I. Rhenium heptaselenide as a hydrogenation catalyst ; II. Preparation and stereoisomerism of the decahydroquinoxalines
Following the first liquid phase hydrogenation in the early part of the twentieth century, it was quickly recognized that catalytic reductions were convenient research and industrial tools. Through catalytic hydrogenations unsaturated compounds can be saturated, aldehydes transformed into alcohols, nitro groups changed into amines in one step and usually with nearly quantitative yields to mention only a few possibilities. The improvement of existing catalysts and the search for new catalytic materials has been an important phase of catalytic hydrogenation research. A good hydrogenation catalyst should be active toward a variety of substrates at relatively low temperatures, be selective in its action toward different functional groups, and should be resistant to "poisoning." However, one of the greatest deterring factors facing the research chemist as well as the industrial chemist in hydrogenations of organic compounds is the ease wit h which the ordinary active catalysts are poisoned. This poisoning, by a rather large variety of compounds, decreases the efficiency of the catalyst, even to a point where it becomes entirely inoperative. One method, in common use, of circumventing this problem is by the use of catalysts which are not affected by the presence of foreign substances. Two such catalysts that are in common use are molybdenum trisulfide and cobalt polysulfide. This resistance to poisoning is achieved at the expense of a marked decrease in the catalytic activity of these sulfide catalysts as compared to the more active and more easily poisoned platinum (Adams catalyst) or nickel (Raney nickel). From its position in the periodic table and from its electronic configuration the element rhenium (element number 75) and possibly some of its compounds, might well be expected to exhibit catalytic activity. Previous investigations have found this to be the case. Among other compounds and preparations of rhenium, rhenium heptasulfide has been found to be resistant to poisoning yet much more active than either molybdenum trisulfide or cobalt polysulfide. The purpose of this investigation was to establish the catalytic activity of other rhenium compounds, and in particular to investigate the activity of a compound closely related to rhenium heptasulfide, viz., rhenium heptaselenide. This evaluation was done by preparing rhenium heptaselenide and establishing the fact that it has catalytic activity. Once this was done attention was directed toward determining the method of preparation that would yield the most active catalyst. The next step was the trial of the catalyst with a variety of substrates; comparing the ease of reducibility of different functional groups and structural features. Having once extablished the catalytic powers of rhenium heptaselenide, attention was then turned toward an investigation of the poison resistance of the new catalyst. When these things were known a comparison and critical evaluation of rhenium heptaselenide as compared to Raney nickel, Adams' Catalyst, rhenium heptasulfide, molybdenum trisulfide and cobalt polysulfide were made.
College and Department
Chemistry and Biochemistry
BYU ScholarsArchive Citation
Whittle, Charles W., "I. Rhenium heptaselenide as a hydrogenation catalyst ; II. Preparation and stereoisomerism of the decahydroquinoxalines" (1956). Theses and Dissertations. 8383.