Synthesis of 1-(2-thienyl) thialkane and attempted synthesis of alkyl substituted thiacyclohexanes
Wang, Jean Yii-Chan
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It has been known for some time that the sulfur compounds in petroleum products were both obnoxious and detrimental. Therefore, it was essential that they be removed from the crude petroleum during the refining processes. Unfortunately the removal of the sulfur impurities was not readily accomplished and also was rather costly. Consequently many oil fields containing crudes rich in sulfur have been bypassed. Such extravagances of course could not be continued and petroleum chemists have for many years been in search of better and more economical methods of removing the sulfur impurities. The thought occurred, to those working in this fields that if the chemical structures of the sulfur compounds could be determined, a better method for their removal might be forthcoming. In 1948, the American Petroleum Institute initiated a research project designated as A.P.I. R.P. 40, the purpose of which was to coordinate the work groups and to actually speed up the efforts of the workers involved. The Chemistry staff at the Texas Woman's University became associated with the American Petroleum Institute at the Bureau of Mines in Bartlesville, Oklahoma in 1955, and has been making worthwhile contributions since that time. As reported by previous workers in this laboratory, the method of identification of the sulfur compounds was an indirect one in that the structure was based on a comparison of the chemical and physical properties of the isolated sulfur compounds with the synthetic compounds. If the properties were identical in all cases, it could be assumed that the structures were identical. The primary objective of this research was the preparation of a series of 1-(2-thienyl) thialkanes to serve as reference standards in the search for similar structures in petroleum. The compounds of this type prepared during the course of the investigation were members of two isomeric groups. Namely, 1-(2-thienyl)-3-thialkanes and 1-(2-thienyl)-4thialkanes. The compounds synthesized and sent to the Bureau of Mines at Bartlesville for further study were: 1-(2-thienyl)-3-thia-4-methyl pentane; 1-(2-thienyl)-3-thiahexane; 1-(2-thienyl-3-thia-4-methylhexane; 1-(2-thienyl)-3 thiaheptane; 1-(2-thienyl)-3 thianonane; 1-(2-thienyl)-3-thiadecane; 1-(2-thienyl)-3-thiaundecane; 1-(2-thianyl)-4-thia-5-methylhexane; 1-(2-thienyl)-4 thiaheptane; 1-(2-thienyl)-4-thia-5-methylhexane; 1-(2-thienyl)-4-thiaoctane; 1-(2-thienyl)-4-thiadecane; 1-(2-thienyl)-4-thiaundecane; and 1-(2-thienyl)-4-thiadodecane. A secondary objective of this research was to explore a new synthetic approach to alkylthiacyclohexane derivatives. Previous workers in this laboratory investigated several methods of approach to synthesis of this type but without any appreciable success. The new synthesis involved a Dieckmann condensation of substituted beta thio diesters. Preliminary work has indicated that this approach should be a successful one. It is hoped that investigation will be continued on this synthetic method but unfortunately time did not permit seeing it through to the point of fruition at this time. In view of the fact that the 2-alkylthiophenes seemed to break down in the definite patterns on mass spectral analysis a theoretical aspect of this work was to prepare some deuterated alkylthiophenes. It was hoped that such compounds would be useful in explaining the mechanism of breakdown in the mass spectrometer. During the mass spectral analysis the bond between the alpha and beta carbon atoms apparently ruptured and an olefin was formed. Spectroscopists are interested in accounting for the olefin formation and consequently are concerned as to which hydrogen migrates in the process. Therefore, another objective of this work was the preparation of a 2-alkylthiophene containing a side chain with deutero labeling on specific carbon atoms. Unfortunately, this phase of the work scarcely progressed beyond the planning stage and further work must be carried out. Finally, it should be pointed out that all the compounds prepared were tested by the Microbiological Research Group at the Texas Woman's University for their biological activity. This was done because it was realized that there was a possibility that some of these compounds might have some definite physiological properties which would be of interest and value to mankind.