Method for the preparation of tertiary-alkyl-phenols

摘要

Tertiary-alkyl-phenols are prepared by reacting an iso-olefin with a phenol having a hydrogen atom ortho and/or para to the hydroxyl group and consisting of a hydroxylated aromatic hydrocarbon or a hydroxylated monohalo-aromatic hydrocarbon, in the presence of from 0.01 to 0.02 per cent of an iron chloride and from 0.075 per cent to 0.25 per cent of hydrogen chloride or hydrogen bromide, based on the weight of phenol. The iso-olefins are defined as olefins of formula wherein each R is a saturated aliphatic hydrocarbon radical and R1 may be such a radical or hydrogen. Preferably 1 mol. of olefin is reacted with 1.5 to 3 mols. of phenol. The reaction may be carried out by stirring the iron chloride and hydrogen chloride or bromide in the molten phenol (phenols which are solid at operating temperatures may be dissolved in an inert solvent) heating the mixture to between 55 DEG and 150 DEG C. and adding the iso-olefin slowly with continued agitation, heating further to complete the reaction, cooling, neutralizing and fractionally distilling to separate the tertiary-alkylphenol. The process described gives largely the para-isomer if the para-position is open for substitution, otherwise the ortho-isomer is formed. Specified phenols are phenol, cresols, thymol, p-tert.-butylphenol, o-chlorophenol, 4-bromo - 2 - methyl - 5 - isopropylphenol, catechol, resorcinol, pyrogallol, a -naphthol, 1-chloro-2-naphthol, o- and p-phenylphenol, and a -anthrol. Specified olefins are isobutylene, 2-methyl-1- or -2-butene, 3-methyl-2-pentene, 4-methyl- or -ethyl-3-hexene, 3-methyl-2-hexene, 2-ethyl-1-hexene and diisobutylene. In examples: (1) phenol (2 mols.) and isobutylene (1 mol.) were reacted as described above using ferric chloride and hydrogen chloride as catalysts and p-tert.-butylphenol obtained; (2) the following phenols and olefins were reacted as in (1), isobutylene and o-chlorophenol or o-cresol or o-phenylphenol or m-cresol and 2-methyl-2-methyl-2-butene or diisobutylene and phenol; (3) comparative reactions using isobutylene and phenol were carried out replacing the iron chloride with aluminium chloride ot using hydrogen chloride or ferric chloride alone.