1 00:00:00,120 --> 00:00:02,460 The following content is provided under a Creative 2 00:00:02,460 --> 00:00:03,850 Commons license. 3 00:00:03,850 --> 00:00:06,090 Your support will help MIT OpenCourseWare 4 00:00:06,090 --> 00:00:10,180 continue to offer high-quality educational resources for free. 5 00:00:10,180 --> 00:00:12,720 To make a donation or to view additional materials 6 00:00:12,720 --> 00:00:16,475 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:16,475 --> 00:00:17,100 at ocw.mit.edu. 8 00:00:26,032 --> 00:00:27,240 CATHERINE DRENNAN: All right. 9 00:00:27,240 --> 00:00:31,950 So moving to today's handout, this 10 00:00:31,950 --> 00:00:33,840 is one of my favorite parts of the course. 11 00:00:33,840 --> 00:00:37,500 Honestly, when I first started teaching 5.111, 12 00:00:37,500 --> 00:00:41,430 I said transition metals are rarely covered 13 00:00:41,430 --> 00:00:43,080 in the intro chemistry courses. 14 00:00:43,080 --> 00:00:45,810 Is it really necessary to cover it here? 15 00:00:45,810 --> 00:00:47,940 And I was told it absolutely was. 16 00:00:47,940 --> 00:00:52,110 It's one of the reasons that a 5 on the AP exam 17 00:00:52,110 --> 00:00:54,450 is not good enough, that you have to take the Advanced 18 00:00:54,450 --> 00:00:55,440 Standing exam. 19 00:00:55,440 --> 00:00:57,690 Because the people who teach inorganic chemistry 20 00:00:57,690 --> 00:01:00,750 found that people who placed out of 5.111 21 00:01:00,750 --> 00:01:02,220 didn't do as well in their course 22 00:01:02,220 --> 00:01:04,620 as people who took 5:111 here. 23 00:01:04,620 --> 00:01:06,570 So this is one of the reasons. 24 00:01:06,570 --> 00:01:08,250 And then I started teaching it, and I 25 00:01:08,250 --> 00:01:10,590 realized this is one of the-- even 26 00:01:10,590 --> 00:01:12,200 though people haven't seen it before 27 00:01:12,200 --> 00:01:15,270 and sometimes will get a little scare-- it's actually 28 00:01:15,270 --> 00:01:16,500 one of the most fun units. 29 00:01:16,500 --> 00:01:18,720 So I absolutely love it, and hopefully you 30 00:01:18,720 --> 00:01:19,729 will love it by the end. 31 00:01:19,729 --> 00:01:21,270 People are like, we never covered it. 32 00:01:21,270 --> 00:01:22,270 Why are you covering it? 33 00:01:22,270 --> 00:01:24,090 We're in chapter 16. 34 00:01:24,090 --> 00:01:24,960 It's fun. 35 00:01:24,960 --> 00:01:25,860 OK. 36 00:01:25,860 --> 00:01:31,140 So transition metals, d-block metals, 37 00:01:31,140 --> 00:01:33,330 because they have those d orbitals. 38 00:01:33,330 --> 00:01:36,720 Yes, we're going back to talking about orbitals again. 39 00:01:36,720 --> 00:01:38,280 And they're called transition metals 40 00:01:38,280 --> 00:01:41,760 because you transition from this part of the periodic table 41 00:01:41,760 --> 00:01:43,140 with your, what kind of orbitals? 42 00:01:43,140 --> 00:01:43,895 AUDIENCE: s. 43 00:01:43,895 --> 00:01:44,770 CATHERINE DRENNAN: s. 44 00:01:44,770 --> 00:01:46,950 To this part of your periodic table with your, what kind of 45 00:01:46,950 --> 00:01:47,440 orbitals? 46 00:01:47,440 --> 00:01:47,930 AUDIENCE: p. 47 00:01:47,930 --> 00:01:48,805 CATHERINE DRENNAN: p. 48 00:01:48,805 --> 00:01:51,900 So they are the transition metals, 49 00:01:51,900 --> 00:01:54,720 and they're often really reactive and very cool. 50 00:01:54,720 --> 00:01:57,510 And many of them, since we're on a biological theme, 51 00:01:57,510 --> 00:01:59,850 many of them are super important in biology. 52 00:01:59,850 --> 00:02:02,100 And I have some of these written down in your notes, 53 00:02:02,100 --> 00:02:04,140 but here they are up here. 54 00:02:04,140 --> 00:02:07,980 In the transition metals, you have a lot of metals 55 00:02:07,980 --> 00:02:10,139 that we could not live without. 56 00:02:10,139 --> 00:02:13,650 Iron carries oxygen to our blood, very important, 57 00:02:13,650 --> 00:02:16,020 hemoglobin. 58 00:02:16,020 --> 00:02:17,940 We talked about cobalt just now. 59 00:02:17,940 --> 00:02:20,220 That is the metal in vitamin B12. 60 00:02:20,220 --> 00:02:22,200 So we know why that's important. 61 00:02:22,200 --> 00:02:24,040 We have zinc everywhere. 62 00:02:24,040 --> 00:02:27,210 Nickel's important for bacteria, not so much for us. 63 00:02:27,210 --> 00:02:28,650 But bacteria is important for us, 64 00:02:28,650 --> 00:02:30,690 so therefore nickel's important to us. 65 00:02:30,690 --> 00:02:33,480 So all of these are really important. 66 00:02:33,480 --> 00:02:37,950 Also, this part of the periodic table is a part of the table 67 00:02:37,950 --> 00:02:41,160 that people love that want to make pharmaceuticals or want 68 00:02:41,160 --> 00:02:44,100 to make new kinds of electrodes or batteries 69 00:02:44,100 --> 00:02:46,450 or all sorts of things. 70 00:02:46,450 --> 00:02:49,080 There's a bunch that are used as probes. 71 00:02:49,080 --> 00:02:52,470 We talked about imaging agents, detecting cancer, and all sorts 72 00:02:52,470 --> 00:02:53,970 of different things like that. 73 00:02:53,970 --> 00:02:58,680 Many of these transition metals are used in those probes 74 00:02:58,680 --> 00:03:01,590 and also in pharmaceuticals. 75 00:03:01,590 --> 00:03:04,770 And so this is sort of a very rich part 76 00:03:04,770 --> 00:03:07,740 of the periodic table, where those d orbitals allow 77 00:03:07,740 --> 00:03:09,810 for properties that are incredibly 78 00:03:09,810 --> 00:03:13,410 useful for our health and for doing all sorts of stuff. 79 00:03:13,410 --> 00:03:15,360 So I love this part. 80 00:03:15,360 --> 00:03:19,470 Again, some of the biological-- global cycling of nitrogen. 81 00:03:19,470 --> 00:03:22,110 We talked about nitrogen fixation, that triple bond. 82 00:03:22,110 --> 00:03:24,570 It's really hard to break nitrogen apart, 83 00:03:24,570 --> 00:03:26,130 but bacteria can do it. 84 00:03:26,130 --> 00:03:29,010 It does it using transition metals. 85 00:03:29,010 --> 00:03:31,640 Fixing carbon, hydrogenase, if you 86 00:03:31,640 --> 00:03:34,740 want to make hydrogen fuel cells that are more biological. 87 00:03:34,740 --> 00:03:37,980 Again, biology uses transition metals in this. 88 00:03:37,980 --> 00:03:41,670 Making vitamins, making deoxynucleotides, respiration, 89 00:03:41,670 --> 00:03:45,260 photosynthesis, it's all due to transition metals. 90 00:03:45,260 --> 00:03:45,760 All right. 91 00:03:45,760 --> 00:03:48,000 So we'll start with just one example, 92 00:03:48,000 --> 00:03:50,790 or one of In Our Own Words segment. 93 00:03:50,790 --> 00:03:53,250 And this focuses on nickel, which is something 94 00:03:53,250 --> 00:03:55,410 very important in bacteria. 95 00:03:55,410 --> 00:03:58,890 And this is actually an example from a collaborative project 96 00:03:58,890 --> 00:04:00,780 between my lab and course 6. 97 00:04:00,780 --> 00:04:02,280 And I know a lot of you are thinking 98 00:04:02,280 --> 00:04:04,560 about being course 6 majors, so I 99 00:04:04,560 --> 00:04:07,560 thought I would tell you about some research of Collin 100 00:04:07,560 --> 00:04:09,390 Stultz, a course 6 professor. 101 00:04:09,390 --> 00:04:11,910 So he was doing some computational analysis 102 00:04:11,910 --> 00:04:15,040 on these proteins that we're studying. 103 00:04:15,040 --> 00:04:17,579 So many of you at this point in the semester 104 00:04:17,579 --> 00:04:19,730 probably feel like you might be getting an ulcer. 105 00:04:19,730 --> 00:04:21,579 But unless you have H. pylori in your gut, 106 00:04:21,579 --> 00:04:24,180 you probably are not actually getting an ulcer. 107 00:04:24,180 --> 00:04:26,600 And you just take a little B12, you'll feel a lot better. 108 00:04:26,600 --> 00:04:27,360 OK. 109 00:04:27,360 --> 00:04:27,650 So here's the video. 110 00:04:27,650 --> 00:04:28,316 [VIDEO PLAYBACK] 111 00:04:28,316 --> 00:04:31,740 - My name is Sarah Bowman, and I am a post-doctoral fellow 112 00:04:31,740 --> 00:04:33,240 at MIT. 113 00:04:33,240 --> 00:04:36,930 I am working on studying a protein 114 00:04:36,930 --> 00:04:41,220 from Helicobacter pylori, which is pathogenic bacteria. 115 00:04:41,220 --> 00:04:46,570 Its kind of ecological niche is in mammalian stomachs. 116 00:04:46,570 --> 00:04:50,140 It's actually very difficult to treat using antibiotics, 117 00:04:50,140 --> 00:04:52,480 because a lot of times when you're given 118 00:04:52,480 --> 00:04:55,900 antibiotics they're going to actually be broken apart 119 00:04:55,900 --> 00:04:59,050 by the acidity of the stomach before they actually ever 120 00:04:59,050 --> 00:05:02,980 get to killing the Helicobacter pylori. 121 00:05:02,980 --> 00:05:05,050 Transition metals in biological systems 122 00:05:05,050 --> 00:05:07,120 are actually really important. 123 00:05:07,120 --> 00:05:09,850 They increase the range of reactivity 124 00:05:09,850 --> 00:05:14,020 that proteins and enzymes are able to access. 125 00:05:14,020 --> 00:05:16,180 Nickel is a transition metal. 126 00:05:16,180 --> 00:05:19,000 I mean, it's a transition metal that's actually fairly 127 00:05:19,000 --> 00:05:22,300 rare in biological systems. 128 00:05:22,300 --> 00:05:26,380 So one of the big things that H. pylori uses nickel for 129 00:05:26,380 --> 00:05:29,440 is an enzyme called urease. 130 00:05:29,440 --> 00:05:36,700 Urease requires something like 24 nickel ions, which is a lot. 131 00:05:36,700 --> 00:05:38,680 Urease is one of the proteins that 132 00:05:38,680 --> 00:05:42,730 allows for a lot of buffering capacity of the organism, 133 00:05:42,730 --> 00:05:45,180 of the H. pylori organism. 134 00:05:45,180 --> 00:05:50,170 The stomach pH is very low, so pH 2-something. 135 00:05:50,170 --> 00:05:53,470 And this bacteria has to swim through the stomach 136 00:05:53,470 --> 00:05:54,820 and then colonize it. 137 00:05:54,820 --> 00:05:57,460 And you'd think that the stomach would just break it apart 138 00:05:57,460 --> 00:06:00,700 like it breaks apart your food. 139 00:06:00,700 --> 00:06:05,560 But in fact, the bacteria itself has mechanisms in place 140 00:06:05,560 --> 00:06:07,990 that allow it to create buffers that 141 00:06:07,990 --> 00:06:09,550 allow it to move through the stomach 142 00:06:09,550 --> 00:06:11,839 and live in the stomach. 143 00:06:11,839 --> 00:06:14,380 And one of those enzymes, and it's really important for that, 144 00:06:14,380 --> 00:06:15,015 is urease. 145 00:06:18,040 --> 00:06:21,600 In humans, nickel, as far as we can tell, 146 00:06:21,600 --> 00:06:24,560 is not essential for any enzymes, 147 00:06:24,560 --> 00:06:29,000 whereas in Helicobacter pylori, for instance, nickel 148 00:06:29,000 --> 00:06:31,280 is an essential transition metal. 149 00:06:31,280 --> 00:06:35,750 And so a really intriguing thing to kind of think about 150 00:06:35,750 --> 00:06:42,350 is just whether we could somehow target the nickel requirement 151 00:06:42,350 --> 00:06:46,220 in this organism and in other bacteria that 152 00:06:46,220 --> 00:06:50,660 would allow us to kill these pathogenic bacteria while not 153 00:06:50,660 --> 00:06:55,027 doing anything that would be harmful to humans. 154 00:06:55,027 --> 00:06:55,610 [END PLAYBACK] 155 00:06:55,610 --> 00:06:57,350 CATHERINE DRENNAN: So I like that video 156 00:06:57,350 --> 00:07:02,600 partly because it brings back acid-base and buffers, as well 157 00:07:02,600 --> 00:07:04,760 as talking about transition metals. 158 00:07:04,760 --> 00:07:09,650 And I love the bacteria being attacked by the acid 159 00:07:09,650 --> 00:07:12,080 and then making a buffer and saving itself. 160 00:07:12,080 --> 00:07:12,770 It's awesome. 161 00:07:12,770 --> 00:07:14,780 OK. 162 00:07:14,780 --> 00:07:18,890 So one of the reasons why these transition metals are 163 00:07:18,890 --> 00:07:21,740 so powerful, they can do so many things, 164 00:07:21,740 --> 00:07:24,890 is that they like to form complexes, 165 00:07:24,890 --> 00:07:32,450 and they like to form complexes with small molecules or ions. 166 00:07:32,450 --> 00:07:36,800 And those ions often will have a lone pair of electrons, 167 00:07:36,800 --> 00:07:38,865 and the metal wants that electron density. 168 00:07:38,865 --> 00:07:42,140 It wants the benefit of that lone pair. 169 00:07:42,140 --> 00:07:46,550 So when you have this lone pair, the metal 170 00:07:46,550 --> 00:07:48,380 will come in contact with that lone pair, 171 00:07:48,380 --> 00:07:51,470 and it'll make a very happy, very happy metal. 172 00:07:51,470 --> 00:07:54,230 And we can think about this interaction 173 00:07:54,230 --> 00:07:59,510 here as the donor atoms are called ligands. 174 00:07:59,510 --> 00:08:02,210 And now let's review something we learned before about 175 00:08:02,210 --> 00:08:05,738 whether this is a Lewis acid or a Lewis base then. 176 00:08:18,150 --> 00:08:19,407 OK, 10 more seconds. 177 00:08:35,370 --> 00:08:36,039 That's right. 178 00:08:36,039 --> 00:08:39,940 So it's a Lewis base. 179 00:08:39,940 --> 00:08:42,909 So if we put this up here, donor atoms 180 00:08:42,909 --> 00:08:45,580 are called ligands, which are Lewis bases, 181 00:08:45,580 --> 00:08:48,750 and the Lewis bases donate the lone pair of electrons. 182 00:08:48,750 --> 00:08:51,250 And again, we can think about the definition that we've been 183 00:08:51,250 --> 00:08:55,120 more used to, where a base is taking H . 184 00:08:55,120 --> 00:08:58,570 It's accepting the proton from the acid. 185 00:08:58,570 --> 00:09:01,960 But there, when it's taking H , it's taking H without its 186 00:09:01,960 --> 00:09:02,950 electrons. 187 00:09:02,950 --> 00:09:06,770 So it's actually donating its loan pairs to form a bond. 188 00:09:06,770 --> 00:09:09,770 And then we can think about Lewis acids. 189 00:09:09,770 --> 00:09:13,180 So the acceptor atoms, which are our transition metals, 190 00:09:13,180 --> 00:09:14,320 are Lewis acids. 191 00:09:14,320 --> 00:09:16,150 They accept the lone pair. 192 00:09:16,150 --> 00:09:21,100 And when an acid that has a proton on it loses H , 193 00:09:21,100 --> 00:09:24,160 it is taking the electrons with it, 194 00:09:24,160 --> 00:09:26,560 because H is leaving without its electrons. 195 00:09:26,560 --> 00:09:28,810 So these definitions work, but these are 196 00:09:28,810 --> 00:09:31,430 sort of more broad definitions. 197 00:09:31,430 --> 00:09:33,790 So here, our metals, any of our transition metals, 198 00:09:33,790 --> 00:09:36,370 are going to be our acceptors, our Lewis acids. 199 00:09:36,370 --> 00:09:37,810 And here are a bunch of ligands. 200 00:09:37,810 --> 00:09:38,530 We have water. 201 00:09:38,530 --> 00:09:39,470 We have NH3. 202 00:09:39,470 --> 00:09:40,600 We have CO. 203 00:09:40,600 --> 00:09:41,800 They have lone pairs. 204 00:09:41,800 --> 00:09:43,510 They can be donor atoms. 205 00:09:43,510 --> 00:09:47,290 And the ligands form complexes with the metals. 206 00:09:47,290 --> 00:09:48,960 And the kind of complexes-- they're 207 00:09:48,960 --> 00:09:51,400 often called coordination complexes, 208 00:09:51,400 --> 00:09:55,300 and that's a metal that's surrounded by ligands. 209 00:09:55,300 --> 00:09:58,000 And here's a little example, a metal in the middle, 210 00:09:58,000 --> 00:10:00,520 and it has the ligands around it. 211 00:10:00,520 --> 00:10:03,850 So let's consider this coordination complex now 212 00:10:03,850 --> 00:10:08,410 and think about what this picture is telling us. 213 00:10:08,410 --> 00:10:10,390 So we have our coordination complex. 214 00:10:10,390 --> 00:10:14,770 We have cobalt in the middle, and we have NH3 groups 215 00:10:14,770 --> 00:10:16,750 as our donor ligands. 216 00:10:16,750 --> 00:10:21,810 And here this bracket indicates the overall charge is plus 3. 217 00:10:21,810 --> 00:10:25,750 Again, the transition metal is going to be the Lewis acid. 218 00:10:25,750 --> 00:10:29,680 It's going to be accepting the lone pairs from the Lewis 219 00:10:29,680 --> 00:10:34,250 bases, which are the ligands, or the donor atoms. 220 00:10:34,250 --> 00:10:36,530 Now, we can think about a new term 221 00:10:36,530 --> 00:10:39,440 called "coordination number." 222 00:10:39,440 --> 00:10:41,900 And that's simply the number of ligands 223 00:10:41,900 --> 00:10:44,950 that are bound to the metal. 224 00:10:44,950 --> 00:10:51,960 So a CN number of 6 would indicate six ligands make up 225 00:10:51,960 --> 00:10:54,120 what's called the primary coordination 226 00:10:54,120 --> 00:10:58,350 sphere, which is the things that are bound directly 227 00:10:58,350 --> 00:11:00,340 to the metal. 228 00:11:00,340 --> 00:11:05,250 So CN numbers for transition metals range from 2 to 12, 229 00:11:05,250 --> 00:11:08,970 but 6 is probably the most common. 230 00:11:08,970 --> 00:11:12,340 So before we think about the shapes of these molecules, 231 00:11:12,340 --> 00:11:17,220 let's just look at the notation for this, 232 00:11:17,220 --> 00:11:20,730 so coordination complex notation. 233 00:11:20,730 --> 00:11:24,690 So I would write this structure up here 234 00:11:24,690 --> 00:11:29,970 within brackets-- cobalt bracket NH3. 235 00:11:29,970 --> 00:11:31,820 You have parentheses around NH3. 236 00:11:31,820 --> 00:11:33,530 There's six of those. 237 00:11:33,530 --> 00:11:36,440 Another bracket here with a plus 3 charge, 238 00:11:36,440 --> 00:11:38,850 indicating the charge on everything, 239 00:11:38,850 --> 00:11:40,470 this whole structure. 240 00:11:40,470 --> 00:11:44,400 But often, coordination complexes with a plus charge 241 00:11:44,400 --> 00:11:46,310 will have counterions around. 242 00:11:46,310 --> 00:11:50,420 So there might be, say, three chlorine minus ions around, 243 00:11:50,420 --> 00:11:52,670 and so that could be written like this, 244 00:11:52,670 --> 00:11:54,150 or it could be written like this. 245 00:11:54,150 --> 00:11:57,870 If you see Cl3 outside of those brackets, 246 00:11:57,870 --> 00:12:00,270 it means that they're counterions. 247 00:12:00,270 --> 00:12:03,480 So if I looked at this, I'd say NH3 is within the brackets. 248 00:12:03,480 --> 00:12:06,080 That means it's bound to the cobalt. So that would tell you 249 00:12:06,080 --> 00:12:09,720 there are six things bound to the cobalt. The Cl is outside. 250 00:12:09,720 --> 00:12:11,310 That indicates it's a counterion. 251 00:12:11,310 --> 00:12:12,730 There are three of them. 252 00:12:12,730 --> 00:12:15,630 So there are three counterions, which then tells you 253 00:12:15,630 --> 00:12:18,281 the charge must be plus 3. 254 00:12:18,281 --> 00:12:18,780 All right. 255 00:12:18,780 --> 00:12:20,170 So there is our notation. 256 00:12:23,281 --> 00:12:23,780 All right. 257 00:12:23,780 --> 00:12:28,190 So now we're back to thinking about geometries. 258 00:12:28,190 --> 00:12:30,800 So this is one of the things I love about this part. 259 00:12:30,800 --> 00:12:32,470 I feel like some people in the course 260 00:12:32,470 --> 00:12:34,790 are just like, new topic, new topic. 261 00:12:34,790 --> 00:12:37,005 Oh, man, when is the new material going to end? 262 00:12:37,005 --> 00:12:40,130 Well, you find you get enough into chemistry, 263 00:12:40,130 --> 00:12:43,790 and you start revisiting topics you've already seen before. 264 00:12:43,790 --> 00:12:45,440 So this is great. 265 00:12:45,440 --> 00:12:45,940 All right. 266 00:12:45,940 --> 00:12:49,430 So coordination number 6. 267 00:12:49,430 --> 00:12:51,550 We haven't maybe heard coordination number 6, 268 00:12:51,550 --> 00:12:53,010 but that's pretty easy to remember. 269 00:12:53,010 --> 00:12:54,940 It's the number of atoms bound. 270 00:12:54,940 --> 00:12:57,552 What type of geometry is this? 271 00:13:00,750 --> 00:13:04,241 You can just yell it out. 272 00:13:04,241 --> 00:13:04,740 Right. 273 00:13:04,740 --> 00:13:07,270 So that's octahedral geometry. 274 00:13:07,270 --> 00:13:11,640 Again, the solid triangles coming out 275 00:13:11,640 --> 00:13:13,670 indicate they're coming out at you. 276 00:13:13,670 --> 00:13:17,041 Back dashes are going back, and we have our axial. 277 00:13:17,041 --> 00:13:17,540 All right. 278 00:13:17,540 --> 00:13:23,607 So let's see how well you remember CN 5 structures. 279 00:13:23,607 --> 00:13:25,190 And you can keep this up here, and you 280 00:13:25,190 --> 00:13:28,310 can tell me what the name of those two geometries are. 281 00:13:45,050 --> 00:13:45,970 All right. 282 00:13:45,970 --> 00:13:47,800 Why don't you take 10 more seconds. 283 00:13:47,800 --> 00:13:50,710 And here are our structures in real life down here. 284 00:14:02,450 --> 00:14:04,480 People are just like, I want to put see-saw. 285 00:14:04,480 --> 00:14:05,170 No, no. 286 00:14:08,145 --> 00:14:10,195 That is the parent geometry of see-saw, 287 00:14:10,195 --> 00:14:11,600 but not see-saw itself. 288 00:14:11,600 --> 00:14:12,200 OK. 289 00:14:12,200 --> 00:14:16,440 So we have the trigonal bipyramidal 290 00:14:16,440 --> 00:14:17,790 and the square pyramidal. 291 00:14:17,790 --> 00:14:21,810 So I'm holding up the square pyramidal right now. 292 00:14:21,810 --> 00:14:26,220 And then we have the trigonal, because it's trigonal 293 00:14:26,220 --> 00:14:28,320 along here, bipyramidal. 294 00:14:28,320 --> 00:14:30,620 So it's sort of like one pyramid here, 295 00:14:30,620 --> 00:14:33,380 one pyramid there, so bipyramidal. 296 00:14:33,380 --> 00:14:36,950 And if I took off one and we had a lone pair, 297 00:14:36,950 --> 00:14:41,580 then we would get our friend the see-saw. 298 00:14:41,580 --> 00:14:43,130 OK. 299 00:14:43,130 --> 00:14:46,200 Next we have this. 300 00:14:46,200 --> 00:14:49,020 What's that one called? 301 00:14:49,020 --> 00:14:49,910 AUDIENCE: Square. 302 00:14:49,910 --> 00:14:51,502 CATHERINE DRENNAN: Square-- 303 00:14:51,502 --> 00:14:52,210 AUDIENCE: Planar. 304 00:14:52,210 --> 00:14:55,100 CATHERINE DRENNAN: Planar, yep. 305 00:14:55,100 --> 00:14:58,472 And this one? 306 00:14:58,472 --> 00:14:58,972 Tetrahedral. 307 00:15:02,790 --> 00:15:09,230 And now CN number of 3. 308 00:15:09,230 --> 00:15:10,592 What is this one? 309 00:15:10,592 --> 00:15:12,362 AUDIENCE: Trigonal-- 310 00:15:12,362 --> 00:15:13,820 CATHERINE DRENNAN: Trigonal planar. 311 00:15:13,820 --> 00:15:16,110 It's in a plane kind of, if I hold the bonds 312 00:15:16,110 --> 00:15:20,580 and they don't fall off, and it's kind of trigonal. 313 00:15:20,580 --> 00:15:23,120 And then what about the last one? 314 00:15:23,120 --> 00:15:23,997 AUDIENCE: Linear. 315 00:15:23,997 --> 00:15:25,080 CATHERINE DRENNAN: Linear. 316 00:15:25,080 --> 00:15:25,770 OK. 317 00:15:25,770 --> 00:15:29,350 And let's just run through and think about the angles as well. 318 00:15:29,350 --> 00:15:32,320 With octahedral, what are our angles? 319 00:15:32,320 --> 00:15:33,580 AUDIENCE: 90. 320 00:15:33,580 --> 00:15:34,530 CATHERINE DRENNAN: 90. 321 00:15:34,530 --> 00:15:36,200 Trigonal bipyramidal? 322 00:15:36,200 --> 00:15:38,670 AUDIENCE: 90 and 120. 323 00:15:38,670 --> 00:15:41,100 CATHERINE DRENNAN: 90 and 120, that's right. 324 00:15:41,100 --> 00:15:50,710 So we have one 120 around here, and then the top parts were 90. 325 00:15:50,710 --> 00:15:52,160 OK. 326 00:15:52,160 --> 00:15:55,530 We have the square pyramidal. 327 00:15:55,530 --> 00:15:56,340 90. 328 00:15:56,340 --> 00:15:57,060 Square planar? 329 00:15:57,060 --> 00:15:58,200 AUDIENCE: 90. 330 00:15:58,200 --> 00:15:59,220 CATHERINE DRENNAN: 90. 331 00:15:59,220 --> 00:16:00,090 Tetrahedral? 332 00:16:00,090 --> 00:16:02,412 AUDIENCE: 109.7? 333 00:16:02,412 --> 00:16:04,590 CATHERINE DRENNAN: 109.5. 334 00:16:04,590 --> 00:16:06,465 Give credit for 0.7 too. 335 00:16:06,465 --> 00:16:07,930 That's quite close. 336 00:16:07,930 --> 00:16:08,940 Trigonal planar? 337 00:16:08,940 --> 00:16:09,524 AUDIENCE: 120. 338 00:16:09,524 --> 00:16:10,481 CATHERINE DRENNAN: 120. 339 00:16:10,481 --> 00:16:11,170 And linear? 340 00:16:11,170 --> 00:16:11,820 AUDIENCE: 180. 341 00:16:11,820 --> 00:16:13,260 CATHERINE DRENNAN: 180, right. 342 00:16:13,260 --> 00:16:16,779 So you're going to need to remember these for this unit, 343 00:16:16,779 --> 00:16:19,320 but that's OK because you need to remember them for the final 344 00:16:19,320 --> 00:16:19,820 anyway. 345 00:16:19,820 --> 00:16:22,620 So it gives you a nice review. 346 00:16:22,620 --> 00:16:24,870 All right. 347 00:16:24,870 --> 00:16:27,770 So we got every one. 348 00:16:27,770 --> 00:16:28,940 We got them down. 349 00:16:28,940 --> 00:16:30,300 Can look up your old notes. 350 00:16:30,300 --> 00:16:31,670 Just review. 351 00:16:31,670 --> 00:16:32,730 All right. 352 00:16:32,730 --> 00:16:35,560 So coordination complexes also have another name. 353 00:16:35,560 --> 00:16:37,620 They can be called chelates. 354 00:16:37,620 --> 00:16:40,110 Just another name for coordination complex. 355 00:16:40,110 --> 00:16:42,990 So chelates can be the thing. 356 00:16:42,990 --> 00:16:44,880 But you can also say that the ligand 357 00:16:44,880 --> 00:16:47,310 will chelate as another way of saying 358 00:16:47,310 --> 00:16:50,060 that it will bind to a metal. 359 00:16:50,060 --> 00:16:53,730 And it can bind more than once with one or more sites 360 00:16:53,730 --> 00:16:54,990 of attachment. 361 00:16:54,990 --> 00:16:57,570 And the word "chelate" comes from claws, 362 00:16:57,570 --> 00:16:58,650 and I like that picture. 363 00:16:58,650 --> 00:17:02,300 I feel like, yes, these ligands coming in like claws 364 00:17:02,300 --> 00:17:03,850 and binding that metal. 365 00:17:03,850 --> 00:17:07,230 They're chelating that metal. 366 00:17:07,230 --> 00:17:09,720 So there are different names depending 367 00:17:09,720 --> 00:17:12,960 on how many points of attachment they have. 368 00:17:12,960 --> 00:17:15,960 And we have what's known as monodentate-- 369 00:17:15,960 --> 00:17:18,510 "dent" for dentist or tooth. 370 00:17:18,510 --> 00:17:23,130 So that's one point of attachment. 371 00:17:23,130 --> 00:17:26,819 And I bet that without having seen this material ever 372 00:17:26,819 --> 00:17:29,490 before you can tell me what the rest of these are. 373 00:17:29,490 --> 00:17:31,320 What do you think bidentate means? 374 00:17:31,320 --> 00:17:32,280 AUDIENCE: Two. 375 00:17:32,280 --> 00:17:33,330 CATHERINE DRENNAN: Two. 376 00:17:33,330 --> 00:17:34,350 Tridentate? 377 00:17:34,350 --> 00:17:35,747 AUDIENCE: Three. 378 00:17:35,747 --> 00:17:37,080 CATHERINE DRENNAN: Tetradentate? 379 00:17:37,080 --> 00:17:38,329 AUDIENCE: Four. 380 00:17:38,329 --> 00:17:39,620 CATHERINE DRENNAN: Hexadentate? 381 00:17:39,620 --> 00:17:40,180 AUDIENCE: Six. 382 00:17:40,180 --> 00:17:41,429 CATHERINE DRENNAN: Six, right. 383 00:17:41,429 --> 00:17:42,490 There's not one for five. 384 00:17:42,490 --> 00:17:43,450 But this is good. 385 00:17:43,450 --> 00:17:44,912 So don't lose a point on this. 386 00:17:44,912 --> 00:17:46,620 I feel like sometimes people lose a point 387 00:17:46,620 --> 00:17:47,950 on this on the exam. 388 00:17:47,950 --> 00:17:49,800 You knew it in class before I taught it. 389 00:17:49,800 --> 00:17:51,790 You don't want to like somehow work backwards. 390 00:17:51,790 --> 00:17:54,330 So this is easy points right here. 391 00:17:54,330 --> 00:17:56,190 Just remember on the exam, wait a minute, 392 00:17:56,190 --> 00:17:59,171 maybe I already know this. 393 00:17:59,171 --> 00:17:59,670 All right. 394 00:17:59,670 --> 00:18:03,870 So let's look at some examples of chelating 395 00:18:03,870 --> 00:18:07,560 ligands that bind with multiple points of attachment. 396 00:18:07,560 --> 00:18:09,480 And the first one-- we're kind of on a theme 397 00:18:09,480 --> 00:18:14,020 today-- is vitamin B12 that we're going to look at. 398 00:18:14,020 --> 00:18:17,940 So this is called the corrin ring. 399 00:18:17,940 --> 00:18:21,300 Cobalt is in the middle, and that ring 400 00:18:21,300 --> 00:18:25,050 binds with four points of attachment. 401 00:18:25,050 --> 00:18:29,430 So it is a tetradentate ligand, this corrin ring. 402 00:18:29,430 --> 00:18:31,950 There is also an upper ligand, which 403 00:18:31,950 --> 00:18:35,460 is 5 prime-deoxyadenosine, and a lower ligand that's 404 00:18:35,460 --> 00:18:37,320 called dimethylbenzimidazole. 405 00:18:37,320 --> 00:18:38,850 You don't need to know their names. 406 00:18:38,850 --> 00:18:43,470 Overall, it has six ligands in octahedral geometry. 407 00:18:43,470 --> 00:18:46,920 But the corrin ring is a very nice biological example 408 00:18:46,920 --> 00:18:49,590 of a multidentate ligand. 409 00:18:49,590 --> 00:18:52,050 Heme would be the same. 410 00:18:52,050 --> 00:18:54,780 I thought I would show you this rotating around so you 411 00:18:54,780 --> 00:18:57,780 get a better sense and tell you that this structure 412 00:18:57,780 --> 00:19:01,650 of this vitamin was determined by Dorothy Hodgkin, who 413 00:19:01,650 --> 00:19:04,950 won the Nobel Prize in 1964 for determining 414 00:19:04,950 --> 00:19:07,350 the structure by crystallography and also solving 415 00:19:07,350 --> 00:19:09,990 the structure of penicillin. 416 00:19:09,990 --> 00:19:12,810 This was the most complicated molecule 417 00:19:12,810 --> 00:19:15,450 to be solved by crystallography, and a lot of people 418 00:19:15,450 --> 00:19:17,040 said that technique could never be 419 00:19:17,040 --> 00:19:18,720 used to do something that big. 420 00:19:18,720 --> 00:19:20,760 She showed that they were wrong. 421 00:19:20,760 --> 00:19:24,070 In terms of determining the structure of penicillin, 422 00:19:24,070 --> 00:19:25,860 it was during the war. 423 00:19:25,860 --> 00:19:28,110 And people wanted to make more penicillin, 424 00:19:28,110 --> 00:19:30,270 but they had no idea what the structure was so they 425 00:19:30,270 --> 00:19:31,704 didn't know what to make. 426 00:19:31,704 --> 00:19:33,120 And she figured out the structure. 427 00:19:33,120 --> 00:19:34,536 And it's a weird-looking molecule, 428 00:19:34,536 --> 00:19:37,380 so no one would have guessed it without knowing the structure. 429 00:19:37,380 --> 00:19:41,650 So for her pioneering work in crystallography 430 00:19:41,650 --> 00:19:43,730 she won the Nobel Prize. 431 00:19:43,730 --> 00:19:44,250 All right. 432 00:19:44,250 --> 00:19:49,140 So vitamin B12 is one example of a chelate. 433 00:19:49,140 --> 00:19:52,830 Another that's probably more that you probably hear about 434 00:19:52,830 --> 00:19:54,850 the most-- it's almost synonymous with the word 435 00:19:54,850 --> 00:19:58,480 "chelate"-- is EDTA. 436 00:19:58,480 --> 00:20:01,560 Here is the EDTA molecule, and you 437 00:20:01,560 --> 00:20:05,070 see that it has lots of lone pairs 438 00:20:05,070 --> 00:20:08,910 that are just dying to grab onto a metal. 439 00:20:08,910 --> 00:20:10,010 So we have six. 440 00:20:10,010 --> 00:20:15,120 We have 1, 2, 3, 4, 5, 6, six things 441 00:20:15,120 --> 00:20:19,140 that are capable of chelating that metal. 442 00:20:19,140 --> 00:20:21,990 And so here is what the complex looks like. 443 00:20:21,990 --> 00:20:24,170 So the red oxygen can chelate. 444 00:20:24,170 --> 00:20:26,430 The green oxygen here can chelate, 445 00:20:26,430 --> 00:20:29,835 the nitrogen here in dark blue, the other nitrogen 446 00:20:29,835 --> 00:20:34,530 in dark blue here, light blue oxygen here, and also 447 00:20:34,530 --> 00:20:38,310 the purple oxygen. So now why don't you 448 00:20:38,310 --> 00:20:40,860 tell me what the geometry of this 449 00:20:40,860 --> 00:20:42,560 would be as a clicker question. 450 00:20:53,250 --> 00:20:53,957 You ready? 451 00:20:53,957 --> 00:20:54,582 AUDIENCE: Yeah. 452 00:20:54,582 --> 00:20:54,960 CATHERINE DRENNAN: Yeah. 453 00:20:54,960 --> 00:20:56,210 10 more seconds. 454 00:20:56,210 --> 00:20:57,560 Should be fast hopefully. 455 00:21:09,804 --> 00:21:12,660 Yeah, great, 86%. 456 00:21:12,660 --> 00:21:14,400 It is octahedral. 457 00:21:14,400 --> 00:21:16,800 And sometimes it's a little bit hard to see that, 458 00:21:16,800 --> 00:21:19,690 but I helped you out by drawing those bonds in black 459 00:21:19,690 --> 00:21:21,390 that you needed to look at. 460 00:21:21,390 --> 00:21:25,990 So we have four that are in the plane here, one above 461 00:21:25,990 --> 00:21:28,140 and one below here. 462 00:21:28,140 --> 00:21:30,820 So that is octahedral geometry. 463 00:21:30,820 --> 00:21:33,580 Also, how many points of attachment? 464 00:21:33,580 --> 00:21:35,410 What kind of dentate ligand is this? 465 00:21:37,685 --> 00:21:39,190 It's hexadentate as well. 466 00:21:39,190 --> 00:21:44,361 So it has six points of attachment here. 467 00:21:44,361 --> 00:21:44,860 All right. 468 00:21:44,860 --> 00:21:49,480 So EDTA is a really good metal chelator. 469 00:21:49,480 --> 00:21:53,040 And part of the reason that it is such an awesome metal 470 00:21:53,040 --> 00:21:57,110 chelator is because of entropy. 471 00:21:57,110 --> 00:21:59,100 So we're back to entropy again. 472 00:21:59,100 --> 00:22:04,630 So the binding of EDTA to the metal is entropically favored. 473 00:22:04,630 --> 00:22:07,240 And the reason for this is that metals that are, say, 474 00:22:07,240 --> 00:22:11,500 in your body, like if you happen to eat some lead paint, 475 00:22:11,500 --> 00:22:13,540 and that lead is hanging out. 476 00:22:13,540 --> 00:22:14,800 It's not just by itself. 477 00:22:14,800 --> 00:22:17,640 It's coordinating hopefully just to water and not 478 00:22:17,640 --> 00:22:19,670 to proteins in your body. 479 00:22:19,670 --> 00:22:25,180 But when you take some EDTA to prevent your lead poisoning, 480 00:22:25,180 --> 00:22:27,900 one molecule of EDTA will bind to metal, 481 00:22:27,900 --> 00:22:30,760 and all of these waters are going to be released. 482 00:22:30,760 --> 00:22:34,240 So I have over here some lead with a whole bunch 483 00:22:34,240 --> 00:22:35,935 of little waters. 484 00:22:35,935 --> 00:22:39,650 This is quite an ordered system. 485 00:22:39,650 --> 00:22:45,870 But if I take out all of those waters here, 486 00:22:45,870 --> 00:22:49,220 that's a lot more entropy going on than what we had. 487 00:22:49,220 --> 00:22:52,380 And then you have one chelating ligand here, 488 00:22:52,380 --> 00:22:54,460 and that's a pretty simple system. 489 00:22:54,460 --> 00:22:56,770 So this is ordered. 490 00:22:56,770 --> 00:22:58,300 This is disordered. 491 00:22:58,300 --> 00:23:04,067 So the binding of EDTA, one EDTA releases six water molecules, 492 00:23:04,067 --> 00:23:11,300 and that makes it very favorable to do this. 493 00:23:11,300 --> 00:23:14,230 And because of that, chelating molecules, 494 00:23:14,230 --> 00:23:16,680 or the chelate effect, molecules that are chelates, 495 00:23:16,680 --> 00:23:20,200 like metal bound to EDTA, are unusually stable 496 00:23:20,200 --> 00:23:22,540 because of this favorable entropic effect, 497 00:23:22,540 --> 00:23:24,220 this release of water. 498 00:23:24,220 --> 00:23:27,730 So the release of water, the release of increasing entropy, 499 00:23:27,730 --> 00:23:32,620 drives that metal chelation, and you sequester your metal, 500 00:23:32,620 --> 00:23:36,050 which is really good if you're trying to avoid lead poisoning. 501 00:23:36,050 --> 00:23:40,090 So I think this is a nice example of our friend entropy 502 00:23:40,090 --> 00:23:41,630 driving a reaction. 503 00:23:41,630 --> 00:23:44,350 So a lot of you did really well on the exam talking about 504 00:23:44,350 --> 00:23:47,770 factors of delta H and entropy and when you'd have favorable 505 00:23:47,770 --> 00:23:48,730 delta G's. 506 00:23:48,730 --> 00:23:50,560 Here's another nice example where 507 00:23:50,560 --> 00:23:54,700 the chelate effect explains why metal chelates are so unusually 508 00:23:54,700 --> 00:23:56,200 stable. 509 00:23:56,200 --> 00:23:57,070 All right. 510 00:23:57,070 --> 00:23:58,690 So uses of EDTA. 511 00:23:58,690 --> 00:24:01,300 I already just told you one. 512 00:24:01,300 --> 00:24:05,860 Lead poisoning-- all ambulances have EDTA in case someone 513 00:24:05,860 --> 00:24:08,910 is eating some lead paint. 514 00:24:08,910 --> 00:24:12,820 Another thing that EDTA is used for, which I think is fun, 515 00:24:12,820 --> 00:24:16,030 you should all go check if you buy little packaged goods, 516 00:24:16,030 --> 00:24:18,460 and they have a long list of chemical ingredients. 517 00:24:18,460 --> 00:24:19,600 Look for EDTA. 518 00:24:19,600 --> 00:24:20,680 It's often there. 519 00:24:20,680 --> 00:24:24,790 And it says it's "added for freshness," which means 520 00:24:24,790 --> 00:24:27,120 that bacteria need metals. 521 00:24:27,120 --> 00:24:28,840 You have EDTA. 522 00:24:28,840 --> 00:24:30,600 EDTA sequesters the metals. 523 00:24:30,600 --> 00:24:33,850 The bacteria can't live on the food that you're eating. 524 00:24:33,850 --> 00:24:36,660 So instead of saying, food additive 525 00:24:36,660 --> 00:24:39,870 added to kill the bacteria that were otherwise growing 526 00:24:39,870 --> 00:24:42,220 on your food, they say added for freshness. 527 00:24:42,220 --> 00:24:44,240 And I do think that is an improvement. 528 00:24:44,240 --> 00:24:44,740 All right. 529 00:24:44,740 --> 00:24:47,230 Another thing, we've already talked about the importance 530 00:24:47,230 --> 00:24:49,300 of cleaning bathtubs. 531 00:24:49,300 --> 00:24:52,650 To chelate calcium out of bathtub scum, 532 00:24:52,650 --> 00:24:55,650 you have EDTA or other metal chelates. 533 00:24:55,650 --> 00:25:00,040 And then I have my favorite other example 534 00:25:00,040 --> 00:25:02,950 of the use of EDTA. 535 00:25:02,950 --> 00:25:09,730 This favorite example is in Hollywood, the movie Blade. 536 00:25:09,730 --> 00:25:11,830 How do you kill a vampire? 537 00:25:11,830 --> 00:25:14,033 Vampires drink what? 538 00:25:14,033 --> 00:25:14,840 AUDIENCE: Blood. 539 00:25:14,840 --> 00:25:15,881 CATHERINE DRENNAN: Blood. 540 00:25:15,881 --> 00:25:16,660 Blood has? 541 00:25:16,660 --> 00:25:17,530 AUDIENCE: Iron. 542 00:25:17,530 --> 00:25:19,000 CATHERINE DRENNAN: Iron. 543 00:25:19,000 --> 00:25:20,740 EDTA chelates? 544 00:25:20,740 --> 00:25:21,630 AUDIENCE: Iron. 545 00:25:21,630 --> 00:25:22,950 CATHERINE DRENNAN: Iron. 546 00:25:22,950 --> 00:25:25,330 So you get a little dart, and you 547 00:25:25,330 --> 00:25:27,940 have-- you can kind of see them maybe up here-- they're 548 00:25:27,940 --> 00:25:29,830 filled with liquid. 549 00:25:29,830 --> 00:25:31,750 That's EDTA. 550 00:25:31,750 --> 00:25:37,030 You shoot the vampire with EDTA, and the vampire just 551 00:25:37,030 --> 00:25:39,635 disappears, just kind of turns to sort of dust. 552 00:25:39,635 --> 00:25:41,050 [LAUGHTER] 553 00:25:41,050 --> 00:25:43,720 Because it's like mostly iron, and the iron gets chelated. 554 00:25:43,720 --> 00:25:45,267 But it happens right away. 555 00:25:45,267 --> 00:25:46,600 But anyway, I think that's cool. 556 00:25:46,600 --> 00:25:49,540 Yes, what a good way to kill a vampire. 557 00:25:49,540 --> 00:25:51,310 EDTA, it's brilliant. 558 00:25:51,310 --> 00:25:55,450 Excellent use on Hollywood's part for EDTA. 559 00:25:55,450 --> 00:25:55,950 OK. 560 00:25:55,950 --> 00:25:59,740 Metal chelates, all sorts of potential values 561 00:25:59,740 --> 00:26:01,300 that they have. 562 00:26:01,300 --> 00:26:03,220 OK. 563 00:26:03,220 --> 00:26:06,220 So when we're talking about coordination complexes, 564 00:26:06,220 --> 00:26:09,320 we're talking about geometries. 565 00:26:09,320 --> 00:26:14,260 Sometimes the atoms can be arranged in different ways. 566 00:26:14,260 --> 00:26:18,450 And when you have these geometric isomers, 567 00:26:18,450 --> 00:26:20,490 they can have very different properties. 568 00:26:20,490 --> 00:26:23,560 So just look at an example here. 569 00:26:23,560 --> 00:26:26,340 It's a platinum compound, a platinum compound 570 00:26:26,340 --> 00:26:30,600 who has two NH2 groups and two chlorine groups. 571 00:26:30,600 --> 00:26:33,880 And you could arrange those in two different ways. 572 00:26:33,880 --> 00:26:37,470 You could put the NH3 groups on one side and the chlorine 573 00:26:37,470 --> 00:26:40,230 groups on the other side, and that would be cis. 574 00:26:40,230 --> 00:26:42,520 These are cis to each other. 575 00:26:42,520 --> 00:26:45,210 Or you could put a transconfiguration, where 576 00:26:45,210 --> 00:26:47,430 chlorine is here, and then another chlorine 577 00:26:47,430 --> 00:26:50,070 is trans on the other side. 578 00:26:50,070 --> 00:26:52,080 And the same with this. 579 00:26:52,080 --> 00:26:56,340 So cisplatinum here is a potent anti-cancer drug. 580 00:26:56,340 --> 00:27:01,860 And it has to be cisplatinum because it binds to DNA, 581 00:27:01,860 --> 00:27:05,800 and the two bases of DNA displace these chlorines. 582 00:27:05,800 --> 00:27:08,790 So if they're not on the same side, it can't bind to the DNA. 583 00:27:08,790 --> 00:27:12,840 And so this prevents the cancer cells 584 00:27:12,840 --> 00:27:15,330 from being repaired from damaging agents. 585 00:27:15,330 --> 00:27:18,670 Transplatinum does absolutely nothing that anyone knows. 586 00:27:18,670 --> 00:27:22,020 So it's exactly the same composition, 587 00:27:22,020 --> 00:27:26,370 but because they are different isomers from each other-- 588 00:27:26,370 --> 00:27:31,830 and I have, let's see, ah, over here-- different isomers 589 00:27:31,830 --> 00:27:35,460 of each other-- and so chlorines on the same side, 590 00:27:35,460 --> 00:27:38,880 cis versus the trans-- have completely different 591 00:27:38,880 --> 00:27:40,150 properties. 592 00:27:40,150 --> 00:27:43,440 So cisplatinum got a lot of fame because it cured 593 00:27:43,440 --> 00:27:45,450 Lance Armstrong of cancer. 594 00:27:45,450 --> 00:27:48,390 Lance Armstrong now, of course, is a much more controversial 595 00:27:48,390 --> 00:27:50,880 figure than he was at the time. 596 00:27:50,880 --> 00:27:53,580 But still he created an amazing charity 597 00:27:53,580 --> 00:27:57,840 that hopefully is still doing well despite some of his fall 598 00:27:57,840 --> 00:27:59,280 from fame. 599 00:27:59,280 --> 00:27:59,970 OK. 600 00:27:59,970 --> 00:28:04,470 So another type of isomer are called 601 00:28:04,470 --> 00:28:09,300 optical isomers, also called enantiomers or chiral 602 00:28:09,300 --> 00:28:10,800 molecules. 603 00:28:10,800 --> 00:28:14,690 And these are one, again, you have the same composition, 604 00:28:14,690 --> 00:28:17,520 but they are non-superimposable. 605 00:28:17,520 --> 00:28:20,080 They are, in fact, mirror images of each other. 606 00:28:20,080 --> 00:28:22,020 So if my head was a mirror, these 607 00:28:22,020 --> 00:28:24,460 would be mirror images of each other. 608 00:28:24,460 --> 00:28:27,810 And I could try very hard to superimpose them, 609 00:28:27,810 --> 00:28:30,180 bringing the blue molecules over here, 610 00:28:30,180 --> 00:28:32,820 but then the green and the red don't match. 611 00:28:32,820 --> 00:28:34,230 You can come and try. 612 00:28:34,230 --> 00:28:37,170 These are, in fact, non-superimposable mirror 613 00:28:37,170 --> 00:28:38,910 images from each other. 614 00:28:38,910 --> 00:28:42,540 And sometimes they can have very similar properties. 615 00:28:42,540 --> 00:28:43,200 It depends. 616 00:28:43,200 --> 00:28:45,450 But if you put molecules like that that 617 00:28:45,450 --> 00:28:48,680 are known as chiral, chiral molecules, 618 00:28:48,680 --> 00:28:51,630 i.e. enantiomers-- non-superimposable mirror 619 00:28:51,630 --> 00:28:52,840 images. 620 00:28:52,840 --> 00:28:55,170 The human body is very much of a chiral environment. 621 00:28:55,170 --> 00:28:57,180 You have enzymes designed to bind things 622 00:28:57,180 --> 00:28:58,920 in a particular way. 623 00:28:58,920 --> 00:29:01,950 So they can have very, very different properties. 624 00:29:01,950 --> 00:29:02,610 OK. 625 00:29:02,610 --> 00:29:08,950 So we have to do some d-electron counting before we end today. 626 00:29:08,950 --> 00:29:13,020 And I love this because it's really pretty simple 627 00:29:13,020 --> 00:29:14,940 to count d-electrons. 628 00:29:14,940 --> 00:29:18,390 And so we're going to just take a look at some examples. 629 00:29:18,390 --> 00:29:20,640 And for doing this part, we're going 630 00:29:20,640 --> 00:29:26,430 to start using our friend the periodic table again. 631 00:29:26,430 --> 00:29:30,510 And we need to find oxidation numbers, which we just 632 00:29:30,510 --> 00:29:33,540 talked about in the last unit. 633 00:29:33,540 --> 00:29:37,050 So if we have a coordination complex with cobalt, 634 00:29:37,050 --> 00:29:44,580 and this cobalt has those six NH3 groups and our plus 3 635 00:29:44,580 --> 00:29:47,550 charge-- so this is the complex that we have been talking 636 00:29:47,550 --> 00:29:51,660 about-- let's now figure out what the oxidation 637 00:29:51,660 --> 00:29:53,550 number of this is. 638 00:29:53,550 --> 00:29:59,490 And so this NH3 is neutral, so that's given as a hint. 639 00:29:59,490 --> 00:30:04,350 Many of our ligands are going to be neutral ligands. 640 00:30:04,350 --> 00:30:09,000 So if that is 0, what is the charge on the cobalt? 641 00:30:09,000 --> 00:30:10,350 AUDIENCE: Plus 3. 642 00:30:10,350 --> 00:30:12,240 CATHERINE DRENNAN: Plus 3. 643 00:30:12,240 --> 00:30:17,370 Now we're going to use the rules of d-count. 644 00:30:17,370 --> 00:30:19,560 So we have a d-count. 645 00:30:19,560 --> 00:30:25,060 We need to look up the group number from the periodic table, 646 00:30:25,060 --> 00:30:27,660 which, in this case, is 9. 647 00:30:27,660 --> 00:30:34,770 Then we have minus the oxidation number, so we have 9 minus 3, 648 00:30:34,770 --> 00:30:36,120 or 6. 649 00:30:36,120 --> 00:30:39,900 And so this is a d6 system. 650 00:30:39,900 --> 00:30:44,280 And that is all there is to doing these counts. 651 00:30:44,280 --> 00:30:47,640 So let's just try another one. 652 00:30:47,640 --> 00:30:49,620 So we heard about nickel. 653 00:30:49,620 --> 00:30:51,530 We'll do nickel. 654 00:30:51,530 --> 00:30:56,130 Nickel is coordinated by carbon monoxide, 655 00:30:56,130 --> 00:31:00,150 and there are four of those. 656 00:31:00,150 --> 00:31:04,140 So what is my charge on the nickel going to be, 657 00:31:04,140 --> 00:31:06,420 my oxidation number of the nickel? 658 00:31:06,420 --> 00:31:09,156 So what's my overall charge of this complex? 659 00:31:09,156 --> 00:31:09,870 AUDIENCE: 0. 660 00:31:09,870 --> 00:31:11,700 CATHERINE DRENNAN: 0. 661 00:31:11,700 --> 00:31:15,300 CO is also going to be 0. 662 00:31:15,300 --> 00:31:17,310 There's no charge on CO. 663 00:31:17,310 --> 00:31:20,230 So what is the oxidation number of nickel? 664 00:31:20,230 --> 00:31:20,730 AUDIENCE: 0. 665 00:31:20,730 --> 00:31:22,680 CATHERINE DRENNAN: 0. 666 00:31:22,680 --> 00:31:26,212 So then we can do our d-count. 667 00:31:26,212 --> 00:31:30,316 The d-count, what is the group number for nickel? 668 00:31:30,316 --> 00:31:31,250 AUDIENCE: 10. 669 00:31:31,250 --> 00:31:31,920 CATHERINE DRENNAN: What is it? 670 00:31:31,920 --> 00:31:32,461 AUDIENCE: 10. 671 00:31:32,461 --> 00:31:34,770 CATHERINE DRENNAN: 10. 672 00:31:34,770 --> 00:31:37,680 This is the kind of math that always makes me very happy. 673 00:31:37,680 --> 00:31:41,540 10 minus 0 is 10. 674 00:31:41,540 --> 00:31:46,621 So that is a d10 system. 675 00:31:46,621 --> 00:31:47,120 All right. 676 00:31:47,120 --> 00:31:48,286 We'll do one more over here. 677 00:31:48,286 --> 00:31:50,350 And the next one is a clicker question. 678 00:32:01,080 --> 00:32:24,837 Gives me time to write 679 00:32:24,837 --> 00:32:26,170 AUDIENCE: Whenever you're ready. 680 00:32:26,170 --> 00:32:27,120 We're out of time. 681 00:32:27,120 --> 00:32:27,600 CATHERINE DRENNAN: Yep. 682 00:32:27,600 --> 00:32:28,150 All right. 683 00:32:28,150 --> 00:32:29,730 Let's just do 10 more seconds. 684 00:32:43,760 --> 00:32:45,360 Yep. 685 00:32:45,360 --> 00:32:49,620 So here our overall charge is minus 1. 686 00:32:49,620 --> 00:32:54,310 We have the chlorines are minus 1. 687 00:32:54,310 --> 00:32:56,220 NH3 is 0. 688 00:32:56,220 --> 00:32:58,560 Water is 0. 689 00:32:58,560 --> 00:33:05,040 So this has to be plus 2 because plus 2 minus 3 is minus 1. 690 00:33:05,040 --> 00:33:14,120 We have 9 minus 2 is 7, so it's a d7 system. 691 00:33:14,120 --> 00:33:14,850 All right. 692 00:33:14,850 --> 00:33:18,510 So Wednesday, d orbitals. 693 00:33:18,510 --> 00:33:20,260 I cannot wait. 694 00:33:31,070 --> 00:33:32,060 Yes. 695 00:33:32,060 --> 00:33:33,040 All right, 10 seconds. 696 00:33:50,930 --> 00:33:51,500 OK. 697 00:33:51,500 --> 00:33:56,153 Does someone want to tell me why that's the right answer? 698 00:34:02,225 --> 00:34:02,725 Anybody? 699 00:34:07,570 --> 00:34:13,121 We got a nice dangly thing for your keys or ID. 700 00:34:13,121 --> 00:34:13,621 No? 701 00:34:16,513 --> 00:34:19,600 All right. 702 00:34:19,600 --> 00:34:22,000 So here we're thinking about whether things are better 703 00:34:22,000 --> 00:34:25,780 reducing agents or better oxidizing agents. 704 00:34:25,780 --> 00:34:29,960 And here we're given two different redox potentials-- 705 00:34:29,960 --> 00:34:33,460 minus 600 and minus 300. 706 00:34:33,460 --> 00:34:38,620 So the one that is going to be the lower number 707 00:34:38,620 --> 00:34:41,780 is going to be better at reducing other things. 708 00:34:41,780 --> 00:34:45,340 It wants to be oxidized itself. 709 00:34:45,340 --> 00:34:48,159 And then we can think about whether it's 710 00:34:48,159 --> 00:34:53,320 a favorable process in terms of whether the thing that 711 00:34:53,320 --> 00:34:56,469 likes to reduce is actually doing the reducing. 712 00:34:56,469 --> 00:34:59,271 That's going to make it a spontaneous process. 713 00:34:59,271 --> 00:34:59,770 All right. 714 00:34:59,770 --> 00:35:03,070 So these are the kinds of questions 715 00:35:03,070 --> 00:35:06,550 for the oxidation-reduction unit that we just finished. 716 00:35:06,550 --> 00:35:10,660 And this will be on exam 4, which, amazingly, we just 717 00:35:10,660 --> 00:35:13,150 finished an exam, and there's another one. 718 00:35:13,150 --> 00:35:17,790 So exam 4 is two weeks from today. 719 00:35:17,790 --> 00:35:18,880 All right. 720 00:35:18,880 --> 00:35:21,440 From Friday, sorry, two weeks from Friday. 721 00:35:21,440 --> 00:35:21,940 All right. 722 00:35:21,940 --> 00:35:24,640 So today we're going to continue with this unit on transition 723 00:35:24,640 --> 00:35:25,240 metals. 724 00:35:25,240 --> 00:35:27,970 The next exam is going to have oxidation-reduction 725 00:35:27,970 --> 00:35:30,280 and transition metals and a little bit of kinetics. 726 00:35:30,280 --> 00:35:31,454 Kinetics is our last unit. 727 00:35:31,454 --> 00:35:33,745 So we're getting very close to the end of the semester. 728 00:35:36,380 --> 00:35:38,860 So we're finishing up the handout from last time. 729 00:35:38,860 --> 00:35:41,180 Again, we're back to the periodic table. 730 00:35:41,180 --> 00:35:43,000 We're thinking about transition metals. 731 00:35:43,000 --> 00:35:46,660 We're thinking about that middle part of the periodic table, 732 00:35:46,660 --> 00:35:48,505 and so we're thinking about d orbitals. 733 00:35:52,140 --> 00:35:54,990 So there are five d orbitals. 734 00:35:54,990 --> 00:35:58,317 How many s orbitals are there? 735 00:35:58,317 --> 00:35:58,900 AUDIENCE: One. 736 00:35:58,900 --> 00:35:59,858 CATHERINE DRENNAN: One. 737 00:35:59,858 --> 00:36:01,140 How many p orbitals are there? 738 00:36:01,140 --> 00:36:01,680 AUDIENCE: Three. 739 00:36:01,680 --> 00:36:02,721 CATHERINE DRENNAN: Three. 740 00:36:02,721 --> 00:36:04,649 And so d orbitals have five. 741 00:36:04,649 --> 00:36:06,690 And we're not going to talk about really anything 742 00:36:06,690 --> 00:36:08,340 beyond d orbitals in this class. 743 00:36:08,340 --> 00:36:10,740 And frankly, not very many people do. 744 00:36:10,740 --> 00:36:13,300 But d orbitals are amazing, so we have to fit them in. 745 00:36:13,300 --> 00:36:13,800 All right. 746 00:36:13,800 --> 00:36:15,870 So there are five d orbitals. 747 00:36:15,870 --> 00:36:18,630 And they're up here, and you need 748 00:36:18,630 --> 00:36:20,820 to be able to draw their shapes. 749 00:36:20,820 --> 00:36:25,420 And the bar for drawing the shapes is actually pretty low. 750 00:36:25,420 --> 00:36:28,900 So these are my drawings that I made. 751 00:36:28,900 --> 00:36:32,351 And so you can probably do just about as well. 752 00:36:32,351 --> 00:36:32,850 All right. 753 00:36:32,850 --> 00:36:36,930 So the one that has the most unusual shape 754 00:36:36,930 --> 00:36:40,590 is the dz squared. 755 00:36:40,590 --> 00:36:44,740 And so it has its maximum amplitude along the z-axis. 756 00:36:44,740 --> 00:36:46,980 And for this unit, our z-axis is always 757 00:36:46,980 --> 00:36:49,080 going to be up and down here. 758 00:36:49,080 --> 00:36:53,790 y is in the plane of the screen, and x is coming out toward you 759 00:36:53,790 --> 00:36:55,560 and also going into the screen. 760 00:36:55,560 --> 00:37:00,300 And so dz squared has its maximum amplitude along z, 761 00:37:00,300 --> 00:37:05,610 and it also has a doughnut in the xy-plane. 762 00:37:05,610 --> 00:37:09,180 And so I also brought a little model of this. 763 00:37:09,180 --> 00:37:11,310 So here's dz squared. 764 00:37:11,310 --> 00:37:16,540 We have maximum amplitude along the z-axis, up and down. 765 00:37:16,540 --> 00:37:22,050 And we have our little doughnut in our xy-plane. 766 00:37:22,050 --> 00:37:25,950 So then we have dx squared minus y squared, which 767 00:37:25,950 --> 00:37:31,590 has maximum amplitude along x and along y. 768 00:37:31,590 --> 00:37:35,100 And that would look like this. 769 00:37:35,100 --> 00:37:37,620 So we have our maximum amplitudes 770 00:37:37,620 --> 00:37:39,340 that are right on axis. 771 00:37:39,340 --> 00:37:43,530 So if this is y-axis and x is coming out toward you, 772 00:37:43,530 --> 00:37:46,680 those orbitals are pointing right along 773 00:37:46,680 --> 00:37:49,320 that coordinate frame. 774 00:37:49,320 --> 00:37:52,020 The other three orbitals look a little bit 775 00:37:52,020 --> 00:37:57,120 like dx squared minus y squared, but they're not on-axis. 776 00:37:57,120 --> 00:37:58,170 They're off-axis. 777 00:37:58,170 --> 00:38:00,570 They're in between the axes. 778 00:38:00,570 --> 00:38:03,120 So we have dyz. 779 00:38:03,120 --> 00:38:07,740 It has its maximum amplitude 45 degrees off 780 00:38:07,740 --> 00:38:11,650 of the y and the z-axis. 781 00:38:11,650 --> 00:38:14,490 So if this is z-axis here, there's 782 00:38:14,490 --> 00:38:16,840 no maximum amplitude along here. 783 00:38:16,840 --> 00:38:18,300 It's 45 degrees off. 784 00:38:18,300 --> 00:38:24,540 So it's right in the middle between the z and the y. 785 00:38:24,540 --> 00:38:33,870 So dxz has its maximum amplitude 45 degrees between x and z. 786 00:38:33,870 --> 00:38:37,110 So that would be pointing the other way. 787 00:38:37,110 --> 00:38:39,990 And so I tried to draw this keeping 788 00:38:39,990 --> 00:38:42,330 the reference frame the same. 789 00:38:42,330 --> 00:38:44,040 It's a little hard to see the orbitals, 790 00:38:44,040 --> 00:38:45,570 but it would be kind of this. 791 00:38:45,570 --> 00:38:48,690 So we rotate that around, and so that's 792 00:38:48,690 --> 00:38:50,220 what that would look like. 793 00:38:50,220 --> 00:38:56,340 And then dxy we have maximum amplitude 45 degrees in 794 00:38:56,340 --> 00:38:59,880 between the x and the y. 795 00:38:59,880 --> 00:39:02,790 So x coming out, y in the plane. 796 00:39:02,790 --> 00:39:05,100 And so this is, again, a little bit hard to draw. 797 00:39:05,100 --> 00:39:07,530 If I drew it absolutely perfectly and not tilted 798 00:39:07,530 --> 00:39:09,630 at all, you kind of wouldn't see anything. 799 00:39:09,630 --> 00:39:12,130 But that's what that would look like. 800 00:39:12,130 --> 00:39:14,130 So again, the names of this, it tells you 801 00:39:14,130 --> 00:39:17,910 about the relationship between that orbital, 802 00:39:17,910 --> 00:39:23,730 that maximum amplitude, and the axis that we have defined. 803 00:39:23,730 --> 00:39:27,510 So this is very important to know 804 00:39:27,510 --> 00:39:30,660 that these guys are in between the axes, right 805 00:39:30,660 --> 00:39:32,430 in the middle, 45 degrees. 806 00:39:32,430 --> 00:39:36,150 And you'll see why in a few minutes why that's important. 807 00:39:36,150 --> 00:39:36,840 OK. 808 00:39:36,840 --> 00:39:41,670 So just to practice, here are some slightly better pictures 809 00:39:41,670 --> 00:39:42,960 of the orbitals. 810 00:39:42,960 --> 00:39:48,010 And this is the coordinate frame over here, 811 00:39:48,010 --> 00:39:50,800 and now we have the orbitals inside that. 812 00:39:50,800 --> 00:39:55,680 So again, z is going up, y is in the plane of the screen, 813 00:39:55,680 --> 00:39:58,860 and x is going back and also coming out toward us. 814 00:39:58,860 --> 00:40:01,540 So which is this d orbital? 815 00:40:01,540 --> 00:40:03,006 You can just yell it out. 816 00:40:03,006 --> 00:40:03,880 AUDIENCE: dz squared. 817 00:40:03,880 --> 00:40:04,796 CATHERINE DRENNAN: dz. 818 00:40:04,796 --> 00:40:06,360 Yeah, that's easy to remember. 819 00:40:06,360 --> 00:40:09,120 That's the unique-looking one. 820 00:40:09,120 --> 00:40:11,430 What about this one? 821 00:40:11,430 --> 00:40:13,110 First think about the plane. 822 00:40:13,110 --> 00:40:15,300 So it's the xy-plane. 823 00:40:15,300 --> 00:40:17,160 And then, is it on or off-axis? 824 00:40:17,160 --> 00:40:18,166 So which one is this? 825 00:40:18,166 --> 00:40:19,311 AUDIENCE: [INAUDIBLE] 826 00:40:19,311 --> 00:40:20,310 CATHERINE DRENNAN: Yeah. 827 00:40:20,310 --> 00:40:21,750 So this one is on-axis. 828 00:40:21,750 --> 00:40:23,940 You can see the maximum amplitude 829 00:40:23,940 --> 00:40:26,810 of the orbital pointing right along those axes. 830 00:40:26,810 --> 00:40:31,170 So it's right in the corners of that square there. 831 00:40:31,170 --> 00:40:33,515 And then what about this one down here? 832 00:40:33,515 --> 00:40:34,390 AUDIENCE: [INAUDIBLE] 833 00:40:34,390 --> 00:40:35,550 CATHERINE DRENNAN: Yep. 834 00:40:35,550 --> 00:40:37,230 So that would be dxy. 835 00:40:37,230 --> 00:40:41,605 So it's in the xy-plane, but it's 45 degrees off the axes. 836 00:40:41,605 --> 00:40:44,730 So it's in between the axes here. 837 00:40:44,730 --> 00:40:46,222 And what about that one? 838 00:40:46,222 --> 00:40:47,699 AUDIENCE: . 839 00:40:47,699 --> 00:40:48,740 CATHERINE DRENNAN: Right. 840 00:40:48,740 --> 00:40:55,260 So it's along both z and y here. 841 00:40:55,260 --> 00:40:57,240 And then this last one, which is drawn 842 00:40:57,240 --> 00:41:01,770 to kind of come out toward you, so that is along x as well. 843 00:41:01,770 --> 00:41:05,754 So that's dxz, and it's going up along z. 844 00:41:05,754 --> 00:41:07,920 So you can look at the coordinate frame, which we'll 845 00:41:07,920 --> 00:41:11,610 try to keep consistent, and ask yourself, 846 00:41:11,610 --> 00:41:14,700 is it on-axis or off-axis, and which plane is it in? 847 00:41:14,700 --> 00:41:19,230 And that will allow you to name them and also to draw them. 848 00:41:19,230 --> 00:41:23,180 So just to kind of give you more of a three-dimensional sense, 849 00:41:23,180 --> 00:41:26,420 there's these little movies that I'll show you now. 850 00:41:26,420 --> 00:41:29,581 And so you can get a better sense of that awesome doughnut. 851 00:41:29,581 --> 00:41:30,830 It's going to make you hungry. 852 00:41:30,830 --> 00:41:34,410 They even colored it like a really nice original doughnut 853 00:41:34,410 --> 00:41:36,090 that you would get at Dunkin' Donuts. 854 00:41:36,090 --> 00:41:42,240 So the doughnut is in the xy-plane, 855 00:41:42,240 --> 00:41:47,220 and these other lobes are along z. 856 00:41:47,220 --> 00:41:51,570 So now we have dx squared minus y squared, 857 00:41:51,570 --> 00:41:54,900 and you can see that the maximum amplitudes, again, 858 00:41:54,900 --> 00:41:56,350 are along the axes. 859 00:41:56,350 --> 00:41:59,910 Key-- they're along the axes here. 860 00:41:59,910 --> 00:42:01,650 I don't know why it comes out towards you 861 00:42:01,650 --> 00:42:03,720 and-- I didn't, yeah. 862 00:42:03,720 --> 00:42:06,810 But it gives you a good three-dimensional sense 863 00:42:06,810 --> 00:42:07,991 of this. 864 00:42:07,991 --> 00:42:08,490 All right. 865 00:42:08,490 --> 00:42:13,470 So dxy now, again, in the xy-plane. 866 00:42:13,470 --> 00:42:16,920 But instead of being on-axis, it's 45 degrees off-axis. 867 00:42:16,920 --> 00:42:19,750 So you can see, I think, in this really nicely, 868 00:42:19,750 --> 00:42:23,610 it's right between the axes, but it's not touching them. 869 00:42:23,610 --> 00:42:26,232 The axes sort of separate these orbitals. 870 00:42:28,830 --> 00:42:33,000 And then we have xz. 871 00:42:33,000 --> 00:42:37,380 So now we're going up along the z-axis and in the x-plane. 872 00:42:37,380 --> 00:42:44,730 And here it comes at you again, 45 degrees in between z and x. 873 00:42:44,730 --> 00:42:51,850 And then our last one, we have yz. 874 00:42:54,380 --> 00:42:57,230 So the shapes of those later three, 875 00:42:57,230 --> 00:42:59,780 actually even four of them, are the same. 876 00:42:59,780 --> 00:43:01,910 It's just a matter if they're on or off-axis 877 00:43:01,910 --> 00:43:03,620 and which plane they're in. 878 00:43:03,620 --> 00:43:06,211 So this is not too hard to draw. 879 00:43:06,211 --> 00:43:06,710 All right. 880 00:43:06,710 --> 00:43:08,460 So why is this important? 881 00:43:08,460 --> 00:43:13,220 Why should we care exactly how the orbitals are oriented? 882 00:43:13,220 --> 00:43:15,860 And the reason that you should care about that 883 00:43:15,860 --> 00:43:19,550 is because it can explain a lot of the special properties 884 00:43:19,550 --> 00:43:21,760 of transition metals.