On the Catalytic Action of Japanese Acid Earth. XI. The Isomerisation of Aldehydes to Ketones and the Explanation of the Migration of the Radicals from the Standpoint of the Electronic Theory (Continued and concluded)

Abstract

Abstract (1) All the phenomena hitherto ascribed to the characteristic catalytic action of Japanese acid earth can be explained by taking its strong electron-seeking property into consideration. Thus its ability to promote the hydrolysis of cane sugar or starch and the oxidation of pyrogallol and its property to give various oxidase-like colour reactions are all due to its selective adsorptive power for hydroxyl ion. The facts can similarly be explained that the dehydration or deamination of various organic compounds takes place through its catalytic action followed by the intramolecular rearrangement, as observed in the reaction of producing cyclopentane derivatives from cyclohexanol, cyclohexylamine or their methyl derivatives. The initial step of the formation of β,β′-dinaphthyl from naphthalene in the presence of the earth is the polarisation of the naphthalene molecule promoted by its electron-seeking property. (2) Several diarylacetaldehydes have been newly synthesised and found to rearrange themselves to give the corresponding ketones, when heated at 300°C. in the presence of the earth. Thus phenyl p-tolyl and m-tolyl p-tolyl acetaldehydes gave phenyl p-methylbenzyl and m-tolyl p-methylbenzyl ketones respectively, while o-tolyl p-tolyl and p-tolyl p-chlorophenyl acetaldehydes gave the respective mixtures of o-toly p-methylbenzyl and p-tolyl o-methylbenzyl ketones and of p-chlorophenyl p-methylbenzyl and p-tolyl p-chlorobenzyl ketones. (3) By comparing the yields in the isomeric ketones thus produced the order of the facility of separation of the different aryl groups was determined as follows:— Phenyl, m-tolyl>p-chlorophenyl>o-tolyl>p-tolyl. The phenyl group may most probably have the greater migratory tendency than the m-tolyl. (4) The mechanism of the conversion of the aldehydes to the ketones has been discussed. It has been postulated that an electromeric displacement of electrons in the carbonyl group (Remark: Graphics omitted.) is promoted by the action of the earth, and one of the aryl groups migrates with its valency electrons from the adjacent a-carbon atom to the depleted carbonyl carbon. A proton is then splitted from the carbonyl carbon and unites with the carbonyl oxygen to give the enolic form of the ketone, isomeric to the aldehyde. The conclusion has been reached that the more electron-attracting of the two aryl groups must be first separated as anion. (5) It was confirmed that the capacity of the p-tolyl group for electron-release is much larger than those of o-tolyl, m-tolyl, phenyl and p-chlorophenyl groups. By these results a new chemical evidence has been given for the tautomeric effect of the methyl group. (6) Following compounds have been newly synthesised and their constitutions were confirmed:— a-phenyl a-p-tolyl, a-m-tolyl a-p-tolyl, a-o-tolyl a-p-tolyl and a-p-chlorophenyl a-p-tolyl ethylene glycols and their benzoyl derivatives; p-tolyl m-methylbenzyl, m-tolyl p-methylbenzyl, o-tolyl p-methylbenzyl, p-tolyl o-methylbenzyl, p-chlorophenyl p-methyl-benzyl and p-tolyl p-chlorobenzyl ketones and their oximes and semi-carbazones; m-tolyl p-tolyl, o-tolyl p-tolyl and p-tolyl p-chlorophenyl acetic acids; p-methylbenzoyl carbinol, p-chlorobenzoyl methyl acetate and p-chlorobenzoyl carbinol. (7) o-Tolyl p-methylbenzyl and m-tolyl p-methylbenzyl ketones have been found to be oxidised slowly by the action of atmospheric oxygen on long standing, giving the mixtures of o-toluic and p