At the root of all science, including organic chemistry, is people’s unquenchable curiosity about the world and themselves. Everywhere are objects, living organisms, and events that people have had questions about. Scientists investigated these questions and discovered other questions. They investigated these new questions and found still more questions. Research, they learned, not only answers questions but uncovers new ones. Although scientists have learned many answers, they also have found that the answers to some questions must wait for the development of better investigative methods and tools. The job of scientists is to find answers to the multitude of questions about the world and to develop better methods and tools to answer the more and more sophisticated questions that they come up with along the way.
Because much of the world is based on the chemistry of carbon, organic chemists have provided many answers to the questions about the world. Many creative and curious people have been attracted to organic chemistry. The following stories illustrate the hard work and ingenuity of two such chemists.
In 1874, Othmer Zeidler reported the synthesis of DDT in his
Because much of the world is based on the chemistry of carbon, organic chemists have provided many answers to the questions about the world. Many creative and curious people have been attracted to organic chemistry. The following stories illustrate the hard work and ingenuity of two such chemists.
In 1874, Othmer Zeidler reported the synthesis of DDT in his
doctoral dissertation. Some years later, Paul Hermann Müller discovered the insecticidal properties of DDT and in 1948 received the Nobel Prize in Medicine and Physiology for his discovery. Today DDT has a bad reputation because of its persistence in the environment. Its intended use was to kill disease-bearing insects, but it also caused harm to a number of birds and animals. DDT is no longer used in most areas of the world, but in the 1940s it was a “magic bullet” that killed many disease-bearing insects and saved many hundreds of thousands of lives. During World War II, the military used DDT, but it was not available for civilian use until Frank Mayo happened to read about it.
Frank Mayo is an example of an ambitious person who, with determination and hard work, coupled with a sound chemical foundation, made an impact on society (See Friedman, J. Chem. Educ., 1992, 69, 362). Mayo attended Georgia Tech leaving just one semester from completing the three year degree in chemistry. He turned down a job offer for eighteen dollars per week because he thought he could earn more working on his father's farm.
A few years later he began manufacturing and marketing chlorine based bleaching compounds. In 1944, while looking for other products to manufacture, Mayo happened on an article in the Atlanta Constitution describing DDT and its uses. He became interested. DDT was available only to the military; but even there, it was available only in limited quantities. The article stated that the synthesis for DDT was classified. However, it did give one important clue—a brief mention of the original synthesis by Zeidler in Germany. That was just enough information for a determined chemist!
Mayo knew that usually graduate students published their doctoral dissertations four to six months after graduation. He also knew that Othmer Zeidler received his degree in May or June of 1874, so Mayo expected to find the published report in the renowned journal Berichte der Deutschen Chemischen Gesellschaft (Reports of the German Chemical Society) by October, 1874.
Mayo went to the Georgia Tech library but found they did not begin subscribing to Berichte until 1910. Nearby Emory University began in 1915. He next decided to try the University of Georgia library 75 miles away in Athens. Since his daughter Bebe was a student there, he phoned her and asked her to check the library for him.
She found that indeed the University of Georgia had the 1874 issues of Berichte, but they were in boxes stored in the attic of the library. Only after many delays and much persuasion did Bebe gain permission to look through the issues Berichte in the attic. The librarians were notably reluctant to get them out of storage for a freshman who was studying neither German nor Chemistry. Bebe examined the title pages of the 1874 volume of Berichte beginning with October. “Believe it or not,” says Mayo, “There it was, in the October issue.” Word for word in the unfamiliar German, Bebe copied the paper by hand, then she called her father.
Mayo rushed to Athens, only to arrive after visiting hours in the dormitory. They wouldn't even let a father see his daughter after visiting hours! He drove around the dormitory, parked under his daughter's window and honked the horn. Bebe placed the transcript in an envelope and threw it out the window. Carefully shielding the paper from the falling rain, he read Bebe's copy in the headlight of the car then immediately drove back to Atlanta. He had the synthesis of DDT!
The synthesis required three ingredients: chlorobenzene, sulfuric acid, and chloral. He already had the chlorobenzene and sulfuric acid, but he had no chloral. Ignoring the fact that it was midnight, he drove to the neighborhood druggist and asked for a pound of chloral. The sleepy druggist grumpily informed him that he needed a prescription, and that no physician was likely to give him a prescription for a pound of the stuff. The typical prescription for chloral was measured in minims (about 16 minims per milliliter).
Mayo explained the reason for wanting the chloral, and the druggist finally agreed to sell him a pound.
With the precious chloral in hand, Mayo went home to try to make DDT. He measured the chemicals into a fruit jar packed in ice, using a wooden kitchen spoon to stir the mixture. Twenty minutes later, floating white lumps covered the top of the liquid. He separated the solid from the mixture with a buttermilk strainer and dried the powder. Then he slept.
The next morning, he made up a 5% solution in mineral spirits and sprayed the laundry area of his basement. Fleas from his dogs infested the area. An hour later, he and his wife returned to the basement. “Not a flea jumped to my wife's ankles,” he said. “Nothing happened—no fleas! The fleas, formerly plentiful, were dead. Cockroaches were lying with their feet in the air as if waving good bye to me. I was a happy man.”
Mayo then built a plant to manufacture DDT. Because of the war, he could not buy the equipment he needed. However, being resourceful, he built his plant with scraps and old metal drums that most people would consider junk. Mayo made hundreds of thousands of pounds of DDT powder and DDT solutions in deodorized kerosene and shipped it all over the world. Because of the benefit DDT gave to people, Mayo received much praise. Later, problems showed up that scientists traced to DDT so he stopped making and selling it. Since the banning of DDT, insect born diseases are again on the rise, but because DDT causes damage to helpful animals, it is not an acceptable insecticide. So far no one has discovered a good substitute.
Are you ever heading in one direction with a particular project only to find it turning out differently than you had expected? Do you just junk the project, or do you find yourself trying to figure out what went wrong or how you can use the project some other way? Many of the great discoveries of chemistry were made because the chemist investigated the reasons for an unexpected result. That was the case for Roy J. Plunkett, a young Ph.D. chemist who graduated from Ohio State University in 1936.
Plunkett was working for DuPont attempting to find a non-toxic refrigerant. On April 6, 1938, he and his assistant, Jack Rebok, opened the valve on a cylinder of tetrafluoroethylene to begin an experiment. No tetrafluoroethylene came out. In fact, nothing came out, although the weight of the tank indicated it should be full. He pushed a wire into the valve to determine if it was blocked. The wire went in freely. Plunkett had no understanding of what was wrong, but instead of discarding the “empty” tank and getting another to continue his research, he decided to investigate. Sawing the tank open, he found it filled with a waxy white powder. The molecules of tetrafluoroethylene had reacted together to form a polymer, or plastic, that they called polytetrafluoroethylene.
No one had ever observed the polymerization of tetrafluoroethylene before, but somehow it had occurred inside an otherwise “empty” tank. What caused it? On further investigation, Plunkett found some iron oxide inside the tank and discovered that it had catalyzed the polymerization reaction. Plunkett and other DuPont investigators soon developed ways to make polytetrafluoroethylene.
This new polymer had some remarkable properties. It was inert—it would not react with either strong acids or strong bases. It was heat stable, and no solvent could dissolve it. It was also extremely slippery. In spite of these interesting properties, if it had not been for World War II, probably no one would have done anything with it. Tetrafluoroethylene was too expensive.
General Leslie R. Groves happened to hear about the new material and asked to test it. General Groves was in charge of the Manhattan Project, the group working to develop the atomic bomb. In their research, they used enriched uranium. To make the enriched uranium, they converted uranium to uranium hexafluoride, an extremely corrosive gas. The project needed a gasket material that was resistant to uranium hexafluoride, so DuPont made some gaskets and valves for Groves. The scientists at the Manhattan Project tested them and found them very resistant to uranium hexafluoride. DuPont manufactured Plunkett's polymer for the Manhattan Project under the name TeflonTM.
Unlike DDT, Teflon's usefulness has stretched well beyond its wartime beginnings. Who hasn't used Teflon coated cookware? Of greater significance than the cookware is the fact that Teflon is a substance that the body does not reject. Thus, millions of people have benefited by receiving such things as artificial hips and knee joints or aortas and pacemakers made of Teflon. Another use of Teflon is in the space program. Space suits, wire and cable insulation, spaceship nose cones, and fuel tanks all use Teflon.
Frank Mayo is an example of an ambitious person who, with determination and hard work, coupled with a sound chemical foundation, made an impact on society (See Friedman, J. Chem. Educ., 1992, 69, 362). Mayo attended Georgia Tech leaving just one semester from completing the three year degree in chemistry. He turned down a job offer for eighteen dollars per week because he thought he could earn more working on his father's farm.
A few years later he began manufacturing and marketing chlorine based bleaching compounds. In 1944, while looking for other products to manufacture, Mayo happened on an article in the Atlanta Constitution describing DDT and its uses. He became interested. DDT was available only to the military; but even there, it was available only in limited quantities. The article stated that the synthesis for DDT was classified. However, it did give one important clue—a brief mention of the original synthesis by Zeidler in Germany. That was just enough information for a determined chemist!
Mayo knew that usually graduate students published their doctoral dissertations four to six months after graduation. He also knew that Othmer Zeidler received his degree in May or June of 1874, so Mayo expected to find the published report in the renowned journal Berichte der Deutschen Chemischen Gesellschaft (Reports of the German Chemical Society) by October, 1874.
Mayo went to the Georgia Tech library but found they did not begin subscribing to Berichte until 1910. Nearby Emory University began in 1915. He next decided to try the University of Georgia library 75 miles away in Athens. Since his daughter Bebe was a student there, he phoned her and asked her to check the library for him.
She found that indeed the University of Georgia had the 1874 issues of Berichte, but they were in boxes stored in the attic of the library. Only after many delays and much persuasion did Bebe gain permission to look through the issues Berichte in the attic. The librarians were notably reluctant to get them out of storage for a freshman who was studying neither German nor Chemistry. Bebe examined the title pages of the 1874 volume of Berichte beginning with October. “Believe it or not,” says Mayo, “There it was, in the October issue.” Word for word in the unfamiliar German, Bebe copied the paper by hand, then she called her father.
Mayo rushed to Athens, only to arrive after visiting hours in the dormitory. They wouldn't even let a father see his daughter after visiting hours! He drove around the dormitory, parked under his daughter's window and honked the horn. Bebe placed the transcript in an envelope and threw it out the window. Carefully shielding the paper from the falling rain, he read Bebe's copy in the headlight of the car then immediately drove back to Atlanta. He had the synthesis of DDT!
The synthesis required three ingredients: chlorobenzene, sulfuric acid, and chloral. He already had the chlorobenzene and sulfuric acid, but he had no chloral. Ignoring the fact that it was midnight, he drove to the neighborhood druggist and asked for a pound of chloral. The sleepy druggist grumpily informed him that he needed a prescription, and that no physician was likely to give him a prescription for a pound of the stuff. The typical prescription for chloral was measured in minims (about 16 minims per milliliter).
Mayo explained the reason for wanting the chloral, and the druggist finally agreed to sell him a pound.
With the precious chloral in hand, Mayo went home to try to make DDT. He measured the chemicals into a fruit jar packed in ice, using a wooden kitchen spoon to stir the mixture. Twenty minutes later, floating white lumps covered the top of the liquid. He separated the solid from the mixture with a buttermilk strainer and dried the powder. Then he slept.
The next morning, he made up a 5% solution in mineral spirits and sprayed the laundry area of his basement. Fleas from his dogs infested the area. An hour later, he and his wife returned to the basement. “Not a flea jumped to my wife's ankles,” he said. “Nothing happened—no fleas! The fleas, formerly plentiful, were dead. Cockroaches were lying with their feet in the air as if waving good bye to me. I was a happy man.”
Mayo then built a plant to manufacture DDT. Because of the war, he could not buy the equipment he needed. However, being resourceful, he built his plant with scraps and old metal drums that most people would consider junk. Mayo made hundreds of thousands of pounds of DDT powder and DDT solutions in deodorized kerosene and shipped it all over the world. Because of the benefit DDT gave to people, Mayo received much praise. Later, problems showed up that scientists traced to DDT so he stopped making and selling it. Since the banning of DDT, insect born diseases are again on the rise, but because DDT causes damage to helpful animals, it is not an acceptable insecticide. So far no one has discovered a good substitute.
Are you ever heading in one direction with a particular project only to find it turning out differently than you had expected? Do you just junk the project, or do you find yourself trying to figure out what went wrong or how you can use the project some other way? Many of the great discoveries of chemistry were made because the chemist investigated the reasons for an unexpected result. That was the case for Roy J. Plunkett, a young Ph.D. chemist who graduated from Ohio State University in 1936.
Plunkett was working for DuPont attempting to find a non-toxic refrigerant. On April 6, 1938, he and his assistant, Jack Rebok, opened the valve on a cylinder of tetrafluoroethylene to begin an experiment. No tetrafluoroethylene came out. In fact, nothing came out, although the weight of the tank indicated it should be full. He pushed a wire into the valve to determine if it was blocked. The wire went in freely. Plunkett had no understanding of what was wrong, but instead of discarding the “empty” tank and getting another to continue his research, he decided to investigate. Sawing the tank open, he found it filled with a waxy white powder. The molecules of tetrafluoroethylene had reacted together to form a polymer, or plastic, that they called polytetrafluoroethylene.
No one had ever observed the polymerization of tetrafluoroethylene before, but somehow it had occurred inside an otherwise “empty” tank. What caused it? On further investigation, Plunkett found some iron oxide inside the tank and discovered that it had catalyzed the polymerization reaction. Plunkett and other DuPont investigators soon developed ways to make polytetrafluoroethylene.
This new polymer had some remarkable properties. It was inert—it would not react with either strong acids or strong bases. It was heat stable, and no solvent could dissolve it. It was also extremely slippery. In spite of these interesting properties, if it had not been for World War II, probably no one would have done anything with it. Tetrafluoroethylene was too expensive.
General Leslie R. Groves happened to hear about the new material and asked to test it. General Groves was in charge of the Manhattan Project, the group working to develop the atomic bomb. In their research, they used enriched uranium. To make the enriched uranium, they converted uranium to uranium hexafluoride, an extremely corrosive gas. The project needed a gasket material that was resistant to uranium hexafluoride, so DuPont made some gaskets and valves for Groves. The scientists at the Manhattan Project tested them and found them very resistant to uranium hexafluoride. DuPont manufactured Plunkett's polymer for the Manhattan Project under the name TeflonTM.
Unlike DDT, Teflon's usefulness has stretched well beyond its wartime beginnings. Who hasn't used Teflon coated cookware? Of greater significance than the cookware is the fact that Teflon is a substance that the body does not reject. Thus, millions of people have benefited by receiving such things as artificial hips and knee joints or aortas and pacemakers made of Teflon. Another use of Teflon is in the space program. Space suits, wire and cable insulation, spaceship nose cones, and fuel tanks all use Teflon.
No comments:
Post a Comment