GB189823254A - Manufacture of Ionone from Citral and Acetone and of Cyclocitral as Intermediate Product. - Google Patents

Abstract

23,254. Strebel, A. Nov. 4. Perfumery.-Ionone is prepared from citral and acetone by the following operations :-(1) Cyclocitral is first produced. For this purpose citral is condensed with cyanacetic acid, or a salt or ether thereof, in the presence of caustic soda' and alcohol, whereby citralidene cyanacetic acid melting at 124‹-122‹ C., or a derivative thereof, is produced ; then this product is converted into its cyclic isomeride by boiling it at a reflux-cooler with diluted sulphuric acid for twelve hours, after the manner described in Specification No. 22,114, A.D. 1893; and, finally, the cyclic compound, which after removal of bye-products is obtained as a syrup, is distilled in a powerful current of steam in presence of caustic alkali, and the distillate is fractionated to obtain crude cyclocitral as a yellowish liquid boiling at 80‹-110‹ C. under a pressure of 15 mm. The cyclocitralidene cyanacetio acid may also be hydrolysed by boiling it with caustic potash solution and xylene, and then separating and fractionating the xylene layer. A small quantity of a gentle oxidizing- agent, such as lead peroxide or the like, may advantageously be used in these hydrolysing operations. (2) Cyclocitral is condensed with acetone by means of alkaline reagents, for example, a solution of sodium in alcohol, at the ordinary temperature. The mixture is then neutralized by tartaric or other acid, and is distilled in a strong current of steam. On redistillation the fraction which boils at 130‹-140‹ C., under a pressure of 16 mm., is collected as ionone. It is rich in #-ionone, and yields a semi-earbazone melting at 148‹ C., and a p-bromophenyl-hydrazone melting at 116‹ C.