Perfume Ingredients Derived from Aliphatic Materials

PERFUME INGREDIENTS DERIVED FROM ALIPHATIC MATERIALS 

The aliphatic fragrance materials of natural origin are mostly derived from fatty acids and related materials. As a result of their biosynthetic pathway (see Chapter 3), those formed directly all have an even number of carbon atoms in the chain. Any with an odd number of carbons in the chain are likely to be breakdown products. Fatty acids are useful precursors for aliphatic fragrance materials, but the same observations about the number of carbon atoms in the chain, of course, also apply. Thus, for example, octanal can be prepared by oxidation of octanol, which can be obtained from coconut oil. Similarly, materials with 10-, 12- or 14-carbon chains can be obtained from other fats. One example of a fatty acid being used in fragrance is myristic acid, the isopropyl ester of which is employed as a solvent. Once a fatty acid or alcohol is available, appropriate oxidation and reduction reactions open routes to 

Synthetic precursors for aliphatic materials mirror the pattern of their naturally derived counterparts in that the commonest units are even in carbon chain length. This is because they are usually derived from ethylene through oligomerisation. Thus, coupling of two ethylene molecules produces a four-carbon chain, three produces six, and so on. In order to obtain an odd number of carbon atoms in the chain, one of the simplest techniques is to add a single carbon to an even chain which can be achieved, for example, by hydroformylation. Hydroformylation also introduces an alcohol function and opens the way for oxidation to aldehydes and acids. Three carbon units are available from propylene as well as by reaction of ethylene with a one-carbon unit. 

The Prins reaction, the acid-catalysed addition of an aldehyde or ketone to a double bond, is a useful reaction in perfumery chemistry and a number of aliphatic fragrance ingredients are prepared in this 

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PERFUME INGREDIENTS DERIVED FROM ALIPHATIC MATERIALS... 

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