Mechanism of the meta-Alkylation of Phenol on Condensed Phosphoric Acid-Kieselguhr

• Published in: Chemical & pharmaceutical bulletin Vol. 19; no. 12; pp. 2518 - 2522
• Main Authors: INOUE, MASAMI, ENOMOTO, SABURO
• Format: Journal Article
• Language: English
• Published: Tokyo The Pharmaceutical Society of Japan 01.01.1971; Japan Science and Technology Agency
• ISSN: 0009-2363; 1347-5223
• DOI: 10.1248/cpb.19.2518

The alkylation of phenol to meta position takes place on condensed phosphoric acid-kieselguhr catalysts with C2-C4 olefins or C1-C4 alcohols as alkylating reagents. In our experiments, the yield of the meta isomer was 40%. From the distribution of the isomers of the compound, we deduced that this alkylation reaction takes place via phenylether and ortho alkylphenol consecutively. The mechanism of the reaction was investigated in detail, using radiogaschromatography; the ratio of the intramolecular rearrangement of alkyl group to the intermolecular one was evaluated. Intra- and inter-molecular rearrangements of phenylether to ortho alkylphenols occured in the same extent. On the other hand, for the isomerization of ortho alkylphenol to meta and para position, the intermolecular reaction was estimated to be only 20%. When the number of carbons of the alkyl group increased, the ratio increased. The mechanism of the alkylation is then discussed on the basis of the infrared spectra of phenol and methanol adsorbed on the catalyst at 450°.