Essais de réactions dissymétriques sur quartz optiquement actif

Abstract

AbstractI. Three catalytical reactions are investigated (hydrogenation of methylethylketone, dehydrogenation and dehydration of 2‐butanol) the catalyst being optically active quartz, either pure or metal covered. Emphasis is laid upon the most appropriate experimental conditions, generally neglected heretofore, when stereospecificity may be expected in a catalytic heterogeneous reaction. Numerous attempts under carefully controlled conditions have always led to negative results. Apparent optical rotations sometimes observed are shown to result from an extraneous effect due to minute quartz particles carried away with the reaction products.II. Attempts to separate at room temperature various racemic modifications (2‐butanol, cobalt or chromium complexes, ammonium tartrate) by liquid‐solid chromatography on optically active quartz have always led to negative results. The resolution of (±)‐2‐butanol at dry ice temperature was also unsuccessful.III. The failure to observe any asymmetric effect in catalysis as well as in adsorption on optically active quartz prompts to a critical analysis of previous work where small but positive effects have been claimed. It is shown that most of the small rotatory powers observed are within the limit of error of the measurements and that a number of results are inconsistent or unlike. These may have been vitiated by an extraneous effect which has been recognised and had been overlooked previously (dichroism or double refraction due to minute quartz particles suspended in the observed liquid).