| 摘要 |
Diaryl paraffins are prepared by condensing an aryl compound having at least one replaceable hydrogen attached to the aromatic nucleus with a saturated aliphatic aldehyde of at least 2 carbon atoms in the presence of hydrogen fluoride as catalyst. Aryl hydrocarbons and their hydroxy, chlorine, bromine or fluorine substituents may be used, also halogenated aldehydes. Hydrocarbons having nuclear methyl substituents, e.g. toluene and xylenes, are the most reactive. Others specified are benzene, naphthalene, diphenyl and ethyl xylenes. Aldehydes include acetone, acetaldehyde, propionaldehyde, butyraldehyde, n-valeraldehyde, trimethyl-acetaldehyde, heptaldehyde and dichlor-, dibrom-, trichlor- and tribrom-acetaldehyde and butyl chloral. Those of 8 carbon atoms or less are preferred. The amount of aldehyde should not be more than 60, and preferably 50 per cent or less of the theoretical, especially when mixtures of hydrocarbons, such as m- and p-xylenes, are treated to react one, for example m-xylene, preferentially. Temperatures for acetaldehydes are about - 20 DEG to 65 DEG C. or higher, preferably about 0 DEG C., until the initial condensation has taken place, when an increase to 65 DEG C. may be permitted. The weight ratio of HF to acetaldehyde is generally 1.4-5 : 1 when using the more reactive aromatics, but for diphenyl and chlor-aryl compounds may reach 50 : 1. Inert solvents such as chlorinated hydrocarbons may be employed, for example when solid aromatic compounds are reacted. Chlor-aromatics such as chlorbenzene may be used owing to their low reactivity as compared to the hydrocarbons. Superatmospheric pressures may be used to prevent volatilization of the reactants and catalyst. Pure asymmetric diaryl ethanes such as di-(p-tolyl, o-xylyl, and m-xylyl)-ethanes, and 2-, 5-, 21-, 51-tetramethyl diphenyl ethane prepared by the process yield pure styrenes by the processes of Specifications 569,465, 592,867 and 598,069. The diaryl paraffins are also used for insecticides and electrical insulating media. Examples describe the condensation of toluol, xylenes, naphthalene, dissolved in chlorbenzene, and diphenyl, in chloroform, with paraldehyde. Using mixtures of m- and p-xylene, the former only is reacted, and the residual xylene enriched in the p-isomer is further reacted, in one case after first cooling to separate pure p-xylene which may itself be subjected to the condensation. Samples are furnished of dihydroxy diphenyl ethane prepared from phenol and paraldehyde, and ditolyl butane from toluene and butyraldehyde. The Specification as open to inspection under Sect. 91 comprises the use of any saturated aliphatic compound having a carbonyl group, acetone, methyl ethyl and methyl hexyl ketones being specified. This subject-matter does not appear in the Specification as accepted.
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