About science; About the new chemistry

This is about science produced by the California Institute of Technology and originally broadcast by station K. PPC Pasadena California. The programs are made available to the station by a national educational radio. This program is about the new chemistry with host Dr. Albert Hibbs and his guest Dr. George Hammond. Here now is Dr. Hitz. A few years ago in fact enough to be in the memory of some of us at least the times were called the Age of chemistry. Of course this was preceded very soon. The age of the atom and the age of space and so on. But in spite of the fact that chemistry has lost its standing as one of the slogans of the day it seems to be charging ahead just as if that didn't matter very much. And in fact chemistry has changed considerably the subject of chemistry and the study of chemistry. And one person who's here to talk about that change is one who is participating in making a change. He's Dr. George Hammond. He holds as chair of Arthur Amos Noyes professor of chemistry at Cal Tech.

He came to calculate first in 1956 as a visitor and came back again in 58 to stay. His education was at Bates College in Maine and graduate studies at Harvard and he has recently inherited a temporary post of department chairman and I don't know whether one should congratulate you or sympathize with you George over that appointment. I think condiments would probably be more appropriate. Well tell us a little bit to set the stage of what is the historical background perhaps the recent historical background in chemistry that brings us up to the place we are now in the subject. Well I think of the last 40 years of chemistry can be described as as a golden age of structural chemistry structural. Yes. And if you consult Webster's dictionary you'll find a very good definition description of chemistry. So as a chemistry as a study of the composition and structure of matter. And a second pot study at the transformations that matter on the go was now

the first pot structure and composition is what what I like lump together a structural chemistry this is a field which is explore a model of their article that deals with talking about materials in terms of models which are well-known models of structural theory. This is under something like this then that the work on the Chemical Bond would have been developed and was developed That's right Rael a molecular structure is the heart of chemistry that's what makes That's the unique genius of chemistry which sets aside from all the sciences and chemistry we make a great deal of mileage of thinking about matter as they're all made up of molecules and then thinking about the bright detail structure of the way these molecules are organized is beautiful a repeating pattern of arrangement of atoms inside of a molecule is the real heart of chemistry. And in structural

chemistry we try to determine what's in a material and how it is internally organized on the basis of studies like this that. All of the organic chemistry and plastic development and so on was created. Well that's not quite right because the development of plastics and manufacturing chemistry depends upon really upon chemical dynamics and that is the conversion of one chemical substance into another and the exploitation of the properties that you got out of the new materials that you might want to you know something like that. The study of the structure of the DNA molecule this famous discovery of the Double Helix One fall into this general having a structural chemistry that a representative example. That's probably the up to date the ultimate accomplishment of structural chemistry is that experimental studies which lead to the theory of the structure of DNA and beautiful

elucidation. The pattern of atoms within these enormous molecules This is this is at the present time piece de resistance and now you. You say that this however is changing and something is. Replacing structural chemistry is at least more near the forefront of modern chemistry. No I think a structural chemistry is still very viable and will go on and exploring not only during the next couple of decades we're going to learn a lot more about structures of big molecules other molecules and DNA is going to be very useful. I don't want to face structural chemistry out ready to die. But I think that the big surge of accomplishment both in theory which is primarily taken from theoretical physics the application of quantum mechanics to understanding the behavior of electrons as they glue molecules together and experimental methods which have now allowed to a capability of understanding in detail a structure of these big molecules. This has been

broken through and the work will continue but it isn't going to be where I think the biggest action will occur or is actually going to occur. I think we're really right to say tremendous forging ahead in the in the area of chemical dynamics that's Websters transformation this transformation into a different structure. That's right. What what are the subjects that come under the transformation chemistry is this just how one molecule change into another fundamental uses. That's what I call chemical dynamics a systematic study of reactions and reactivity the assembling model schemes for thinking about chemical reactions which allow us to predict and control they cause of what happens chemically and what doesn't. Now the matter of people tend to think of chemical reactions as something that happened not don't happen and I think of chemists as follows tooling around in laboratories and getting

things to go on not part I classify primitive as pouring smoking liquids from one tell us another. What we really want to do is to get things to go when we want them to as fast or as slow as we want them to say that and then we have real control over our environment. And actually I think this is probably. A very important thing to remember in chemistry the way in which we can control our environment is through control of chemical dynamics. We can't do a thing about structure structure as they are in a molecule of benzene will be a molecule of benzene until it turns into a molecule of something else and we can't perturb it structure. But what we can do is to decide whether or not it's going to turn into something else by either treating it with other chemicals are by controlling conditions that preclude self-worth. This is this is why we're going to get a handle on nature through chemistry so that chemical

reactions that we're familiar with. Is it possible to learn any more about them than we already know I mean when you mix two chemicals together you get a reaction that sometimes sometimes not. And their reactions can be discovered almost without limit. There are several million known chemical compounds. And on the average every one of these has been subjected to probably 10 or a dozen reactions. And we know that limitless numbers of other reactions can be carried out. So the existence of reactions is known. So what we want to do is to. Understand these reactions in sufficient detail so that we can control and predict new ones and so that the study of chemical reactions is not a hit or miss proposition as it has sometimes been regarded even within chemistry but what are some of the examples of the ways your attacking approach dynamics how do you study. Well let me tell

you a little bit about the work that Professor Alan Cooperman is doing at Cal Tech with molecular beams molecular beam allows one to do experiments which are extremely simple conceptually gruesomely difficult to engineer but they're very easy to think about. And so they feed into the developing theory of chemical reactivity an enormously powerful information. In a molecular beam what you really do is fire one molecule at another and you have the number of molecules in the system small enough so that you can touch the molecules after they encounter each other and find out what's happened in a single collection. And this has to be contrast with the conditions under which we usually carry out chemical reactions and practical work and which typically molecules may undergo a million million collations before anything significant gets done. Now those

things which make development of theory and I mean fundamental understanding very difficult and beams experiments we're getting back to the to the grass roots of chemical change. That's one example this is done in something like a vacuum tank where you know yes in order to keep the number of molecular encounter small enough to do these Allegan experiments you really have to evacuate the system to a very very high vacuum so the number of molecules. Can being counted as as as a molecule travels from one while the other is on the average less than 1. I see. Really you do have a very good chance and in the results of getting a result of a single collision. That is one and only rarely that you have a monocle Asians and couple men's experiments are very rare indeed so rare he doesn't know when they happen. What what kind of chemicals and what kind of molecules they select for this is it a particular type that he has to select just to fit the equipment or is there a great versatility.

At the present time almost all work with molecular beams is done with a very small number of molecules primarily because there's a big problem in detecting the molecule and measuring its energy after the encounter. And most of the work has been done with the firing beams of sodium atoms and potassium atoms at very simple molecules. However the detection problem has now at least been in principle solved. And so that given enough money and enough engineering people can now begin to do experiments with large molecules at least considerably larger than what's been used before. They can choose them with a great deal of freedom and saw. Really brilliant new era experimental capability is just ahead of us. Now the modern molecular beams are apparatus which people have in mind has not yet been dealt but

we know it's there. Unfortunately the cost of a lot of money. Well Ken is it possible with the expense of a particular choice of atoms and molecules that go home and starting out with now that he can with theory I guess a proper way to ask the question is is the theory developed well enough so that he can extrapolate from these rather simple results to what would happen in a more complex case or does each particular reaction have to be studied by itself in order to understand it at the present time. Theory of scattering. That's that's the general theory of what happens a molecular collision is really in its infancy and it isn't. Yeah viable for extrapolation. But what's going right now is that the fundamentals of the theory are being built up with these very simple model experiments and of course you're going to get a particular line of research.

And of course it's a very great hole. Extrapolate of theri will will be developed as a field comes along. That's everyone's ambition. As you close to getting as his money and his equipment by the way was it fair to ask that it's perfectly fair to ask and he's not close and I think that this is a place where chemistry will probably have to adopt some of the style of modern physics experiments are going to be complex enough so that what will have to be done is that area facilities will be established in which. A particular kind of experiment is done at a very advanced level and visitors come from other universities and national laboratories and so on from this molecular beam equipment that is approaching the size of a physical accelerator physics accelerator. I would say it's approaching the size of a midget accelerator. I weigh the costs and the magnitude of the operation don't compare with allied to accelerators. But the cost us afresh to make the problem at least to the

experimental chemist the same sort of say yes to war really worked very hard to organize enough funds to do a single very important explore our own principles even this could be done after all of physics has established a method and it seems to work very well so one would guess this could work. So I guess it would work of course a certain amount of resistance of the resistance from funding agencies in fact of course right at the present time as a resistance of all agencies which is processed on them from outside to not find anything new. Right. And there was also a certain amount of resistance from chemists chemists as a group tended to be rather highly conservative and to have developed a preference for small experiments. Chemist sometimes say that they're doing small science like this concept has a certain amount of the levity to it but it obviously can do some of the jobs that we now see before us to be done you know in principle capable.

And ambition to do things as is outstripping I capability to stick with a pure small science objective. Your own work I believe is involved in chemistry and radiation chemistry primarily what what are these fields what is for all that radiation is out for the chemistry as chemical change caused by absorption of light and by this we almost always mean visible light or light in the near ultraviolet part of the spectrum. High energy radiation chemistry is a chemical change caused by radiation having much higher. A lot of energy per quantum. By this we mean radiation with gamma rays x rays fast slow electrons that is based upon a different strain it too is just primarily what part of the spectrum you're talking about them. Yes and this difference in the part of the spectrum is not a trivial thing. It means that the fundamental acts in the high energy radiation chemistry are

just vastly more complex than those and photochemistry. What are some of the typical lines of work that are going on in photochemistry. Well at the present time one of the things that we're doing is focusing attention on the chemical properties of excited molecules to produce an excited molecule by absorbing light and you get a very large amount of X attention an idea that's a real jolt. And because the energy comes in in a large quantum. Molecule has a great deal of difficulty in finding a way of shutting it. You know it's it's not a simple thing because it either has to spit it back out again by letting light and this is luminescence R. It has to break up this quantum into smaller bets so it can be shut off in the forms of all energy of motion and vibrational energy and so forth.

And fluorescence I guess if it just gives out to other quanta are smaller. That's right. Fluorescents as one kind of luminescence. And that would come under photochemistry than this. Yes this is I thought a chemistry that didn't happen. See the energy stays in there and turns the molecule under something else because I know that assassination that's part of chemistry. What about the what about the change that happens and you know photographic motion when the light hits it is that the photochemistry. Yes it certainly yes. How does that work because it's not known yet what the process a great deal is known about it. What happens is that a silver chloride a silver bromide molecule is decomposed on a solid grain of the cell of our Hale I'd producing cells are out arms and chlorine atoms chlorine atoms disappear they are consumed chemically in the rest of the system and then the development process simply takes advantage of the sensitize ation of the grain

by this first few whacks of photo d composition. That's actually photography has two stages as a first stage of which is for the chemistry in which a grain is prepared to do something and then the developing as a pure non-thought a chemical act that takes advantage of that and that amp amplifies the effect. I see I'm sure you realize that another important part of chemical reaction that everyone is familiar with is photosynthesis then process going on in green plants. Which is without which none of us would be here. I try John which of the lifecycle on this planet depends totally. Have you been looking at that particular one by the way we have not been looking at photosynthesis hollow Wells Robinson and Cal Tech has been doing some work with photosynthesis we've been looking at smaller molecules than chlorophyll chlorophyll penguin and green pigment and plants as a fairly complex system. And we're conservative we've stuck

by lives to small molecules with the hope that we'll learn more. That's maybe a mistake. And our attention has been on one of the properties of an excited molecule. What allows it to undergo a chemical change as opposed to re emitting light has fluorescent cell phosphorescence or in breaking the energy up into small bits and just shocking it off into the solution. That's that's of course the most terrible thing that can happen to an excited molecule like back out. All you've done is used a lamp to warm up the solution alone. That and that's that's a terrible waste of. Light energy. Oh and this is this work that you've done is also included. However the high energy radiation chemistry and connection between the two. Other than the fact that they're both light. Oh yes there's a connection because the reason that we're not high energy radiation field is that we're using the results of our thought of chemical studies to try and unravel the more complex processes that go on in high energy

radiation chemistry and using them in a theoretical sense you mean just now an experimental set up. We take a system which we pretend we know all about photographically. Now this may be wrong but it's a good thing to Burketown and I would put it into a solution and write it with gamma rays and we see what happens to it chemically and some of the chemical advance will turn out to be the same as for a chemical advance some of them different even though the radio Gamma Gamma radiation is much higher. That's right and why is that. Well this is because well let me tell you what happens when a gamma particles through a solution. OK first of all I have great penetrating power which means that they go through matter usually without interacting with it once in a while. Strong interaction will occur and when it does the molecule that interacts with it becomes very excited in fact it blows up spits out an electron. Now these electrons which I spat out in that process are themselves fairly high energy particles and they

start shooting off at quite a great rate but they slow down fairly rapidly in the process of slowing down they transfer energy to molecules in the medium and get them excited. And some of these secondary excitations will correspond to the same excitations that are observed in our absorption of light. Some don't. We know that a good deal about the various kinds of excitation that can come out of an experiment like this. But we don't know how much of each kind of excitation process goes on. And so what we do is to use our photo chemical monitors stick them in and diagnose this part of the chemistry as occurring from the same excited state you get when light is absorbed and the rights come from something else. And this goes back. I presume you can trace this back and what happened from the original game interaction. What kind of breakup occurred was this when you get back to that.

That's almost all of one kind. This is nearly all injection of high energy electric and that's so that's pretty much I think pretty well. That's pretty much the same whether or not the exciting thing is a gamma ray or an alpha particle or a beta product. And you think you understand some of the secondary processes that go on so what you're trying to track down is what the other processes. And while we're finding out how much of it on the net at the end of factors like photochemistry how much yet. And then we go in with other probs and try to take apart the rest of it and get that. Divided in a pot so much coming from raw actions of I and some of it coming from reactions of free radicals and software I will really have a whole battery of two tools on molecules that we think we understand we shot these things and we pull out a piece of a piece of chemistry and we say aha that says that we had so much of this kind of excitation process

and I was sort of fun in this line of research is it possible to get a better understanding of what happens in a biological medium when high energy radiation hits it why what is the process of radiation damage to a living creature. Oh a good deal of work is being done on that fact. Radiation damage and photo chemical damage of nucleic acids has been a very hot field in the past five years and a great deal is known. For example we know exactly how ultraviolet light destroys denatures nucleic acids. You know this in great detail and we suspect that the excitation process that goes on with gamma radiation is somewhat similar to a low gamma radiation again as it is more complex. If you shine a light on a piece of biological material containing DNA you can under proper circumstances know what most of the light has gotten into

the DNA. The gamma particles. Are not selected that will excite everything. DNA all the biological materials water or gamma particles rays the double with water break it up into electrons and hydrogen atoms hydroxyl radicals and these things turn around again attack biological materials including attacking DNA. Oh it's not just secondary particles that come off and it's actually some of the chemical products that are released that also attack the DNA. That's right these are these are secondary excited species are responsible for probably most of the damage which goes on and. Radiation with biological materials. Is it possible that any of the tools which you were using simply to understand the process better will themselves have application to control radiation affects our limit radiation effects.

Well that's a knotty question because I can answer it with great decision with respect to certain kinds of materials. Non-living material you can probably devise excellent methods of protection against both light and high energy radiation simply by impregnating it by when the Tarryall is which will pick up the energy and degrade it to thermal energy with high efficiency without undergoing chemical change. And these materials will be particularly susceptible to picking up the energies. Oh yes we have that all under control at least in principle. However there's a real problem when you come to living systems. And this arises from two sources. First of all living systems are fussy and we have to worry about toxicity. You can't kill the animal or protecting it from radiation does very little good. And the second is that mobility in a biological system is very great the body fluids are forever moving around they'll pick up things move them off and

dump them in straight corners well they do no good and don't protect the material has to be at the site where the energy would be absorbed so that it can take care of it and degrade it. Most are any indication of substances of that type which saw all these multiple needs of a living system protection will be found. It's only a gas and the present time I would guess that they probably will be found but they'll have to be used with great care because they're going to have to be substances very closely related to the biological materials themselves in order for them to get to their assigned place and stay there. They've almost they've got to half an hour into the biological system. And things that do that are unfortunately frequently turn out to be highly toxic because they fake out the living system in other ways too and sometimes tend to kill it. Is there any connection between the work that Cooperman is finding which is molecular

beams and the kinds of reaction he's looking at and the kinds of reactions that you're looking at with the photochemistry and radiation chemistry. A very great deal of relationship. First of all we tie them together by therapy we talk and get along very well. Second way when I'm talking about proper behavior I'm an excited molecule I'm talking about a very energy rich molecule. And among other things I'm talking about how it does or it doesn't transfer this energy to some other part of the system. This is very light. The elementary energy transfer processes that that woman studies in this molecular collations and molecular study of chemical dynamics and this group is related even though it may look different on the outside. George thank you very much for joining us tonight and telling us about the new directions that you're following in chemistry and chemical dynamics. This was about science with host Dr. Albert Hibbs and his guest Dr.

George Hammond join us again for our next program went to more prominent scientists will discuss a subject of general interest about science is produced by the California Institute of Technology and is originally broadcast by station KPCC in Pasadena California. The programs are made available to this station by the national educational radio network.