's bring in our hydrogens. 232 00:12:32,900 --> 00:12:35,525 So we had six hydrogens, three for each carbon. 233 00:12:38,970 --> 00:12:41,220 And so there are now two types of bonds. 234 00:12:41,220 --> 00:12:44,140 We have the carbon-carbon bond and we also 235 00:12:44,140 --> 00:12:47,650 have the carbon-hydrogen bonds. 236 00:12:47,650 --> 00:12:51,100 And so the carbon-carbon bond, which is a sigma bond, 237 00:12:51,100 --> 00:12:58,090 is sigma (C-- it has carbon-- 2sp 3, 238 00:12:58,090 --> 00:13:02,900 the other carbon is the same, C2sp 3 and then the bracket. 239 00:13:02,900 --> 00:13:04,270 So that's that sigma bond. 240 00:13:04,270 --> 00:13:07,030 It's a single bond. 241 00:13:07,030 --> 00:13:10,360 And here is our ethane molecule. 242 00:13:13,240 --> 00:13:16,590 And then we have our carbon hydrogen bonds, 243 00:13:16,590 --> 00:13:18,100 they're also sigma. 244 00:13:18,100 --> 00:13:21,250 Please don't give me pi bonds to hydrogen. It only 245 00:13:21,250 --> 00:13:23,744 has that one electron tapping with two electrons. 246 00:13:23,744 --> 00:13:25,410 It doesn't want do anything complicated. 247 00:13:25,410 --> 00:13:27,710 It doesn't have p orbitals, just that one s. 248 00:13:27,710 --> 00:13:32,305 So sigma C2sp 3, H1s. 249 00:13:35,070 --> 00:13:37,000 And now we have defined this molecule 250 00:13:37,000 --> 00:13:41,140 so we brought together two tetrahedral centers 251 00:13:41,140 --> 00:13:46,300 and formed this molecule with a single bond. 252 00:13:46,300 --> 00:13:48,720 So let's talk about nitrogen. Nitrogen, 253 00:13:48,720 --> 00:13:52,280 also again, very important. 254 00:13:52,280 --> 00:13:55,920 So here we have five valence electrons. 255 00:13:55,920 --> 00:13:58,340 What about electron promotion? 256 00:13:58,340 --> 00:14:00,522 Should I do it? 257 00:14:00,522 --> 00:14:02,460 No. 258 00:14:02,460 --> 00:14:04,270 Because I mean, you could put it up here, 259 00:14:04,270 --> 00:14:07,800 but it can't make any more bonds so it doesn't really matter. 260 00:14:07,800 --> 00:14:10,320 So it doesn't occur because it would not 261 00:14:10,320 --> 00:14:13,950 increase the number of unpaired electrons to form bonds, 262 00:14:13,950 --> 00:14:18,160 but we can hybridize. 263 00:14:18,160 --> 00:14:21,210 So we can still hybridize our orbitals 264 00:14:21,210 --> 00:14:24,370 and we can get four hybrid orbitals, 265 00:14:24,370 --> 00:14:26,430 because we're going to use our 2s 266 00:14:26,430 --> 00:14:29,800 and all three of our 2p orbitals. 267 00:14:29,800 --> 00:14:32,770 So we'll get the same set of hybrid orbitals. 268 00:14:32,770 --> 00:14:36,520 But this time, one of them has two electrons in it. 269 00:14:36,520 --> 00:14:38,290 So it's not ready to bond, it's happy 270 00:14:38,290 --> 00:14:40,090 according to valence bond theory. 271 00:14:40,090 --> 00:14:42,990 And these are our alone pairs. 272 00:14:42,990 --> 00:14:47,080 But we can form three bonds with these guys 273 00:14:47,080 --> 00:14:52,150 so let's look at an example, NH3. 274 00:14:52,150 --> 00:14:56,650 So now we have our lone pair, it's in this orbital up here, 275 00:14:56,650 --> 00:15:00,210 and then we have three orbitals available for bonding, 276 00:15:00,210 --> 00:15:04,180 each with an unpaired electron ready for the three 277 00:15:04,180 --> 00:15:06,340 atoms of hydrogen to come in. 278 00:15:06,340 --> 00:15:09,760 So we bring in our three atoms of hydrogen, 279 00:15:09,760 --> 00:15:14,020 each came with an electron, and now 280 00:15:14,020 --> 00:15:17,490 you can tell me with a clicker about the angle 281 00:15:17,490 --> 00:15:19,912 and the geometry of this molecule. 282 00:15:32,700 --> 00:15:34,200 Let's just do 10 more seconds. 283 00:15:54,430 --> 00:15:56,870 All right. 284 00:15:56,870 --> 00:16:00,860 So this is back to VSEPR again. 285 00:16:00,860 --> 00:16:03,230 So we have an angle here. 286 00:16:03,230 --> 00:16:07,430 It's based on an sn 4 system, one lone pair, three bonded 287 00:16:07,430 --> 00:16:08,400 atoms. 288 00:16:08,400 --> 00:16:12,350 So it's based on our 109.5, but those lone pairs 289 00:16:12,350 --> 00:16:14,030 make for bad roommates and they're 290 00:16:14,030 --> 00:16:17,240 pressing all of these hydrogens together 291 00:16:17,240 --> 00:16:20,210 and so the angle is less than 109.5 292 00:16:20,210 --> 00:16:23,630 and we name this structure based on the atoms 293 00:16:23,630 --> 00:16:28,250 we see, not the lone pairs, so this is trigonal pyramidal. 294 00:16:28,250 --> 00:16:31,640 And so here we have it here so we're naming it 295 00:16:31,640 --> 00:16:35,480 without thinking about the position of those lone pairs 296 00:16:35,480 --> 00:16:39,200 that are pressing down on the bond so it looks trigonal, 297 00:16:39,200 --> 00:16:41,688 like a triangle, but it's also a little pyramid. 298 00:16:44,240 --> 00:16:48,530 So VSEPR-- VSEPR and hybridization, they just 299 00:16:48,530 --> 00:16:49,400 go right together. 300 00:16:49,400 --> 00:16:50,180 It's awesome. 301 00:16:50,180 --> 00:16:51,230 OK. 302 00:16:51,230 --> 00:16:53,960 So we can also name the type of bond. 303 00:16:53,960 --> 00:17:00,860 So our nitrogen had 2sp 3 hybridization and our hydrogen 304 00:17:00,860 --> 00:17:04,250 just 1s, it's a sigma bond, it's a single bond. 305 00:17:04,250 --> 00:17:10,159 So we named that sigma N2sp 3, H1s. 306 00:17:14,420 --> 00:17:19,220 So nitrogen, now we're going to go back to carbon-- 307 00:17:19,220 --> 00:17:25,750 sorry, to oxygen-- and think about hybridization of oxygen. 308 00:17:25,750 --> 00:17:30,290 Oxygen. Should I do an electron promotion? 309 00:17:30,290 --> 00:17:30,790 No. 310 00:17:30,790 --> 00:17:31,873 It's not going to help me. 311 00:17:31,873 --> 00:17:36,140 It's not going create any more electrons available to form 312 00:17:36,140 --> 00:17:41,690 bonds, but I can hybridize and I can get the same four 313 00:17:41,690 --> 00:17:47,870 hybrid orbitals, our four 2sp 3 orbitals, but now two of them 314 00:17:47,870 --> 00:17:51,140 have two electrons in them and two 315 00:17:51,140 --> 00:17:54,770 are available to form bonds. 316 00:17:54,770 --> 00:17:59,690 Oxygen loves to form bonds with hydrogen and form water, 317 00:17:59,690 --> 00:18:01,100 most of the planet is water. 318 00:18:01,100 --> 00:18:04,460 There's a lot of water and water is really important for life 319 00:18:04,460 --> 00:18:08,480 so it's great that oxygen and hydrogen get along so well. 320 00:18:08,480 --> 00:18:12,590 So the oxygen, again, has two lone pairs which are here. 321 00:18:12,590 --> 00:18:16,910 You bring in our hydrogens and they come with one electron. 322 00:18:16,910 --> 00:18:21,500 And again, now, it's still a steric number of four systems, 323 00:18:21,500 --> 00:18:25,760 so it's less than 109.5, and it's actually a lot less 324 00:18:25,760 --> 00:18:28,490 than the nitrogen because you have those two lone pairs that 325 00:18:28,490 --> 00:18:32,000 are just taken up so much room and squeezing together 326 00:18:32,000 --> 00:18:38,780 these hydrogen atoms over here creating this 104.5 angle. 327 00:18:38,780 --> 00:18:41,960 So here we have our oxygen molecule 328 00:18:41,960 --> 00:18:45,560 with its two lone pairs and its two hydrogens, 329 00:18:45,560 --> 00:18:48,890 and what's the name of that geometry? 330 00:18:48,890 --> 00:18:50,182 Bent. 331 00:18:50,182 --> 00:18:52,785 And again, we have these polar bonds 332 00:18:52,785 --> 00:18:55,820 that create a dipole so it's a polar molecule, which 333 00:18:55,820 --> 00:18:58,640 is very important in life. 334 00:18:58,640 --> 00:19:02,090 And we can name that bond. 335 00:19:02,090 --> 00:19:04,490 It's a sigma bond. 336 00:19:04,490 --> 00:19:09,215 It's made up of oxygen O2sp 2, H1s. 337 00:19:11,911 --> 00:19:12,410 All right. 338 00:19:12,410 --> 00:19:17,090 So that's sp 3 hybridization. 339 00:19:17,090 --> 00:19:23,900 Now let's talk about sp 2 hybridization. 340 00:19:23,900 --> 00:19:27,920 So sp 2 hybridization. 341 00:19:27,920 --> 00:19:32,720 So back to our atomic orbitals. 342 00:19:32,720 --> 00:19:36,380 And now, we're not going hybridized all of our orbitals. 343 00:19:36,380 --> 00:19:42,260 We're just going hybridize our 2s and two of our p orbitals. 344 00:19:42,260 --> 00:19:45,590 So we'll hybridized these guys and we 345 00:19:45,590 --> 00:19:51,140 will form three hybrid orbitals and we will still 346 00:19:51,140 --> 00:19:54,080 have one un-hybridized orbital. 347 00:19:54,080 --> 00:20:00,230 We will have 2p y left alone. 348 00:20:00,230 --> 00:20:02,210 So let's see what this does. 349 00:20:02,210 --> 00:20:06,810 How is this hybridization useful? 350 00:20:06,810 --> 00:20:08,936 So let's talk about boron. 351 00:20:08,936 --> 00:20:13,160 Boron has three unpaired electrons, 352 00:20:13,160 --> 00:20:16,670 but they are not all available right now to form bonds, 353 00:20:16,670 --> 00:20:18,840 according to valence bond theory. 354 00:20:18,840 --> 00:20:22,820 So here we do want to do an electron promotion 355 00:20:22,820 --> 00:20:27,170 to put one of them up here so that now all three 356 00:20:27,170 --> 00:20:29,970 are available to form bonds. 357 00:20:29,970 --> 00:20:35,120 And we can again, hybridize these three atomic orbitals 358 00:20:35,120 --> 00:20:38,150 and form three hybrid orbitals. 359 00:20:38,150 --> 00:20:43,260 So we have three 2sp 2 hybrid orbitals 360 00:20:43,260 --> 00:20:46,600 and then we still have our 2 py orbitals 361 00:20:46,600 --> 00:20:48,060 so don't forget to mark it. 362 00:20:48,060 --> 00:20:49,230 It seems lonely. 363 00:20:49,230 --> 00:20:52,630 It's over here, but it's going to be important later 364 00:20:52,630 --> 00:20:54,970 so don't feel bad for it, yet. 365 00:20:54,970 --> 00:20:55,470 All right. 366 00:20:55,470 --> 00:20:58,670 So boron-- let's think about these hybrid orbitals 367 00:20:58,670 --> 00:21:01,230 and how this gives us the structure that we 368 00:21:01,230 --> 00:21:04,750 know occurs when we have boron. 369 00:21:04,750 --> 00:21:09,150 So boron now has its three sp 2 orbitals and these are going 370 00:21:09,150 --> 00:21:11,940 to lie in a plane and they're going 371 00:21:11,940 --> 00:21:13,740 to be as far apart from each other 372 00:21:13,740 --> 00:21:16,880 as they can to minimize electron repulsion. 373 00:21:16,880 --> 00:21:18,690 And if you're in a plane, then you 374 00:21:18,690 --> 00:21:23,010 need-- far apart as you could be is 120 degrees. 375 00:21:23,010 --> 00:21:26,220 And this is what gives us our trigonal planar geometry. 376 00:21:26,220 --> 00:21:29,820 So we saw that boron formed these trigonal planar complexes 377 00:21:29,820 --> 00:21:34,880 before and again, they're trigonal planar because they're 378 00:21:34,880 --> 00:21:40,910 like a triangle and they're in a plane, trigonal planar. 379 00:21:40,910 --> 00:21:44,390 And we can now bring in our hydrogens. 380 00:21:44,390 --> 00:21:47,520 The hydrogens come with an electron 381 00:21:47,520 --> 00:21:50,850 so we have an electron for them and there we 382 00:21:50,850 --> 00:21:52,950 have our structure. 383 00:21:52,950 --> 00:21:55,420 We can also name that bond. 384 00:21:55,420 --> 00:21:57,670 So again we have single bonds. 385 00:21:57,670 --> 00:22:04,460 So sigma B, for boron, 2sp 2, H1s, and there 386 00:22:04,460 --> 00:22:07,620 are three of those. 387 00:22:07,620 --> 00:22:10,680 Carbon-- carbon can also do this. 388 00:22:10,680 --> 00:22:14,460 We talked about carbon being sp 3. 389 00:22:14,460 --> 00:22:18,120 Carbon can also be sp 2. 390 00:22:18,120 --> 00:22:21,140 Hybridized carbon is amazing that's why 391 00:22:21,140 --> 00:22:23,520 life is based on carbon. 392 00:22:23,520 --> 00:22:25,870 Carbon can do lots of things. 393 00:22:25,870 --> 00:22:28,160 So again, we're going hybridized two p orbitals, 394 00:22:28,160 --> 00:22:32,340 one s orbital to give three hybrid orbitals 395 00:22:32,340 --> 00:22:36,270 and we have our 2py over here in the corner, 396 00:22:36,270 --> 00:22:40,210 but don't feel bad for it, it's going to do something useful. 397 00:22:40,210 --> 00:22:44,180 So we now have three electrons in these hybrid orbitals 398 00:22:44,180 --> 00:22:50,220 and now we have one electron in our 2py un-hybridized orbital, 399 00:22:50,220 --> 00:22:51,370 as well. 400 00:22:51,370 --> 00:22:54,300 So let's see what carbon, with this kind of arrangement 401 00:22:54,300 --> 00:22:57,180 of orbitals, can do. 402 00:22:57,180 --> 00:23:01,680 And again, we're going to have trigonal planar geometry 403 00:23:01,680 --> 00:23:05,820 for our 2sp 2 hybrid orbitals. 404 00:23:05,820 --> 00:23:09,030 So we have carbon there and these are all in a plane, 405 00:23:09,030 --> 00:23:14,610 but now coming out of a plane toward us is this 2py orbital. 406 00:23:14,610 --> 00:23:19,160 So it's coming out 90 degrees away from the trigonal planar 407 00:23:19,160 --> 00:23:21,410 geometry. 408 00:23:21,410 --> 00:23:24,840 So an example of sp 2 hybridization 409 00:23:24,840 --> 00:23:28,530 is in this molecule, C2H4, and it 410 00:23:28,530 --> 00:23:32,310 has a double bond, which means if it's a double bond, 411 00:23:32,310 --> 00:23:35,220 it has what kind of bonds in it? 412 00:23:35,220 --> 00:23:37,560 Sigma and pi, right. 413 00:23:37,560 --> 00:23:41,470 So one sigma, one pi bond. 414 00:23:41,470 --> 00:23:44,552 So here now, and this is the trigonal planar geometry. 415 00:23:44,552 --> 00:23:47,010 It's supposed to be in a plane, but you can't really see it 416 00:23:47,010 --> 00:23:48,360 if it's really in a plane. 417 00:23:48,360 --> 00:23:53,510 But 90 degrees away from that plane is our 2py orbital. 418 00:23:53,510 --> 00:23:57,030 We brought in our two hydrogens so this carbon here, is carbon 419 00:23:57,030 --> 00:23:59,695 is there, two hydrogens are there. 420 00:23:59,695 --> 00:24:02,590 This would be 120 degrees. 421 00:24:02,590 --> 00:24:04,260 Now we're going to bring in another one. 422 00:24:04,260 --> 00:24:05,820 That's the one over here. 423 00:24:05,820 --> 00:24:07,125 It comes in with it's carbon. 424 00:24:07,125 --> 00:24:10,380 It comes in with it's two hydrogens forming 425 00:24:10,380 --> 00:24:13,710 these single bond, sigma bonds, between the carbon 426 00:24:13,710 --> 00:24:15,360 and those hydrogens. 427 00:24:15,360 --> 00:24:18,450 And now we're going to form a carbon-carbon bond. 428 00:24:18,450 --> 00:24:26,610 This carbon-carbon bond is a sigma bond and so it's C2sp 2, 429 00:24:26,610 --> 00:24:29,900 C2sp 2, but we're not done. 430 00:24:29,900 --> 00:24:34,100 We said this is a double bond, so that's our sigma bond, 431 00:24:34,100 --> 00:24:36,240 but we need our pi bond. 432 00:24:36,240 --> 00:24:41,220 And now py, our un-hybridized orbital, 433 00:24:41,220 --> 00:24:45,780 is extremely excited because it can form the pi bond. 434 00:24:45,780 --> 00:24:49,050 So we form a pi bond and that's formed 435 00:24:49,050 --> 00:24:57,660 by our C2py, C2py un-hybridized orbital. 436 00:24:57,660 --> 00:25:03,930 And we also have four CH bonds and those are single bonds, 437 00:25:03,930 --> 00:25:06,870 those are sigma bonds, and so they're 438 00:25:06,870 --> 00:25:14,260 formed by our C2sp 2 carbon and hydrogen 1s. 439 00:25:14,260 --> 00:25:15,970 And there are four of those. 440 00:25:15,970 --> 00:25:20,440 So that's an example of sp 2 hybridization. 441 00:25:20,440 --> 00:25:22,090 And one thing that's very important, 442 00:25:22,090 --> 00:25:25,840 and here you can see what that molecule looks 443 00:25:25,840 --> 00:25:28,737 like-- doesn't all fall apart-- so this is a double bond, 444 00:25:28,737 --> 00:25:30,820 these smaller kits don't let me make double bonds, 445 00:25:30,820 --> 00:25:33,490 so I have a sign double bond. 446 00:25:33,490 --> 00:25:38,050 And you can see the angles and the geometry of this molecule. 447 00:25:38,050 --> 00:25:40,510 And another property of something 448 00:25:40,510 --> 00:25:43,390 with the double bond like this is that it's not 449 00:25:43,390 --> 00:25:45,040 really free to rotate. 450 00:25:45,040 --> 00:25:47,800 So when you have these two kind of points of attachment, 451 00:25:47,800 --> 00:25:50,290 when we have these orbitals forming 452 00:25:50,290 --> 00:25:54,370 between your on hybridized p orbitals, 453 00:25:54,370 --> 00:25:58,330 that does not allow for rotation around the double bond. 454 00:25:58,330 --> 00:26:00,670 So if you're an organic chemist wanting 455 00:26:00,670 --> 00:26:03,040 to make a molecule that's going to be rigid, 456 00:26:03,040 --> 00:26:05,320 if you put a lot of double bonds in it, 457 00:26:05,320 --> 00:26:07,600 it can't twist and turn very well. 458 00:26:07,600 --> 00:26:10,510 It's often very rigid which is useful. 459 00:26:10,510 --> 00:26:13,690 So we'll stop here and we'll finish up 460 00:26:13,690 --> 00:26:19,120 on Friday sp 2 hybridization. 461 00:26:19,120 --> 00:26:22,270 For the clicker question, the bone over there on that 462 00:26:22,270 --> 00:26:24,730 is also the same as the one on the board. 463 00:26:24,730 --> 00:26:27,940 The one on the board is written with atoms in it 464 00:26:27,940 --> 00:26:32,680 and it has squiggly lines to abbreviate so make sure 465 00:26:32,680 --> 00:26:35,590 that your answer is consistent with the picture on the board, 466 00:26:35,590 --> 00:26:36,240 as well. 467 00:26:45,500 --> 00:26:46,960 How we doing? 468 00:26:46,960 --> 00:26:47,511 OK. 469 00:26:47,511 --> 00:26:48,010 All right. 470 00:26:48,010 --> 00:26:50,710 Let's just take 10 more seconds. 471 00:26:50,710 --> 00:26:53,390 Remember this is a clicker competition 472 00:26:53,390 --> 00:26:58,190 so we want to get the right answer in for your recitation. 473 00:26:58,190 --> 00:27:00,690 AUDIENCE: [SIDE CONVERSATIONS] 474 00:27:08,920 --> 00:27:11,740 CATHERINE DRENNAN: All right. 475 00:27:11,740 --> 00:27:15,910 That's pretty good because that's the right answer. 476 00:27:15,910 --> 00:27:16,660 OK. 477 00:27:16,660 --> 00:27:20,470 So let's just take a look at this for a minute. 478 00:27:20,470 --> 00:27:22,160 First let me explain. 479 00:27:22,160 --> 00:27:24,700 Let's settle down, quiet down. 480 00:27:24,700 --> 00:27:27,130 Let me just explain the diagram, too, 481 00:27:27,130 --> 00:27:31,300 because you'll be seeing these diagrams. 482 00:27:31,300 --> 00:27:35,440 So when you just have a bond, a line, 483 00:27:35,440 --> 00:27:40,420 and there's no atom indicated, that means it's carbon. 484 00:27:40,420 --> 00:27:43,170 Organic chemists, I think, came up with this rule. 485 00:27:43,170 --> 00:27:45,760 Carbon, they just said if nothing's indicated, of course, 486 00:27:45,760 --> 00:27:46,390 it's carbon. 487 00:27:46,390 --> 00:27:48,490 Carbon is such an important element, 488 00:27:48,490 --> 00:27:52,000 we don't really need to say more about it than that. 489 00:27:52,000 --> 00:27:54,320 So you could interpret this diagram, 490 00:27:54,320 --> 00:27:57,710 you have a carbon double bonded to another carbon. 491 00:27:57,710 --> 00:27:59,740 And then up here, there's a carbon 492 00:27:59,740 --> 00:28:03,100 in that ring so I just put, in this diagram, 493 00:28:03,100 --> 00:28:05,710 carbon with squigglies, you'll see that sometimes. 494 00:28:05,710 --> 00:28:08,020 That means that there's more atoms there, 495 00:28:08,020 --> 00:28:10,690 but I'm too lazy to draw them. 496 00:28:10,690 --> 00:28:12,816 And on this side, there's a carbon, 497 00:28:12,816 --> 00:28:15,190 but there's more atoms there and I'm too lazy to draw it, 498 00:28:15,190 --> 00:28:16,680 another squiggly. 499 00:28:16,680 --> 00:28:19,660 And then we have the double bond so there's a carbon down here, 500 00:28:19,660 --> 00:28:20,320 as well. 501 00:28:20,320 --> 00:28:23,080 It wasn't indicated, just the line in the drawing. 502 00:28:23,080 --> 00:28:27,010 And you have to predict how many hydrogens Hydrogens are often 503 00:28:27,010 --> 00:28:28,420 not indicated. 504 00:28:28,420 --> 00:28:29,560 This one is indicated. 505 00:28:29,560 --> 00:28:31,270 There are other hydrogens in this drawing 506 00:28:31,270 --> 00:28:32,860 that are not indicated. 507 00:28:32,860 --> 00:28:35,680 You need to figure out where they go 508 00:28:35,680 --> 00:28:38,620 and the material we're doing now is going to help you do that. 509 00:28:38,620 --> 00:28:41,140 And then I also drew something and another squiggly 510 00:28:41,140 --> 00:28:43,390 because I was too lazy to draw the rest. 511 00:28:43,390 --> 00:28:46,090 So these are different kinds of diagrams 512 00:28:46,090 --> 00:28:48,460 that you'll see that all kind of mean 513 00:28:48,460 --> 00:28:50,290 there's more than one way to kind of write 514 00:28:50,290 --> 00:28:53,840 the same structure. 515 00:28:53,840 --> 00:28:59,320 So this particular molecule was used to treat schizophrenia 516 00:28:59,320 --> 00:29:05,050 in the 1950s and key to the usefulness of the molecule 517 00:29:05,050 --> 00:29:06,610 was that double bond. 518 00:29:06,610 --> 00:29:10,390 As we talked about last time, double bonds restrict movement. 519 00:29:10,390 --> 00:29:12,580 You can't twist around the double bond. 520 00:29:12,580 --> 00:29:16,750 And so if you had exchange and you had this group over there 521 00:29:16,750 --> 00:29:20,170 and the hydrogen over here, it wouldn't be an active molecule. 522 00:29:20,170 --> 00:29:23,860 So this double bond fixes the orientation 523 00:29:23,860 --> 00:29:26,680 of those other atoms such that it was an active molecule 524 00:29:26,680 --> 00:29:29,860 and could be used as a pharmaceutical 525 00:29:29,860 --> 00:29:31,640 to treat schizophrenia. 526 00:29:31,640 --> 00:29:33,760 So in terms of the bonds then, we 527 00:29:33,760 --> 00:29:36,820 have a double bond which means we have one sigma and one pi 528 00:29:36,820 --> 00:29:37,630 bond. 529 00:29:37,630 --> 00:29:40,420 And so the sigma bond down here, we 530 00:29:40,420 --> 00:29:43,720 had to know what the hybridization was. 531 00:29:43,720 --> 00:29:49,360 And here, those carbons are bonded to three other atoms 532 00:29:49,360 --> 00:29:55,440 and so it would be sp 2 carbons and also with the double bond 533 00:29:55,440 --> 00:29:56,620 sp 2. 534 00:29:56,620 --> 00:29:59,260 And then we also have a pi bond and pi 535 00:29:59,260 --> 00:30:05,560 bonds are made up of non-hybridized orbitals, our py 536 00:30:05,560 --> 00:30:07,090 or our px. 537 00:30:07,090 --> 00:30:09,910 And so those are the ones that make up the pi bond. 538 00:30:09,910 --> 00:30:11,800 In all the other variations, some 539 00:30:11,800 --> 00:30:15,580 you had two sigmas, that's not right, we have a sigma and a pi 540 00:30:15,580 --> 00:30:16,900 so most people figure that out. 541 00:30:16,900 --> 00:30:20,830 They picked the ones that had those categories for the most 542 00:30:20,830 --> 00:30:21,886 part. 543 00:30:21,886 --> 00:30:23,260 And then you had to pay attention 544 00:30:23,260 --> 00:30:26,620 to whether it was sp 2 or sp 3. 545 00:30:26,620 --> 00:30:30,650 And then here, this one, the pi bond 546 00:30:30,650 --> 00:30:32,710 is not made up of hybridized orbitals, 547 00:30:32,710 --> 00:30:35,240 it's made up of the atomic orbital leftover. 548 00:30:35,240 --> 00:30:38,540 So a lot to look at that particular problem, 549 00:30:38,540 --> 00:30:42,380 but this is really good practice for the exam, which is 550 00:30:42,380 --> 00:30:44,860 coming up a week from Monday. 551 00:30:44,860 --> 00:30:48,520 There's going to be lots of hybridization and today, 552 00:30:48,520 --> 00:30:51,380 we're going to post extra problems for the exam 553 00:30:51,380 --> 00:30:53,110 so you have, really, a whole week 554 00:30:53,110 --> 00:30:55,300 to start getting ready for this exam 555 00:30:55,300 --> 00:30:57,820 and to keep up with the new material. 556 00:30:57,820 --> 00:31:00,670 And so extra problems and an old exam 557 00:31:00,670 --> 00:31:03,441 are also going to be posted later today. 558 00:31:03,441 --> 00:31:03,940 All right. 559 00:31:03,940 --> 00:31:06,670 So let's just finish with hybridization now 560 00:31:06,670 --> 00:31:09,190 and this is good because this is all stuff that's 561 00:31:09,190 --> 00:31:10,510 going to be on the exam. 562 00:31:10,510 --> 00:31:13,480 And also, the instructions for the exam 563 00:31:13,480 --> 00:31:17,290 are attached to today's handouts and, of course, 564 00:31:17,290 --> 00:31:19,904 remember no makeup exams and clicker competition. 565 00:31:19,904 --> 00:31:21,820 So I'm not really going to go through anything 566 00:31:21,820 --> 00:31:22,660 in the instructions. 567 00:31:22,660 --> 00:31:26,260 It's very similar to last time so you can take a look at that 568 00:31:26,260 --> 00:31:29,140 and see on the material, the material 569 00:31:29,140 --> 00:31:32,170 starts with the periodic table, periodic trends, 570 00:31:32,170 --> 00:31:34,090 and goes through the material that I'm 571 00:31:34,090 --> 00:31:36,710 going to finish with partway through today's lecture. 572 00:31:36,710 --> 00:31:38,800 So at the end of hybridization, that's 573 00:31:38,800 --> 00:31:42,100 the end of exam two material. 574 00:31:42,100 --> 00:31:44,800 So we're going to finish our lecture notes from last time 575 00:31:44,800 --> 00:31:46,360 so pull those out. 576 00:31:46,360 --> 00:31:48,830 And then we're going to move on to thermodynamics. 577 00:31:48,830 --> 00:31:52,540 So once we hit thermodynamics, that's exam three material, 578 00:31:52,540 --> 00:31:56,170 so we're almost done with exam two material, a week in advance 579 00:31:56,170 --> 00:31:57,620 to get ready for the exam. 580 00:31:57,620 --> 00:31:58,690 So that's great. 581 00:31:58,690 --> 00:32:02,020 Lots of time to review exam two material 582 00:32:02,020 --> 00:32:06,380 and let's see if we can have an A average on this exam. 583 00:32:06,380 --> 00:32:08,770 That would make me really, really really, happy. 584 00:32:08,770 --> 00:32:13,120 I would wear my periodic table leggings again 585 00:32:13,120 --> 00:32:16,270 if we could get an A average on the exam. 586 00:32:16,270 --> 00:32:19,420 I'm just saying, I'd be very excited. 587 00:32:19,420 --> 00:32:20,800 OK. 588 00:32:20,800 --> 00:32:23,290 So we better finish up that material 589 00:32:23,290 --> 00:32:27,730 so that you can get started, get ready for this. 590 00:32:27,730 --> 00:32:31,810 So we talking about valence bond theory and hybridization 591 00:32:31,810 --> 00:32:34,060 and forming these hybrid orbitals. 592 00:32:34,060 --> 00:32:36,430 And valence bond theory is this idea 593 00:32:36,430 --> 00:32:39,760 that if you have a single electron in an orbital, 594 00:32:39,760 --> 00:32:43,180 it's available to form a bond and bonding happens when 595 00:32:43,180 --> 00:32:46,300 two atoms bring together single electrons 596 00:32:46,300 --> 00:32:49,010 and those pair up to form a bond. 597 00:32:49,010 --> 00:32:51,340 So we talked about electron promotion 598 00:32:51,340 --> 00:32:54,430 before and let's just review what that meant. 599 00:32:54,430 --> 00:32:58,270 So if you have an empty orbital, you 600 00:32:58,270 --> 00:33:00,670 can promote one of your electrons 601 00:33:00,670 --> 00:33:02,620 to that empty orbital. 602 00:33:02,620 --> 00:33:05,470 And so now we have four valence electrons 603 00:33:05,470 --> 00:33:10,450 after electron promotion so that we have more possibility 604 00:33:10,450 --> 00:33:11,800 of forming bonds. 605 00:33:11,800 --> 00:33:14,440 Now if you don't have an empty orbital, 606 00:33:14,440 --> 00:33:16,390 you can't promote your electron. 607 00:33:16,390 --> 00:33:18,250 If you do have an empty orbital, you 608 00:33:18,250 --> 00:33:21,040 can promote it more single electrons 609 00:33:21,040 --> 00:33:22,510 available for bonding. 610 00:33:22,510 --> 00:33:25,150 If you don't have an empty orbital, 611 00:33:25,150 --> 00:33:26,980 there's nothing to do with that. 612 00:33:26,980 --> 00:33:30,591 So that's the trick to electron promotion. 613 00:33:30,591 --> 00:33:31,090 All right. 614 00:33:31,090 --> 00:33:36,340 So now we have one electron in each of the four 615 00:33:36,340 --> 00:33:41,020 valence atomic orbitals that we have for carbon, 616 00:33:41,020 --> 00:33:44,680 but we're going to only hybridize two of them. 617 00:33:44,680 --> 00:33:50,170 We saw already last time that we can hybridize all four orbitals 618 00:33:50,170 --> 00:33:51,670 and have sp 3. 619 00:33:51,670 --> 00:33:55,894 We can hybridize just three of those orbitals and have sp 2. 620 00:33:55,894 --> 00:33:57,310 Now we're going to see that we can 621 00:33:57,310 --> 00:34:00,860 hybridize just two of those orbitals and have sp. 622 00:34:00,860 --> 00:34:02,840 So carbon is really amazing. 623 00:34:02,840 --> 00:34:06,070 It can do all three of these kinds of hybridization. 624 00:34:06,070 --> 00:34:08,560 That's why carbon based life forms 625 00:34:08,560 --> 00:34:11,710 are able to exist and do so much. 626 00:34:11,710 --> 00:34:16,690 So we're going to now hybridize our 2s and our two pz. 627 00:34:16,690 --> 00:34:22,420 Z is just special and so it gets to hybridize 628 00:34:22,420 --> 00:34:27,280 with the 2s leaving two of the other orbitals 629 00:34:27,280 --> 00:34:28,880 just by themselves. 630 00:34:28,880 --> 00:34:31,389 So we're going to form two hybrid orbitals. 631 00:34:31,389 --> 00:34:34,040 Again, if we hybridize two atomic orbitals, 632 00:34:34,040 --> 00:34:37,000 we're going to form two hybrid orbitals. 633 00:34:37,000 --> 00:34:40,270 And if we hybridized 2s and 2pz, we're 634 00:34:40,270 --> 00:34:43,840 going to get hybrid 2sp orbitals. 635 00:34:43,840 --> 00:34:50,831 And we'll have our 2px and our 2py just the same as always. 636 00:34:50,831 --> 00:34:51,330 All right. 637 00:34:51,330 --> 00:34:54,810 So we can think about this in terms of shapes, as well. 638 00:34:54,810 --> 00:34:59,210 So we have, again, our spherically symmetric 639 00:34:59,210 --> 00:35:02,190 s orbitals and our p orbitals and we 640 00:35:02,190 --> 00:35:04,740 have the three of our p orbitals that 641 00:35:04,740 --> 00:35:08,610 are the same shape they just differ in orientation in space. 642 00:35:08,610 --> 00:35:13,640 And so we're just going hybridize our 2pz and our 2s 643 00:35:13,640 --> 00:35:15,810 and so we'll have our kind of funny looking 644 00:35:15,810 --> 00:35:19,530 I think of them as turtle shaped or hybrid orbitals 645 00:35:19,530 --> 00:35:24,930 and then we also have our 2px and 2py orbitals 646 00:35:24,930 --> 00:35:26,640 the same as always. 647 00:35:26,640 --> 00:35:32,120 So what are we going to do with our two sp orbitals and our one 648 00:35:32,120 --> 00:35:35,610 2px and one 2py? 649 00:35:35,610 --> 00:35:39,120 Well, we can form a pretty cool molecule with it. 650 00:35:39,120 --> 00:35:40,860 So we're going to form something that has 651 00:35:40,860 --> 00:35:43,050 a carbon-carbon triple bond. 652 00:35:43,050 --> 00:35:46,140 So this is C2H2. 653 00:35:46,140 --> 00:35:49,680 So now in cyan is the sp orbital, 654 00:35:49,680 --> 00:35:55,800 the hybrid orbital, that is formed on this carbon here. 655 00:35:55,800 --> 00:36:01,590 And then we have a 2px orbital here 656 00:36:01,590 --> 00:36:04,440 in the plane of the screen. 657 00:36:04,440 --> 00:36:10,230 And we have a 2py orbital coming out toward us. 658 00:36:10,230 --> 00:36:12,210 And, of course, our 2pz orbital had 659 00:36:12,210 --> 00:36:14,820 been hybridized with the 2s. 660 00:36:14,820 --> 00:36:18,000 So here we have this structure. 661 00:36:18,000 --> 00:36:21,140 We're going to bring in our other carbon, 662 00:36:21,140 --> 00:36:25,050 and the other carbon has the same situation going on. 663 00:36:25,050 --> 00:36:29,010 And we can form a bond between the two carbons 664 00:36:29,010 --> 00:36:35,220 with our sp orbitals. 665 00:36:35,220 --> 00:36:39,780 And we can form, also, with the sp hybrid orbitals, bonds 666 00:36:39,780 --> 00:36:43,230 to hydrogen. So we have two hydrogens, one over here 667 00:36:43,230 --> 00:36:45,340 and one over there. 668 00:36:45,340 --> 00:36:52,780 So what is the angle between these hydrogens here? 669 00:36:52,780 --> 00:36:53,280 Yeah. 670 00:36:53,280 --> 00:36:58,590 So that's 180 and, again, we have an example 671 00:36:58,590 --> 00:37:00,930 here of the molecule we're going to build that's going 672 00:37:00,930 --> 00:37:02,397 to have a triple bond. 673 00:37:05,290 --> 00:37:11,310 So now let's name those types of bonds 674 00:37:11,310 --> 00:37:13,515 or as sometimes in problem set, it 675 00:37:13,515 --> 00:37:16,830 will say describe the symmetry of the bond. 676 00:37:16,830 --> 00:37:19,680 And what it means by that is the following. 677 00:37:19,680 --> 00:37:22,770 It means that, that's either say name the type of bond 678 00:37:22,770 --> 00:37:24,870 or describe the symmetry. 679 00:37:24,870 --> 00:37:26,640 There's multiple ways to ask the question 680 00:37:26,640 --> 00:37:29,910 and this is the answer to those questions. 681 00:37:29,910 --> 00:37:32,550 So the bond that's formed, the first one that's formed, 682 00:37:32,550 --> 00:37:35,400 between the two carbons is a sigma bond 683 00:37:35,400 --> 00:37:38,400 and it's formed between the sp orbital. 684 00:37:38,400 --> 00:37:39,150 So C2sp, C2sp. 685 00:37:42,330 --> 00:37:43,950 That's the first one. 686 00:37:43,950 --> 00:37:48,310 But this is a triple bond so we have two more bonds to form. 687 00:37:48,310 --> 00:37:54,570 And this is where our atomic px and py orbitals will come in. 688 00:37:54,570 --> 00:37:57,300 So we're going to form the next bond, which is what? 689 00:37:57,300 --> 00:38:00,090 A sigma or pi? 690 00:38:00,090 --> 00:38:05,070 Pi bond and that can be between our x, px, orbitals, 691 00:38:05,070 --> 00:38:08,595 so pi C2px, C2px. 692 00:38:11,490 --> 00:38:16,200 And now, we have the 2py orbitals, as well, 693 00:38:16,200 --> 00:38:19,710 and that allows us to form our triple bond. 694 00:38:19,710 --> 00:38:28,440 So we're also going to have a bond pi C2py, C2py. 695 00:38:28,440 --> 00:38:30,630 So again, with the triple bond, we're 696 00:38:30,630 --> 00:38:34,470 going to have one sigma and two pi bonds. 697 00:38:34,470 --> 00:38:37,910 The sigma is formed from the hybrid orbitals 698 00:38:37,910 --> 00:38:45,810 and the pi bonds are formed by the 2px and 2py orbitals. 699 00:38:45,810 --> 00:38:49,050 So carbon, really impressive. 700 00:38:49,050 --> 00:38:53,460 Carbon can form of these three types of hybrid orbitals. 701 00:38:53,460 --> 00:38:55,860 It can form molecules with single bonds, double bonds, 702 00:38:55,860 --> 00:38:57,176 and triple bonds. 703 00:38:57,176 --> 00:38:58,800 So let's just have a little cheat sheet 704 00:38:58,800 --> 00:39:00,960 to think about that. 705 00:39:00,960 --> 00:39:04,620 So again, this is for carbon hydrocarbon molecules, 706 00:39:04,620 --> 00:39:09,460 like we've looked at so far, that have two carbons in them. 707 00:39:09,460 --> 00:39:15,870 So let's look at carbon in C2H6, so that's over here. 708 00:39:15,870 --> 00:39:19,350 What is going to be the hybridization when 709 00:39:19,350 --> 00:39:23,100 you have a carbon that has a bond to another carbon 710 00:39:23,100 --> 00:39:26,310 and a bond to three hydrogens here? 711 00:39:26,310 --> 00:39:29,550 What hybridization? 712 00:39:29,550 --> 00:39:30,210 sp 3. 713 00:39:30,210 --> 00:39:30,864 That's right. 714 00:39:30,864 --> 00:39:33,030 And it's going to have what kind of a bond-- single, 715 00:39:33,030 --> 00:39:34,351 double, or triple? 716 00:39:34,351 --> 00:39:37,140 It's going to have a single bond and it's 717 00:39:37,140 --> 00:39:39,620 going to have tetrahedral geometry 718 00:39:39,620 --> 00:39:41,514 around both of the carbons. 719 00:39:41,514 --> 00:39:42,930 So both of these carbons are going 720 00:39:42,930 --> 00:39:45,090 to have tetrahedral geometry, which 721 00:39:45,090 --> 00:39:49,320 is not a blank in your note, but what's the angle? 722 00:39:49,320 --> 00:39:52,590 109.5, right. 723 00:39:52,590 --> 00:39:54,410 Thank you. 724 00:39:54,410 --> 00:40:01,417 So we have carbons C2H2 are going to be sp 2 hybridized. 725 00:40:01,417 --> 00:40:03,000 And what kind of a bond are they going 726 00:40:03,000 --> 00:40:05,290 to have between the two carbons? 727 00:40:05,290 --> 00:40:06,840 That will be a double bond. 728 00:40:06,840 --> 00:40:10,190 And what is the geometry of that? 729 00:40:10,190 --> 00:40:10,690 Right. 730 00:40:10,690 --> 00:40:12,270 Trigonal planar. 731 00:40:12,270 --> 00:40:14,740 And here, you have to pretend this is a double bond, 732 00:40:14,740 --> 00:40:17,760 my model kit didn't come with double bond possibilities 733 00:40:17,760 --> 00:40:20,430 and I have to hold it very carefully, 734 00:40:20,430 --> 00:40:26,670 but if I hold it very y-- oh-- the bonds are still there. 735 00:40:26,670 --> 00:40:30,040 You'll see that the angles are 120 736 00:40:30,040 --> 00:40:34,590 and so this is trigonal planar geometry at each carbon. 737 00:40:34,590 --> 00:40:35,880 We didn't tape that one. 738 00:40:35,880 --> 00:40:38,700 You can see there's scotch tape all over the others. 739 00:40:38,700 --> 00:40:40,620 It was not a happy molecule. 740 00:40:40,620 --> 00:40:41,400 OK. 741 00:40:41,400 --> 00:40:46,550 So now, C2H2, what kind of hybridization? 742 00:40:46,550 --> 00:40:50,580 sp, that is our friend the triple bond 743 00:40:50,580 --> 00:40:54,330 and we're going to have linear geometry and 180. 744 00:40:54,330 --> 00:40:58,410 So both carbons have linear geometry. 745 00:40:58,410 --> 00:40:59,620 That works. 746 00:40:59,620 --> 00:41:02,250 It's always triple bonds are much more stable, 747 00:41:02,250 --> 00:41:03,610 they don't fall apart as much. 748 00:41:03,610 --> 00:41:04,110 OK. 749 00:41:04,110 --> 00:41:06,150 So that's a cheat sheet for carbon. 750 00:41:06,150 --> 00:41:09,510 Now if you're thinking about nitrogen or oxygen, 751 00:41:09,510 --> 00:41:11,970 those often have lone pairs on them. 752 00:41:11,970 --> 00:41:14,190 Carbon likes to form all bonds, it 753 00:41:14,190 --> 00:41:16,820 doesn't care double, triple, single, whatever, 754 00:41:16,820 --> 00:41:19,650 but it doesn't really have a lot of lone pairs on it. 755 00:41:19,650 --> 00:41:22,475 But oxygen, nitrogen have lone pairs 756 00:41:22,475 --> 00:41:23,850 and whenever you have lone pairs, 757 00:41:23,850 --> 00:41:26,100 you have to worry about what the geometry is 758 00:41:26,100 --> 00:41:29,190 because the geometry gets named based on the atoms 759 00:41:29,190 --> 00:41:31,480 that you do see, not the lone pairs. 760 00:41:31,480 --> 00:41:35,031 So this cheat sheet works for carbon without lone pairs. 761 00:41:35,031 --> 00:41:37,530 If you have lone pairs, you've got to go back to your vesper 762 00:41:37,530 --> 00:41:40,751 and think about what the names of the geometries are. 763 00:41:40,751 --> 00:41:41,250 OK. 764 00:41:41,250 --> 00:41:43,380 So rules, and I posted this on Steller 765 00:41:43,380 --> 00:41:47,550 for the problem set that was due today, 766 00:41:47,550 --> 00:41:51,750 and so very simple for determining hybridization. 767 00:41:51,750 --> 00:41:54,080 And this is the kind of equation that will not 768 00:41:54,080 --> 00:41:56,530 be on an equation sheet for an exam, 769 00:41:56,530 --> 00:41:57,840 you just need to know that. 770 00:41:57,840 --> 00:42:01,350 So in determining hybridization of an atom 771 00:42:01,350 --> 00:42:03,030 in a complex molecule, you're going 772 00:42:03,030 --> 00:42:06,120 to be thinking about the number of bonded atoms plus the number 773 00:42:06,120 --> 00:42:08,850 of lone pairs is going to be equal to the number 774 00:42:08,850 --> 00:42:11,820 of hybrid orbitals. 775 00:42:11,820 --> 00:42:15,420 So now, clicker question, what is 776 00:42:15,420 --> 00:42:17,340 the hybridization of an atom that has 777 00:42:17,340 --> 00:42:19,700 exactly two hybrid orbitals? 778 00:42:32,610 --> 00:42:33,180 All right. 779 00:42:33,180 --> 00:42:33,861 10 seconds. 780 00:42:48,690 --> 00:42:50,490 Yes. 781 00:42:50,490 --> 00:42:51,070 Right. 782 00:42:51,070 --> 00:42:53,340 sp. 783 00:42:53,340 --> 00:42:56,490 So we can take a look at that two hybrid orbitals are formed 784 00:42:56,490 --> 00:43:00,810 by one at 1s orbital and 1p orbital 785 00:43:00,810 --> 00:43:04,440 and if you have two things bonded and no lone pairs, 786 00:43:04,440 --> 00:43:06,960 that's what you would get. 787 00:43:06,960 --> 00:43:15,930 Three hybrid orbitals would be sp 2 and four would be sp 3. 788 00:43:15,930 --> 00:43:17,760 So again, you're going to just be thinking 789 00:43:17,760 --> 00:43:19,980 in these problems about how many atoms 790 00:43:19,980 --> 00:43:24,030 are bonded to that central atom and how many lone pairs do 791 00:43:24,030 --> 00:43:24,870 you have. 792 00:43:24,870 --> 00:43:27,840 And that's going to then let you figure out 793 00:43:27,840 --> 00:43:29,850 what your hybridization is. 794 00:43:29,850 --> 00:43:32,910 And we have one exception which is 795 00:43:32,910 --> 00:43:36,660 that if an atom has a single bond 796 00:43:36,660 --> 00:43:40,050 and it's terminal on the edge of the molecule, then 797 00:43:40,050 --> 00:43:42,870 we're not going hybridize it. 798 00:43:42,870 --> 00:43:47,680 So we can now take a look at an example of this 799 00:43:47,680 --> 00:43:50,854 and this is going to be another-- yeah, 800 00:43:50,854 --> 00:43:52,020 just keep your clickers out. 801 00:43:52,020 --> 00:43:54,144 We've got a whole bunch of clicker questions coming 802 00:43:54,144 --> 00:43:56,760 at you kind of in a row here. 803 00:43:56,760 --> 00:44:00,750 And if we have this molecule, it has a central carbon 804 00:44:00,750 --> 00:44:03,270 and three terminal atoms. 805 00:44:03,270 --> 00:44:08,910 Now help me figure out what kinds of bonds this will form. 806 00:44:08,910 --> 00:44:12,840 So which one of these has the correct bond 807 00:44:12,840 --> 00:44:14,610 types for this molecule? 808 00:44:34,510 --> 00:44:36,070 All right. 809 00:44:36,070 --> 00:44:37,510 Make a decision. 810 00:44:37,510 --> 00:44:39,200 Let's just take 10 more seconds. 811 00:44:55,960 --> 00:44:56,862 Interesting. 812 00:44:59,510 --> 00:45:03,640 I think some time I re-poll, but I think that we'll just kind 813 00:45:03,640 --> 00:45:11,890 of go over this one and then we'll-- do you want to go ahead 814 00:45:11,890 --> 00:45:14,173 and show the answer and then-- this is-- 815 00:45:14,173 --> 00:45:18,310 AUDIENCE: [SIDE CONVERSATIONS] 816 00:45:18,310 --> 00:45:20,740 CATHERINE DRENNAN: And if it wasn't a clicker competition, 817 00:45:20,740 --> 00:45:22,930 I might have you discuss it more and re-poll, 818 00:45:22,930 --> 00:45:24,140 but it's a competition. 819 00:45:24,140 --> 00:45:25,300 So let's go over it. 820 00:45:25,300 --> 00:45:29,410 So this one isn't in your notes so if you 821 00:45:29,410 --> 00:45:31,720 want to write it at the bottom of the page, 822 00:45:31,720 --> 00:45:33,724 we'll go over what the answer is. 823 00:45:33,724 --> 00:45:35,140 Hopefully there's a typo in there, 824 00:45:35,140 --> 00:45:36,514 but we'll see when we go through. 825 00:45:36,514 --> 00:45:37,660 All right. 826 00:45:37,660 --> 00:45:42,850 So let's take a look at this molecule. 827 00:45:42,850 --> 00:45:45,450 Hydrogen is terminal and single bonded, 828 00:45:45,450 --> 00:45:47,200 but we've already talked about hydrogen 829 00:45:47,200 --> 00:45:48,670 so we kind of knew that. 830 00:45:48,670 --> 00:45:52,810 Oxygen is terminal, but it's double bonded 831 00:45:52,810 --> 00:45:55,180 so we need to hybridize it. 832 00:45:55,180 --> 00:46:02,350 Cl is terminal and single bonded so we don't hybridize this 833 00:46:02,350 --> 00:46:06,040 and we don't hybridize hydrogen, never hybridized hydrogen. OK. 834 00:46:06,040 --> 00:46:08,620 So let's look at the kind of bonds that are formed. 835 00:46:08,620 --> 00:46:16,940 So we have a sigma bond, single bond, this carbon is C2sp 2. 836 00:46:16,940 --> 00:46:19,510 It's bonded to three different things 837 00:46:19,510 --> 00:46:25,220 and it has no lone pairs so that makes it three 838 00:46:25,220 --> 00:46:26,970 that there's three things so we have three 839 00:46:26,970 --> 00:46:30,040 hybrid orbitals, which is sp 2. 840 00:46:30,040 --> 00:46:33,120 Our hydrogen is just 1s, it's always just 1s. 841 00:46:33,120 --> 00:46:35,010 That's all it is. 842 00:46:35,010 --> 00:46:38,310 So let's look at this bond now. 843 00:46:38,310 --> 00:46:43,950 So we have a single bond between our carbon that is 2sp 2 844 00:46:43,950 --> 00:46:47,010 and then, we also have this oxygen. 845 00:46:47,010 --> 00:46:50,460 We do hybridize it because it has a double bond 846 00:46:50,460 --> 00:46:53,220 and it has two sets of lone pairs 847 00:46:53,220 --> 00:46:55,230 and it's bonded to one atom, so it 848 00:46:55,230 --> 00:47:00,570 has three hybrid orbitals, so it's sp 2 just like the carbon. 849 00:47:00,570 --> 00:47:03,270 And then we have a pi bond and the pi bond 850 00:47:03,270 --> 00:47:07,080 is made up of atomic orbitals, either 2px or 2py. 851 00:47:09,990 --> 00:47:13,800 Chlorine is single bonded so we're not 852 00:47:13,800 --> 00:47:17,370 going to hybridize it because it is single bonded 853 00:47:17,370 --> 00:47:18,750 and it's terminal. 854 00:47:18,750 --> 00:47:24,600 So it's a single bond, it's from this carbon that's C2sp 2, 855 00:47:24,600 --> 00:47:29,490 we already saw that, and then the chlorine is 856 00:47:29,490 --> 00:47:35,230 going to be terminal and so it's Cl3pz 857 00:47:35,230 --> 00:47:38,337 and so that's a non-hybridized orbital. 858 00:47:45,020 --> 00:47:48,420 So good practice for the clicker. 859 00:47:48,420 --> 00:47:51,620 I think that one could help, but we're 860 00:47:51,620 --> 00:47:54,110 going to have more practice now. 861 00:47:54,110 --> 00:47:58,134 I threw in a bunch of extra problems so that one was extra 862 00:47:58,134 --> 00:48:00,050 and now, let's do the one that is in the notes 863 00:48:00,050 --> 00:48:04,400 from last time, which is vitamin C. 864 00:48:04,400 --> 00:48:08,990 So I'll give you another minute if everyone has that one down. 865 00:48:08,990 --> 00:48:10,910 OK. 866 00:48:10,910 --> 00:48:16,400 So let's look at vitamin C. So vitamin C 867 00:48:16,400 --> 00:48:21,200 is needed to form collagen in your body. 868 00:48:21,200 --> 00:48:27,930 Without enough vitamin C in your diet, you could be in trouble. 869 00:48:27,930 --> 00:48:30,649 So it doesn't happen too much anymore 870 00:48:30,649 --> 00:48:32,690 because there's vitamin supplements and all sorts 871 00:48:32,690 --> 00:48:37,100 of things, but often, vitamin C deficiency is associated 872 00:48:37,100 --> 00:48:42,050 with sailors who went out to sea and didn't have a healthy diet 873 00:48:42,050 --> 00:48:46,130 and they became deficient in vitamin C and got scurvy. 874 00:48:46,130 --> 00:48:47,867 And so then they had to figure out 875 00:48:47,867 --> 00:48:49,700 they had to eat oranges or other things that 876 00:48:49,700 --> 00:48:54,110 were rich in vitamin C. In terms of who should be concerned 877 00:48:54,110 --> 00:48:59,960 about vitamin C deficiency, us, primates, we don't make vitamin 878 00:48:59,960 --> 00:49:03,050 C, so we have to get it in our diet and also, Guinea pigs. 879 00:49:03,050 --> 00:49:04,290 Most other animals make it. 880 00:49:04,290 --> 00:49:07,280 I don't really know why-- maybe this is why Guinea pigs are 881 00:49:07,280 --> 00:49:10,460 called Guinea pigs, they're good for scurvy experiments 882 00:49:10,460 --> 00:49:14,150 because they don't make vitamin C. All right. 883 00:49:14,150 --> 00:49:17,090 So let's look at this vitamin C molecule 884 00:49:17,090 --> 00:49:19,190 and think about what type of molecule 885 00:49:19,190 --> 00:49:21,560 it is and this is a quicker question. 886 00:49:21,560 --> 00:49:23,810 So we have to remember back more material that's 887 00:49:23,810 --> 00:49:25,730 going to be on exam two. 888 00:49:25,730 --> 00:49:29,300 Does that look like a polar or non-polar molecule 889 00:49:29,300 --> 00:49:32,520 and what's true about polar and non-polar molecules? 890 00:49:47,160 --> 00:49:48,350 All right 10 more seconds. 891 00:50:03,436 --> 00:50:03,936 Great. 892 00:50:08,220 --> 00:50:13,990 So it is polar and it, therefore, water soluble 893 00:50:13,990 --> 00:50:19,200 and so you know that because if there's atoms in there that 894 00:50:19,200 --> 00:50:21,360 have differences of electronegativity 895 00:50:21,360 --> 00:50:25,320 of greater than 0.4, carbon and oxygen of a difference 896 00:50:25,320 --> 00:50:28,020 in electronegativity of greater than 0.4, 897 00:50:28,020 --> 00:50:32,190 oxygen hydrogen also, electronegativity 898 00:50:32,190 --> 00:50:34,200 differences greater than 0.4. 899 00:50:34,200 --> 00:50:36,540 So we have a lot of polar bonds and they're not 900 00:50:36,540 --> 00:50:37,770 canceling each other out. 901 00:50:37,770 --> 00:50:40,260 It's not a symmetric molecule so therefore, it 902 00:50:40,260 --> 00:50:43,480 would be a polar molecule and water soluble. 903 00:50:43,480 --> 00:50:43,980 OK. 904 00:50:43,980 --> 00:50:44,480 Great. 905 00:50:44,480 --> 00:50:48,450 So you're good on your polar covalent bonds which is also 906 00:50:48,450 --> 00:50:49,871 going to be on exam two. 907 00:50:49,871 --> 00:50:50,370 All right. 908 00:50:50,370 --> 00:50:51,920 So let's go back to hybridization 909 00:50:51,920 --> 00:50:53,970 and have a little more practice on that. 910 00:50:53,970 --> 00:50:55,980 So don't put your clickers away. 911 00:50:55,980 --> 00:50:58,470 Why don't you tell me the hybridization 912 00:50:58,470 --> 00:51:04,950 of carbon a labeled up here and in your notes. 913 00:51:12,710 --> 00:51:13,210 All right. 914 00:51:13,210 --> 00:51:14,071 10 more seconds. 915 00:51:28,980 --> 00:51:30,930 All right. 916 00:51:30,930 --> 00:51:33,510 So we know what clicker questions are 917 00:51:33,510 --> 00:51:36,280 going to determine the winners. 918 00:51:36,280 --> 00:51:36,780 OK. 919 00:51:36,780 --> 00:51:41,040 So carbon a was sp 3 hybridized. 920 00:51:41,040 --> 00:51:45,870 So if we look at it over here, it has bonded to four things 921 00:51:45,870 --> 00:51:50,320 so there's four which makes it sp 3. 922 00:51:50,320 --> 00:51:50,820 OK. 923 00:51:50,820 --> 00:51:55,050 So let's just do the rest and you can yell these out. 924 00:51:55,050 --> 00:52:00,956 Carbon labeled b, what kind of hybridization for carbon b? 925 00:52:00,956 --> 00:52:02,255 AUDIENCE: Sp 3. 926 00:52:02,255 --> 00:52:04,860 CATHERINE DRENNAN: Sp 3. 927 00:52:04,860 --> 00:52:06,770 Carbon c? 928 00:52:06,770 --> 00:52:08,510 AUDIENCE: Sp 3. 929 00:52:08,510 --> 00:52:10,100 CATHERINE DRENNAN: Sp 3. 930 00:52:10,100 --> 00:52:12,450 Again, you just want to count how many bonds 931 00:52:12,450 --> 00:52:17,730 you have going on or lone pairs, but carbon doesn't usually 932 00:52:17,730 --> 00:52:18,990 like to have lone pairs. 933 00:52:18,990 --> 00:52:20,430 What about carbon d? 934 00:52:20,430 --> 00:52:21,860 AUDIENCE: sp 2. 935 00:52:21,860 --> 00:52:23,651 CATHERINE DRENNAN: Sp 2. 936 00:52:23,651 --> 00:52:24,150 Right. 937 00:52:24,150 --> 00:52:29,960 It only has-- if we look at that one over here, 938 00:52:29,960 --> 00:52:33,210 I'm supposed to point to this one-- so carbon d over here, 939 00:52:33,210 --> 00:52:37,890 it has three atoms that it's bound to. 940 00:52:37,890 --> 00:52:39,172 Carbon e? 941 00:52:41,944 --> 00:52:48,800 sp 2 and carbon f? 942 00:52:48,800 --> 00:52:49,440 AUDIENCE: sp 2. 943 00:52:49,440 --> 00:52:50,440 CATHERINE DRENNAN: Sp 2. 944 00:52:50,440 --> 00:52:51,810 Right. 945 00:52:51,810 --> 00:52:56,250 So now that we did that, we can use this information 946 00:52:56,250 --> 00:52:58,800 when we think about the bonds that 947 00:52:58,800 --> 00:53:03,850 are formed between these carbons and the other atoms. 948 00:53:03,850 --> 00:53:08,140 So let's look at bonding now. 949 00:53:08,140 --> 00:53:12,480 So if we look at carbon b, two hydrogen, 950 00:53:12,480 --> 00:53:15,720 that's going to be a sigma bond, and you told me 951 00:53:15,720 --> 00:53:19,710 that carbon b was sp 3 so we write that. 952 00:53:19,710 --> 00:53:21,840 So describe the symmetry around the bond, 953 00:53:21,840 --> 00:53:32,530 name the bond, C2sp 3, H1s, we do not hybridize hydrogen. 954 00:53:32,530 --> 00:53:38,790 So now, for the bond between b and a, again, a sigma bond. 955 00:53:38,790 --> 00:53:45,180 We already looked at the fact that carbon b is 2sp 3, 956 00:53:45,180 --> 00:53:48,720 carbon a was the same. 957 00:53:48,720 --> 00:53:55,740 Now if we look at the difference between b and c, b was C2sp 3 958 00:53:55,740 --> 00:53:58,050 and then c is also the same. 959 00:53:58,050 --> 00:53:59,690 Remember to write the twos, remember 960 00:53:59,690 --> 00:54:02,260 to write the hybridization, remember to write the element, 961 00:54:02,260 --> 00:54:05,280 remember to write sigma for the single bond. 962 00:54:05,280 --> 00:54:08,510 Grading these questions on the exam is not fun. 963 00:54:08,510 --> 00:54:11,100 You've got to remember to have all those things in there 964 00:54:11,100 --> 00:54:14,800 so if you get them all in there, it makes everyone very happy. 965 00:54:14,800 --> 00:54:15,300 OK. 966 00:54:15,300 --> 00:54:20,220 Now let's look at carbon b to the oxygen. 967 00:54:20,220 --> 00:54:22,830 It's also a single bond, so sigma. 968 00:54:22,830 --> 00:54:26,730 We know that carbon b is C2sp 3. 969 00:54:26,730 --> 00:54:30,990 The oxygen here is also going to be sp 3 970 00:54:30,990 --> 00:54:35,820 because it has two bonded atoms and two sets of lone pairs. 971 00:54:35,820 --> 00:54:36,390 OK. 972 00:54:36,390 --> 00:54:37,882 One more clicker. 973 00:54:57,421 --> 00:54:57,920 All right. 974 00:54:57,920 --> 00:54:58,827 10 more seconds. 975 00:55:13,440 --> 00:55:14,010 Great. 976 00:55:14,010 --> 00:55:16,130 Yup. 977 00:55:16,130 --> 00:55:20,090 So that is correct and if we take a look at that over here, 978 00:55:20,090 --> 00:55:25,670 we have carbon d, it has bonded to three things so it's sp 2 979 00:55:25,670 --> 00:55:29,430 and the oxygen is bonded to two atoms and two lone pairs 980 00:55:29,430 --> 00:55:32,510 so it's sp 3. 981 00:55:32,510 --> 00:55:37,610 We can keep going and finish up between d and c now, 982 00:55:37,610 --> 00:55:41,810 we have-- oops, sorry, d and c up here, 983 00:55:41,810 --> 00:55:46,790 we have d which is 2sp 2 bonded to three things, 984 00:55:46,790 --> 00:55:52,040 c has bonded to four things, it's C2sp 3. 985 00:55:52,040 --> 00:55:57,800 And then finally, d to e, we have two bonds. 986 00:55:57,800 --> 00:56:02,030 We have a sigma bond so that's between our two-- 987 00:56:02,030 --> 00:56:04,820 these two carbons here are hybridized orbitals 988 00:56:04,820 --> 00:56:08,450 and again, it's 2sp 2, 2sp 2. 989 00:56:08,450 --> 00:56:13,040 And it's a double bond so we have one sigma and one pi bond 990 00:56:13,040 --> 00:56:18,290 and the pi bond is between non-hybridized orbitals, 991 00:56:18,290 --> 00:56:25,160 so it's C2py, C2py or you could have used x, 992 00:56:25,160 --> 00:56:27,270 I don't really care about that. 993 00:56:27,270 --> 00:56:28,070 All right. 994 00:56:28,070 --> 00:56:28,790 Good practice. 995 00:56:28,790 --> 00:56:30,710 I think you're getting the hang of this. 996 00:56:30,710 --> 00:56:33,530 Again, there will be more practice problems 997 00:56:33,530 --> 00:56:38,240 on hybridization posted today to get you ready for the exam 998 00:56:38,240 --> 00:56:40,850 and also to figure out these bonds. 999 00:56:40,850 --> 00:56:42,500 Once you get the hang of this, it's 1000 00:56:42,500 --> 00:56:46,870 really pretty trivial and good points for an exam.