Fluorination and Atomic Energy
By E.T. McBee
Early in 1942 Purdue chemists were called in as consultants on that most awesome of the war’s scientific ventures, the development of atomic energy for military purposes. In June of the same year, the Department, because of its background of experience in fluorine chemistry, was asked to accept, through the Purdue Research Foundation, a small contract to investigate the preparation of the bis(trifluoromethyl) benzenes, of which there are three isomers, and two of the three isomeric tris(trifluoromethyl) benzenes. These materials were to be used as intermediates in the preparation of the corresponding fluorocarbons—i.e., compounds containing only carbon and fluorine. Before the contract was four months old, the budget was increased and the scope of the research expanded to include an investigation of methods for the preparation of fluorocarbons.
These materials were not only new materials but also they were products essential for the operation of on of the huge plants at Oak Ridge, Tennessee, in which the isotope U-235 was separated from isotope U-238.
The preparation of perflueroheptane [sic], one of the desired fluorocarbons, by reacting heptane with elemental fluorine was investigated at Columbia University. Since fluorine reacts with most organic materials with explosive violence, even at low temperatures, another procedure was desired for use in large scale production. Purdue chemists, along with others, found that certain metal fluorides, prepared by the use of fluorine give a smooth reaction with heptane and with other hydrocarbons. As a result of this reaction fluorocarbons were obtained. A process utilizing this reaction was adopted for the commercial production of perfluoroheptane.
At the beginning of the investigation, fluorine was being made in small amounts at an estimated cost of about $75 per pound. Because of the difficulty in its preparation and because of its highly corrosive nature, there was considerable doubt that it could be produced in the quantity necessary for the production of the desired materials. Therefore it seemed desirable to find a methods for the preparation of fluorocarbons using as little fluorine as possible. Purdue chemists proposed using hydrogen fluoride available in quantity at 15 cents per pound. Several possibilities were investigated; a process was developed for the preparation of bis(trifluoromethyl) benzene which was carried out in approximately a two and one-half million dollar plant at Niagara Falls. This compound was then converted to the fluorocarbon dimethylcyclohexane in approximately a forty million dollar plant in New Jersey.
Later, Purdue chemists developed an alternate and a standby process which produces both perfluoroheptane and an alternate for perfluorodimethylcyclohexane. In this process, which was operated in pilot plants, a relatively small amount of fluorinating agent which required fluorine for its preparation was needed. Details about it and about many variations in procedures would be more appropriate in a paper for chemists than for presentation here.
It might be said, by way of interpolation, that organic fluorine-containing compounds offer tremendous scientific and industrial possibilities. Fluorocarbons, for example, are the most stable known organic compounds. They fail to react with most substances and they are non-inflammable. The prediction may be made that many fluorine-containing medicinals will appear in the future, for at Purdue a fluorine-containing compound has already been developed which possesses properties approaching those of an ideal anesthetic. There are many more fluorine-containing compounds theoretically possible than all the compounds known today. Since there are more than 300,000 known compounds, it is readily seen that research workers in fluorination are not likely to run out of problems.
When the Purdue chemists were about to finish their work on the preparation of fluorocarbons, they were asked to help with the chemical problems associated with another of the processes for the separation of the isotope U-235 and U-238. Security regulations, at the time of this writing, do not permit a discussion of the work done in connection with the process. However it may be said that in general the investigations were conserned (sic) with the recovery of uranium.
The Purdue chemists did about an equal amount of research on both problems. In all, counting graduates, service staff, and members of the permanent staff, more than 100 persons were employed on the project, with a budget of more than $700,000.
Transcribed from United States Atomic Energy Commission – Oak Ridge, Tennessee - Original Document
Date of Declassification: 10/29/46