What did you learn? >> Alright, good afternoon. Happy May. Everybody may means we're just about done the semester, maybe that spring. And sometimes that means people study is go blissfully astray. This thought for the day comes from the libretto and a famous musical. Anybody know which musical? Off him? If not, that's okay. >> And look up Camelot sometime it comes from that where we were last time was in talking about the chemistry of metals. >> A lot of this is discussed in section 23 in your textbook under the title of metallurgy and the chemistry of metals. A little bit of what we were talking about last time and we'll see some more examples of it today, is also discussed in Section 22. We were talking before about the fact that transition metals can form coordinate covalent bonds with various ligands. Coordination chemistry is all about that aspect of transition metal chemistry. You'll see plenty of other examples of it in Chapter 22 if you take a look there. But what I want to try to do today is come as close as we can to finishing up our discussion of the metals. You don't finish today, we'll finish on Wednesday. And with any luck, we'll see if we can have your exams back for you on Wednesday as well, but we'll see how that goes. Where we had left off was about the middle of the periodic table. >> So we'll resume by talking about group a, B. >> Now just see if I have this in the, in the textbook. >> Yeah. Okay. >> If you look at the periodic table, it's on the inside front cover your textbook, group eight. Bi traditionally encompasses the nine elements that are part of groups 8910 in the more modern numbering of the periodic table. >> So it includes all the elements that you see here. >> And probably the most famous and the most commonplace is iron. Iron is the most abundant metal on Earth. It constitutes essentially all of the Earth's core. About 5% of the Earth's crust as well. Iron ore is called hematite. And basically the way we get elemental iron from hematite, whose formula is if B2O3, it's basically iron three oxide, is to reduce the hematite using carbon. And I think they have some pictures of this sort of thing in your textbook. Section 23.2 shows you a diagram. And actually I have a somewhat better version on a slide. So let me just get that out to the metallurgy of iron. So let's look at this picture for a moment. This is a picture of an iron blast furnace. And you want to get an idea of how big this thing is. Check out the size of the person wearing the lab coat standing here at the bottom of the slide. These things are tall. Basically what happens is iron ore, along with limestone and carpet in the form of Coke, goes in the top. The heat sources down at the bottom, as you can see, as you go closer to the bottom, the temperatures increased dramatically. And the point is what happens there is that the Coke becomes oxidized to any of the various oxides of carbon, but that means that it's taking oxygen away from the iron. So what comes out the bottom of the blast furnace is molten iron, which is about 96% pure iron. The other 4% is leftover carbon from the reduction process. >> And to get rid of that excess carbon, what's done is to blast the molten iron that comes out with oxygen. >> The oxygen oxidizes or the carbon, but not the iron that's left behind. But this is what has to be done to make this essentially 99 plus percent pure iron, which is useful for making things like steel I ends all over the place. >> It's in steel. >> It's in your bloodstream. We've talked about hemoglobin, which contains iron useful for oxygen transport. Your brain, the weather being as nice as it is. I don't see too many people wearing blue jeans today, but a few. So some of you are actually wearing a rather interesting compound of iron. >> This material called Prussian blue is the blue dye that's used in blue jeans, blueprints, things like that. >> What I find most interesting about it from the point of view of being a chemist. >> This contains iron into different oxidation states. >> The iron that forms the complex IND hexa cyan ferrite. >> I am given in brackets. >> Here is iron in the plus two oxidation state, but outside the brackets, we also have iron ions and the plus three oxidation state. So it is possible for iron and other transition metals to occupy more than one oxidation state in the same compound. Other interesting elements here include osmium, which has the highest density of any element, 22.5 grams per milliliter. It's added to other metals in the form of alloys that are harder than usual. Sing IDA make metals harder. You can add some osmium. And those of you who go on to take a course in organic chemistry, you'll find out about the utility of osmium tetroxide as an oxidizing agent. There are many interesting colors of cobalt. >> Probably the one that is most familiar is the color called cobalt blue that is commonly used in fabrics. >> Let me just see if I can find some other examples of some closer cobalt compounds in your textbook. >> I think they had a picture. These are eight, for example, bottom of page 995, a few examples of different colored cobalt compounds, all based on different ligands being attached to the cobalt from a nutrition point of view, will open the door to this discussion. >> We might say more about what these compounds actually looked like a little bit later on in the course. But I'm sure you recognize compounds such as chlorophyll, hemoglobin, vitamin B12. Vitamin B12 is also called cyanotic cobol amine because it contains cobalt. What all of these have in common? So they fall into a class of compounds called Mattel little porphyrin. Now here's what that means is we kind of give you a vague idea of what all of this was about. We were talking about hemoglobin before. But to give you the bigger picture here, this big thing that I've drawn up here takes a little bit of a practice die to take a look at. But one thing you'll find out when we start talking more about organic chemistry a little bit later on, organic chemists just draw pictures like that. Don't bother to pencil in the carbon atoms that are at the corner of each of these vertices that appear this particular kinda drawing. So realize that every place two or more lines come together, they're supposed to be a carbon atom there. But the point is, this cyclic carbon framework basically holds this set of nitrogen atoms that are shown here, that makes the so-called basic porphyrin structure. Now the point is the nitrogen atoms each have a lone pair on them. And it turns out that this little pocket in the middle of this big molecule, it's just the right size to fit a metal atom, which can then make coordinate covalent bonds using those lone pairs on the nitrogen atoms. So without the mental Adam, it's just called a porphyrin. But with the metal atom it's called a Mattel little porphyrin. And the point is, there's a number of everyday compounds that fall into this category. If the metal atom in the middle is a magnesium atom, that's chlorophyll found in plants. Metal atom in the middle is an iron atom that's called hemoglobin, found in people in your bloodstream if the metal atom in the middle is cobol. Okay? Vitamin B12, pretty important for human nutrition. People who suffer from vitamin B12 deficiency have that condition known as pernicious anemia, which we talked about earlier this semester. By the way, if you look at the chapter on coordination chemistry, you may encounter the term poly dentate talking about particular ligands. We mentioned before that all something really needs to be a ligand is to have one lone pair that it can use to attach to something else. But things that have more than one lone pair that they can attach to other metal atoms with are referred to as poly Dent de ligands. And as you can see, this great big molecule here with several nitrogen atoms, each of which can form a covalent bond like that qualifies as something that would have more than one possibility, or the possibility of forming more than one bond to a metal atom. That's what we mean by a poly dentate ligand. So the point is, there's a number of common substances that fall into this category. And most of the time, the metal atom in question is a transition metal. Iridium also makes very colorful compounds. The name Iridium comes from the Latin word for iris, which means colorful sorts of things, rainbow types of phenomena. Iridium is right next to ask me, I'm on the periodic table. We said a moment ago, osmium has a very high density. No surprise, Iridium does. >> Also. >> Nickel is used to make nickles. No surprise there. Nickels are not pure nickel. Other about 20% nickel. Nickel is also fat in stainless steel and in night probe wire, which is used for all kinds of applications, it's called Night Chrome because it's an alloy of nickel and chromium. Now my lecture notes, as I mentioned before, are older than you are. And there is passing mentioned a palladium as a metal that is commonly used in jewelry. However, these days here at the University of Delaware, I would be remiss if I didn't say a little bit more about palladium chemistry, them that. So I'll just point out one thing. And some of you may have already seen this in your travels across campus. >> I'm sure many people have seen it and just kind of ignored it back. >> Suppose a compound like this in which there is some halogen atom like bromine, chlorine, Arieti attached to a carbon, carbon double bond. And let's suppose we have another compound, and I'll just draw a structure that looks something like this. Will worry about it later on also having an x. >> Well, it turns out if I mix these together with palladium, basically what happens is I can link those two pieces together and in the process, form a carbon-carbon bond. >> And it turns out for reasons that will become more clear to those of you who go out and take a course in organic chemistry, that being able to do this is actually a pretty important thing to be able to do. Because what it allows us to do is assemble larger, more interesting, hopefully more biologically active organic molecules from smaller, more boring, less biologically useful organic molecules. The significance of this for the University of Delaware >> Is it? >> This is fundamentally an example of what's called the heck reaction. Professor Richard heck was a faculty member here at the OD for number of years. And this was some of the chemistry that he worked on. And this was some of the chemistry that helped win him and two other scientists the 2010, that Nobel Prize in chemistry. If you've ever walked past a Mentor circle, it seem that great big marble book that's out there. What's written in the book is the heck reaction. Don't notice that. >> But that book is up there as a commemorative to Dr. x research success. >> And the faculty was awarded the Nobel Prize in chemistry for this work. So palladium chemistry is more than just jewelry. And you can see other examples of a kind of a great big book on Mentor circle. Nicole palladium, and platinum are all used as hydrogenation catalysts. We talked about hydrogenation before. It's the technique that is used to convert liquid oils into solid, more saturated fats. And here's an interesting application. Some of the coordination chemistry you had talked about before. >> Consider these two compounds. >> They are the same in terms of what their formula was, are they both consist of platinum atom in the center, two ammonia molecules, two chloride ions both stuck to the platinum atom. >> So a total of four things attach there. >> The only difference between these two molecules is the three-dimensional arrangement of the atoms in space. Notice for example, that in this molecule, the angle between the two platinum chlorine bonds is a 90 degree angle. Here it's more like a 180 degree angle. This is referred to as the cis isomer of this molecule. This is referred to as the trans isomer of this molecule. But the point is that since these two molecules differ only in the arrangement of their atoms in three-dimensional space, they are referred to as stereo isomers of each other. Stereo means shape. Iso means same, same formula, different shapes. And it turns out that this kind of thing could have a very significant impact on the biological behavior of molecules like this. The cis version of this compound, commonly known as cisplatin, turns out to be a very useful compound. And derivatives of it are also very useful in the treatment of certain kinds of cancer. >> By contrast, the trans compound does nothing as far as cancer is concerned. >> So it turns out that having the right formula helps. But having the right formula and also the right geometry can be crucial depending on what you want to actually use the molecule for it. >> Alright, let's move on to the fun group, group 1B. >> Everybody knows about group 1B. >> Copper, silver, gold, right? >> Everybody would trade all the other metals for D equivalent weight of copper, silver, and gold. Copper is obtained from its four by two metallurgical processes called roasting and smelting. Copper occurs in nature as it's sulfide, or the process known as roasting involves heating the sulfide to high temperatures in the presence of oxygen. >> The oxygen does two things. >> It oxidizes sulfur to sulfur dioxide, which is a gas, and also replaces sulfur in the Copper end of the compound with an oxygen atom, which should make sense because oxygen and sulfur in the same group, so they should behave similarly. Then as we showed with the iron, the copper can be smelted by adding carbon in the form of Coke. Heated to high temperatures, the carbon removes the oxygen in the form of CO2 and reduces the copper to its elemental metallic form. Copper is all over the place. We use copper wires for the wiring and people's houses. Copper is the second best conductor of electricity. Brass is an alloy of zinc and copper. Bronze is an alloy of zinc and copper with a little bit of tin thrown in pennies or bronze. Normally, when we look at a penny, we think, OK, and that's basically the color of copper. Well, fundamentally it is, but there's a couple of other metals in there as well. Silver actually turns out to be the best conductor of electricity, as I mentioned before, but it's expensive. So we lead copper wire do the job. >> And people's houses. >> We talked earlier about how you can put a coating of silver on stainless steel silverware. Silver is used in jewelry, of course, and in coinage. And various silver salts, like silver chloride, silver iodide turned out to be useful in black and white photography in lab. When you are making silver chloride, you may have noticed that it came out as a white powder when you first made it. But if you let it stand for a few minutes in the light, it starts to turn kind of a dull gray. That's called photo reduction, in which the silver ions are converted back to silver metal and give the white silver chloride powder a kind of a grayish cast, which actually turns out to be useful in black and white photography. Gold, of course, all kinds of jewelry. >> And there are certain doled compounds that turn out to be effective in treatments of arthritis. >> Now it shouldn't surprise anybody that the cost of those compounds is rather exorbitant. Because let's face it, if you're going to make something out of gold, it's gotta be expensive. Occasionally, there are good reasons, other than market greed, for why the drugs cost as much as they do. >> In group two b. We've seen some of these before, zinc, cadmium, and mercury. >> Mercury is probably the most familiar, but also the most dangerous. Zinc is used that a lot of different ways. >> We've seen before that zinc has a good reducing agent. >> Again, those of you going onto an organic chemistry course, we'll see some more specific examples of that. We've seen zinc used in batteries and also it's used in coinage. Certain zinc compounds like zinc oxide. Zinc oxide was in some of the sunscreen that I was using on Saturday when I day and took in some of the festivities there. The virtue of zinc oxide is at, it's pretty much pure white and a very good absorber of ultraviolet radiation. So zinc oxide based sunscreen should be pretty effective. Zinc sulfide is an example of what's referred to as a phosphor, which means it blows when charged particles strike it. That makes it useful in TV screens, computer monitor screens, things of that nature. Cadmium, that we mentioned earlier, turns out to be a good absorber of neutrons that makes it useful in the control rods are used to control the rates at which nuclear reactions take place in nuclear power plants. And then pretty much anything I say about what Mercury is used for is now obsolete. From the lecture notes. We know that mercury is the only metal that happens to be a liquid under normal circumstances. It was used routinely for a lot of different things. But in recent years, people have decided, hey, you know what? It's probably not a good idea to be putting large amounts of a heavy metal like mercury into people's bodies. So wanted was for a long time use what are called mercury arc lamps for street lights at amalgam is which for a long time we're used in dentistry to make things like silver medal softer and get it into the little spaces in your teeth where it needed to be. Materials have since been developed for those purposes that don't involve the use of mercury. So these days, people's use of Mercury is extremely limited. Like I may have mentioned before when I was a kid. You can very easily pick up a chemistry set that add mercury compounds in it. There's no earthly way you could do that anymore. >> In groups. 3a, by far the most important player is aluminum. >> Let me show you a picture. Ok. There was a time when aluminum was treated as a precious metal, much as we do with silver and gold these days. Then, about a 100 years ago, a young man by the name of Charles Martin Hall, who at the time was an undergraduate student at Oberlin College in Ohio, figured out an easy way to produce aluminum. >> From its ores. The two main ors of aluminum are bauxite, which is aluminum oxide, and cryo light, which is sodium aluminum fluoride. >> And it turns out that if you heat up cryo I till it melts, then dissolve the bauxite in it and run a current of electricity through IT. >> Molten aluminum comes out the bottom. >> So haul found a way to make aluminum relatively easily from its ors. Having said that, it's still important to recycle aluminum whenever you can, because it's still cheaper to come up with fresh aluminum by way of recycling than it is by reduction of the oars. Aluminum is everywhere. Aluminum cans for soft drinks, aluminum foils for wrapping food. Aluminum powder is used in fireworks as a propellant to actually get the firework up in the air. And like titanium, which we were talking about before, aluminum process properly is a very light but very strong metal. So that can be used along with titanium to build the holes of aircraft. I don't have any demonstrations to do for you today, but if I was going to do one, it would be this one. The thermite reaction is something we mentioned briefly in chem 101 as a way that is commonly used to well, big pieces of metal together. For example, if people are putting down a railroad tracks, what they can do is mix together some powdered aluminum and some powdered ferric oxide and set off the reaction which produces aluminum oxide and higher. But the problem is, this is a sufficiently exothermic reaction that the iron that's formed, it comes out as a puddle of liquid molten iron, which then very quickly solidifies and wills those two big pieces of metal together. Let me show you why I don't do that demonstration in class anymore. There's actually a picture of it in your textbook. It's in the margin, a page 1025. And as you can see, it produces a shower of sparks to go along with the molten iron that's being formed in the process. They used to do this in class. I decided, no, I'm tired of torching. Tabletops. I don't feel like being sued. So I don't do that when live anymore, but I'm sure you can find footage of it on the internet. Various aluminum compounds are used in many ways, aluminum oxide is found insignificant gemstones such as rubies, sapphires. There's a compound called aluminum chloral hydrate that is used as an absorber of water in anti perseverance, even in its hexahydrate. For aluminum chloride is such a good absorber of water, can it can be placed on your underarms and hopefully soak up excess moisture there. We do not recommend you use the anhydrous form of aluminum chloride to do that. Other metals in group 3a include gallium Gallium arsenide was the material that was used and some of the earliest electronic components such as transistors. And I do briefly mention thallium in my lecture notes. >> I mentioned it in the context of being used as a rat poison. >> Well, again, that's a fairly heavy metal that people don't want to have in the environment. So they found other ways to do that. That said, radioactive Valium, Valium 20 one is occasionally useful as a coronary artery imaging agent. I've had some heart operations in my time and the point is at some point they usually feed me some sample of a dye. It makes its way through my bloodstream and they can take better pictures of what's going on in the heart and the surrounding arteries. That's what I should've done. That Asian O'Brian, a picture just to convince you that I actually have a heart. But anyway, the point is this is one way that thallium compounds are used. >> Another aspect goes radioactivity in the sense of a good application for nuclear medicine. >> And we're almost finished with the metals as we move across. The periodic table. >> Group for a contains germanium, silicon, and lead. >> Excuse me, Did I say silicon? That's not silicon, that's tin. Tin occurs in nature in the form of the mineral catheter, right? Which is again an oxide of tin. Smelting using carbon as the reducing agent can get rid of the oxygen, give you ten in its metallic form. Again, these things appear in my lecture notes, but other things have taken their place. Status chloride SAN Cl2 is still occasionally uses a mile reducing agent. Status fluoride S in F2 used to be the source of fluoride ions in fluoride toothpaste, but not anymore. Now they just use sodium fluoride for that. Lead occurs in the form of a mineral called Galeano, which is basically lead sulfide. And again, the roasting and smelting process by which you first use oxygen to roast the, or get rid of the sulfur that way, and then carbon as the mild reducing agent. And the smelting process to get rid of the residual oxygen and get led by itself. You can get land from its over that way. But again, lead is another example of a heavy metal that people were trying these days to not have anything to do it for a long time. Lead was everywhere. >> Lead was in paints, lead was in additives that went into the gasoline in your car. No longer. >> Here's one that's right next to lead bismuth group 5A. And this is still commonly used, matter of fact, for those of you who were food folks, I hope you wind up in some situation where you give me cooking, good things for your customers in the restaurant or whatever, and things that don't give them upset stomachs. But if you do have a customer who occasionally gets an upset stomach, they can take Pepto Bismol. And the reason it's called Pepto Bismol is at, the active ingredient in Pepto Bismol is a compound called bismuth. Subs, politically BI C seven H five over four. And that's where the MSM in Pepto Bismol comes from. In fact, generic versions of Pepto Bismol that you can find in the pharmacy. Just say things like pink bismuth on the label. It's the bismuth that happens to have the calming effect on the stomach. And the point is that this is just a handful of some of the metals on the periodic table. We certainly don't have time to go over all of them, but we hope we've shown you enough to give you an appreciation of the rich diversity of possibilities that's out there for how we use metals and their compounds. So to wrap up for today, let me just give you an idea of where we're going from here. >> And we will turn you loops as promised earlier, our final unit of the semester will constitute a brief introduction to organic chemistry and biochemistry. >> And some of you may be going either take entire semester or a year courses in these subjects anyway. So just to see how much everybody already knows or how much people are paying attention. What is organic chemistry? And why is it going to be worth the significant part of your life to learn more about it. >> Who knows any thoughts on this? >> Why should anybody care? >> Yeah. Okay. Study of carbon, the study of living things. >> That's too good definitions of what organic chemistry is right there. Organic chemistry is largely the study of compounds that contain carbon. >> As we'll find out, carbon-based compounds make up a large number of the compounds that make up living things. >> So if you care about living things, you probably care about carbon. >> In some sense. >> There's more to organic chemistry than just carbon. Almost all organic compounds in addition to carbon, also contain hydrogen. Many of them contain oxygen and nitrogen, some of them contain halides, sulfur, phosphorus, things like that. But carbon is basically the framework, kind of like that porphyrin molecule we showed you earlier today. Single major, not organic compound that makes up most living things is water, but most of the others do have some carbon in them. So when you study organic chemistry, or studying the chemistry of the compounds that compose living things. In fact, what the word organic in this context means is that it has to do with the compounds that make up living organisms. >> For a time, people believe that there were only two kinds of substances in the universe. >> Substances that made up living things in some senses that made up everything else. And so chemistry for a while, get divided into two broad branches, organic chemistry and inorganic chemistry. Living things and not living things. Since then, we've broken it down still further because there's a bit more to it than that. And the dividing line between organic and inorganic is not as sharp as it used to be. But at any rate, we still retain the term organic to talk about compounds that make up living things. One of the other reasons that I think organic chemistry is worth studying, and of course, we will not have an opportunity to discuss every organic compound that exists in this course or the next course. But when you talk about organic chemistry, you're really talking about the chemistry of most of the compounds that exist and part of what makes carbon different from all the other elements. I said before that carbon is basically the framework for organic compounds. And the reason that's true is that carbon has an essentially limitless ability to form covalent bonds to itself. We've seen a few examples of other elements connecting up several atoms of the same element in a row, like oxygen in the form of ozone, can link three oxygen atoms to each other. Nitrogen sometimes can go as many as four. We've seen that sulfur tends to form eight Adam rings, things like that. >> That's about the best that any element other than carbon can do. >> As I've tried to indicate with this picture that I've drawn down here. >> The bottom carbon atoms can just hold hands and linked up any number of carbon atoms. >> You want. 10205000 or 1000 carbon atoms. >> No big deal. >> We've seen that before. And the kinds of compounds called polymers that we talked about. To make a polymer, you basically have to link a whole bunch of carbon atoms together. So it's this ability of carbon to form bonds to itself creates not only a whole bunch of different frameworks, but depending on what all you attached to those frameworks, an extraordinary diversity of compounds. There are over 20 million different chemical substances that have been identified, and the vast majority of them are organic compounds. So again, in Chem 100 T2 and in subsequent courses, we won't be talking about all 20 million that we hope to give you some idea of what's out there. So we will get into the discussion of organic chemistry in earnest on Wednesday. And if I'm lucky, we'll have your exams back for you at that time. >> What are they? Mm-hm. Yeah. Okay. >> We'll see. >> It would've been a good opportunity to do what you do today. Yeah. Yeah. Yeah.

chem102-010-20170501-122001.mp4

From Dana Chatellier October 11, 2018

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