GB706176A - Manufacture of aldehydes - Google Patents

Abstract

Substituted glutardialdehydes having the formula:- <FORM:0706176/IV (a)/1> Wherein R is an alkyl or alkenyl radical of up to four carbon atoms may be used as starting materials in plastic condensation products, for example with amines. The substituted aldehydes may be obtained by condensing alphamethacrolein with a primary alcohol (ROH) in the presence of an alkaline condensing agent (see Group IV (b)).ALSO:Substituted glutardialdehydes of the general formula:- <FORM:0706176/IV (b)/1> wherein R is an alkyl or alkenyl radical of up to four carbon atoms, are obtained by reacting alpha-methacrolein with a corresponding primary aliphatic alcohol (ROH) in an amount which is in stoichiometrical excess over the amount of alpha-methacrolein in the presence in the reaction mixture of an alkaline condensing agent and at a temperature between 0 and 50 DEG C., terminating the reaction by the addition of an amount of acid at least sufficient to neutralize said alkaline agent before substantial amounts of higher polymers have been formed and isolating the substituted glutardialdehyde thus produced from the reaction mixture by distillation. The invention also comprises as new compounds 2-allyloxymethyl-2:4-dimethylpentanedial and 2-n-butoxymethyl-2:4-dimethylpentanedial. The acid used to neutralize the alkaline condensing agent should be a weak acid, preferably an organic acid such as acetic acid. Specified alcohols (ROH) are methyl, ethyl, n-propyl, n-butyl and allyl alcohols. Suitable alkaline condensing agents are inorganic bases such as the hydroxides of the alkali metals and the oxides or hydroxides of alkaline earth metals, or organic basic compounds such as alkyl or aryl amines and quatenary ammonium hydroxides. The alkali is preferably applied in the form of a solution or suspension in water or alcohol. Alkali metal alcoholates in alcoholic solution may also be used, the alcoholates being preferably those of the alcohols employed in the reaction. It is preferred to use less than 1 per cent, by weight of alkaline condensing agent based on the methacrolein present. It is especially advantageous to effect the condensation in a mixture which contains more than 2 per cent. but less than 75 per cent. by weight of water based on the total reaction mixture. Small quantities of a polymerization inhibitor such as hydroquinone or pyrogallol may be added to the methacrolein before use in the process. On completion of the condensation by the addition of acid the reaction mixture is distilled whereby unreacted alcohol and unchanged methacrolein are recovered and the residual liquid is then fractionated preferably under reduced pressure to recover the substituted glutardialdehyde. By catalytic hydrogenation of the products, preferably under pressure and at elevated temperature, 2-alkoxymethyl-2, 4-dimethylpentanediols are obtained. The dialdehydes may also be converted to the corresponding acids which may be esterified. Examples describe the production of (1) 2-methoxymethyl-2:4-dimethylpentane dial by condensing alpha - methacrolein and methanol in the presence of aqueous sodium hydroxide solution using various amounts of water, some betamethoxyisobutyraldehyde being obtained as by-product, and also by using an aqueous solution of barium hydroxide octahydrate as condensing agent; (2) 2-ethoxymethyl-2:4-dimethylpentane dial (some beta-ethoxyisobutyraldehyde being obtained as by-product) from alpha-methacrolein and ethanol in the presence of aqueous sodium hydroxide solution; (3) and (4): 2-allyloxymethyl-2:4-dimethylpentane dial and 2-n-butoxymethyl-2:4-dimethylpentane dial from alpha-methacrolein and allyl alcohol or n-butanol respectively in the presence of aqueous sodium hydroxide solution. In each case the condensation is terminated by the addition of acetic acid. U.S.A. Specification 2,212,894 is referred to.