GB697905A - Tetrahydrobenzaldehyde acetals - Google Patents

Abstract

The invention comprises the dimethyl and diethyl acetals of D 3-tetrahydrobenzaldehyde, and the manufacture of these and other acetals by reacting an aldehyde of the general formula <FORM:0697905/IV (b)/1> (wherein R1, R2, R3, R4, R5 and R6 represent hydrogen or alkyl or aryl radicals or two of them form a bridge grouping) with a saturated aliphatic monohydric alcohol in the presence of an acetalization catalyst (e.g. a strong mineral or organic acid) under substantially anhydrous conditions, preferably at room temperature or below. Preferred starting materials are those in which R1, R3, R4 and R6 represent hydrogen and either R5 represents hydrogen and R2 a lower alkyl or mononuclear aryl radical or R2 and R5 jointly represent a bridge grouping, e.g. -CH2-. The reaction may be effected by dissolving the aldehyde in the alcohol, adding the catalyst (advantageously also dissolved in the alcohol) while cooling to 16-20 DEG C. or below, and allowing the mixture to stand. In examples, D 3-tetrahydrobenzaldehyde is reacted with: (1) ethyl alcohol in the presence of hydrogen chloride; (2) ethyl alcohol in the presence of sulphuric acid; (3) methyl alcohol as in (1). Additional starting materials specified are 5-methyl-, 2 : 5- and 3 : 4-dimethyl-, 2 : 2 : 5 : 5-tetramethyl-, 2-phenyl-, 2 : 5-endomethylene-and 2 : 5-endoethylene- D 3-tetrahydrobenzaldehyde, and the condensation products of acrolein with 2-methyl- and 1 : 1-dimethylbutadiene.ALSO:A frothing agents in the froth flotation of minerals may be employed acetals of the general formula <FORM:0697905/II/1> wherein R1, R2, R3, R4, R5 and R6 represent hydrogen or alkyl or aryl radicals or two of them form a bridge grouping, and R7 represents an alkyl radical.