19th century French physicist Henri Poincaré said: "The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing, and if nature were not worth knowing, life would not be worth living." This idea applies perfectly to one scientist here at Wesleyan, Professor Wallace Pringle: an expert in the field of Physical Chemistry, an environmental activist, and perhaps most importantly, a lover of teaching, in which he shares his passion with others. Speaking about his love for chemistry in the way it constantly surprises him, Pringle says: "You think you know what you're going to see, and you see something else, and that is what's most interesting. Because if you could predict what you're going to see, it's not very interesting, or all you're doing is confirming a theory that already exists. So the most fun is when you see something unusual." I had the opportunity to speak with Professor Pringle recently. In the process, I was able to figure out just what a spectrometer, the device used by Pringle in his spectroscopy experiments, is.
Spectroscopy concentrates on the interaction of light and matter, and is the primary area of focus for Professor Pringle's studies in physical chemistry. Other areas of great interest to Pringle are: the structure of small-ring molecules, which despite their minute size are quite complicated in nature; the nature of van der Waals bonds, specifically their structure, and the effects of altering these bonds; and water chemistry, which corresponds to many of Pringle's environmental interests. By focusing on microscopic molecules, physical chemistry aims at understanding the larger systems which we encounter in everyday life.
In studying spectroscopy, Pringle is actually aiming at studying series of spectra: a continuum of color formed when a beam of white light is dispersed such that its component wavelengths are arranged in order. An example of this is when light passes through a prism. The result of such a dispersion is something akin to a rainbow.
Of course, spectroscopy extends far beyond the examination of a mere prism. National organizations such as the U.S. Geological Survey use spectroscopy to map the vegetation of national parks, to search for abandoned land mines, and even to study soil. Knowledge about the spectra of the planets and satellites has been gained through investigation using spectroscopy. Recent research in the area of spectroscopy has focused largely on the use of lasers and microwave technology.
Pringle's most current research in spectroscopy is based around the perturbing of small ring molecules (in other words, destabilizing otherwise balanced forces), and then trying to measure the effect on the van der Waals bond which results from this altered balance of forces. In order to do this, an argon atom is placed on the small molecule at an extremely low temperature, which actually acts to produce a van der Waals bond (says Pringle of the van der Waals bonds in this experiment: "We have to measure them in a high vacuum spectrometer that has a temperature around zero Kelvin, and that's how they stay cold enough to even stick together"). The van der Waals bond may then be measured by using spectroscopic equipment. Pringle explains this experiment by stating: "we're using another molecule to be a probe of van der Waals forces."
Van der Waals bonds are forces responsible for holding gas molecules in order. They are also the forces responsible for causing gases to condense into liquids. While van der Waals bonds have a tremendous effect in the natural world, these chemical forces are rather weak. Professor Pringle says of van der Waals forces: "They're thousands of times weaker than normal chemical forces, and they are not well understood, because they're very difficult to calculate and they're very difficult to measure." Were van der Waals bonds not present, substances such as gasoline could not even exist (for gasoline's structure is composed of van der Waals bonds).
Within gas molecules, much is measured in the study of spectroscopy. The interactions of gas molecules with one another (when the molecules come into collisions) result in induced dipole moments. A dipole moment is the product of the distance between the two poles of a dipole, and the magnitude of either pole. These induced (induced meaning that their interactions are planned out in the laboratory) dipole moments can be observed with high vacuum spectrometers, in a carefully designed environment of high pressure.
Professor Pringle is not merely studying gases, but is also currently focusing on the chemical properties of water. He is interested in the chemical reactions associated with ozonolysis in water. Ozonolysis results from the sun's ultraviolet rays hitting a body of water. These rays actually irradiate the water (irradiation is an altering of the van der Waals bonds that hold the water itself together), as can be detected by using advanced spectroscopy equipment.
Professor Pringle is also quite active outside of the classroom and the laboratory. He has been on an advisory committee to the lung association committee, and was Chairman of the Planning and Zoning Commission in Connecticut. His understanding of physical chemistry has proven quite valuable in application to the real world, when it comes to Environmental Chemistry. Pringle says of the need for studying Physical Chemistry when engaging in Environmental Chemistry: "let's say if you wanted to understand something like the stratospheric ozone depletion problem, almost all the science associated with that is physical chemistry science. You'd have to be able to measure molecules in the atmosphere, you have to be able to understand how they're going to react, you have to be able to do the reactions in the laboratory in the gas phase, and that's all physical chemistry."
There are many ways in which the study of physical chemistry can help save the environment. For example, knowing some common chemicals hazardous to the environment, and knowing how to prevent the two from coming in contact could help save thousands of gallons of water, or even prevent an oil spill. The study of physical chemistry can thus not only help the environment by keeping it contaminant-free, but possibly even save lives.
Finally, Professor Pringle speaks of his passion
for teaching and studying Physical Chemistry, such that he feels he never
stops learning simply from the process of teaching. Professor Pringle says:
"how you get to be an expert is you can teach your way into being an expert,
or learn your way. So the good thing about teaching is you're always learning
something, there isn't a day that goes by that you don't learn something
important, and if it does, you should stop. A day goes by without learning
anything important, you really ought to stop. And I haven't stopped yet."
Some of Professor Pringle's works include:
1. "Determination of the Structure of the Argon Cyclobutanone van der Waals Complex by M.R. Munrow, W.C.Pringle and S.E.Novick J. Phys. Chem. 103, 2256(1999)
2. "Collisionally-Induced Rotational Spectrum of Allene" W. C. Pringle, S. M. Jacobs, D. Rosenblatt, Mol. Phys. 50, 205 (1983).
3. "Analysis of the Collision Induced Far-Infrared Spectrum of Ethane" R. Cohen, W. C. Pringle, Spectrochimica Acta 42A, 291 (1986).
4. "Analysis of Collision Induced Far Infrared Spectrum of Ethylene" W. C. Pringle, R. Cohen , S. M. Jacobs, Mol. Phys. 62, 661 (1987).
5. "Collision Induced Far Infrared Spectrum of
Cyclopropane" W. C. Pringle, W. R. Gronlund, R. C. Cohen, Mol. Phys. 62,
669 (1987).
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LINK TO WRITING ABOUT SCIENCE (CHEM 180) HOME PAGE: http://www.wesleyan.edu/~tklassen/chem180
LINK TO PROFESSOR PRINGLE'S HOME PAGE: http://www.wesleyan.edu/chem/faculty/pringle/
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