GB782973A - Ester oils derived from terpenes and a process for their production - Google Patents

Abstract

The invention comprises normally liquid esters of terpane methylol, which has the structural formula <FORM:0782973/IV (a)/1> or the corresponding terpane carboxylic acid and an aliphatic carboxylic acid or aliphatic alcohol respectively, the component in the ester derived from the aliphatic acid or alcohol having at least 2 carbon atoms and preferably being branched when it contains more than 8 carbon atoms. Specified esters are the acetic, propionic, butyric, valeric, and caproic acid esters of terpane methylol. The esters are produced by subjecting terpane methylol or terpane carboxylic acid to esterification with the appropriate acid or alcohol. The terpane methylol or terpane carboxylic acid is obtained by a process comprising reduction or oxidation of the corresponding terpane methylal produced, by the catalytic addition of carbon monoxide and water to dipentene contained in or produced from oil of turpentine. Thus, the whole of oil of turpentine may be subjected to the aldehyde synthesis or narrow fractions rich in dipentene may be used. Preferably, the oil of turpentine or a fraction thereof is treated in known manner for the conversion of dicyclic terpenes, e.g. a -pinene, into dipentene. The aldehyde products may be converted by the action of air or oxygen into carboxylic acids or, with the addition of mild alkali, e.g. sodium carbonate, into carboxylic acid salts from which the carboxylic acids are released by means of a mineral acid; terpane carboxylic acid is then isolated from the product, for example by fractionation. The aldehyde may be catalytically hydrogenated, or subjected to hydrolysing hydrogenation, to form the methylol; terpane methylol is then isolated from the product, for example by fractionation. Terpane methylol may be used as such or it may be converted into the corresponding carboxylic acid by treatment with molten alkali and acidification of the alkali metal salt so formed. The use of straight-chain C2-C8 aliphatic acids or alcohols, or branched-chain acids or alcohols having more than 8 carbon atoms, in the esterification results in esters having pour-points below -20 DEG C., which are useful as clockwork oil or for lubricating ice machines and other apparatus operating at low temperature. If the esterification is effected with long-chain fatty acids, such as stearic acid, ester oils of increased viscosity and flash points above 200 DEG C. are obtained. Suitable aliphatic alcohols may be obtained by the catalytic addition of carbon monoxide and hydrogen to olefines followed by catalytic hydrogenation, and may be isolated or obtained in high concentration by fractional distillation, the branched-chain alcohols being concentrated in the first third or the first four-tenths of the distillate. The aliphatic carboxylic acids may be obtained by oxidation of the aliphatic alcohols obtained in the above manner or may be produced directly from the intermediate aldehydes. Examples describe the esterification of terpane methylol, obtained from oil of turpentine by the oxo synthesis followed by hydrogenation, in the presence of hydrochloric acid as catalyst and benzene or toluene as water entrainer, by refluxing with (1) acetic anhydride, (2) propionic acid, (3) butyric acid, (4) valeric acid or caproic acid, and (5) a C15 fatty acid obtained by treating a branched C15 alcohol with molten alkali. In example (6), a branched C15 alcohol is esterified with terpane carboxylic acid in the presence of toluene and toluene-sulphonic acid. In Example (7) a branched C12 alcohol is esterified with terpane carboxylic acid as in (6); the same C12 alcohol is converted into the C12 fatty acid by treatment with molten alkali followed by acidification, and the acid is esterified with terpane methylol.