Geranyl acetone: Properties, Production process and Uses

Properties of Geranyl acetone

Geranyl acetone, also known as 6,10-dimethyl-5,9-undecadien-2-one; 6,10-dimethyl-5,9- undecadiene-2-one, dihydropseudoionone, α, β-dihydropseudoionone, is a derivative of linalool.The chemical structure is:

Geranyl acetone is a light yellow to colorless, transparent and oily liquid with an aroma of magnolia. Its boiling point is 250°C (101.3 kPa), and the flash point is 101°C. The density is 0.8729 g^.cm^–3 and the refractive index is 1.4674 at 20°C. Geranyl acetone has a (Z)-isomer, neryl acetone or (Z)-geranyl acetone.

Production process of Geranyl acetone

Although the natural geranyl acetone is found in tomatoes, mint and passion fruit, the product is industrially produced by chemical synthesis. The chemically synthesized product is a mixture of (Z)- and (E)-isomers. The (Z)-isomer is called neryl acetone and the (E)-isomer is called geranyl acetone. There are three routes for manufacture of geranyl acetone: the first one is that myrcene reacts with methyl acetoacetate in the presence of a precious metal catalyst and subsequently the intermediate is subjected to hydrolysis and decarboxylation to obtain geranyl acetone. However, the catalyst used in the reaction process is very expensive, which is not conducive to industrialization. The second synthesis route is that myrcene and hydrogen chloride undergo an addition reaction to obtain geranyl chloride and its isomers, and then the as-prepared chlorides react with ethyl acetoacetate followed by hydrolysis and decarboxylation to generate geranyl acetone. Although the use of precious metal catalysts can be avoided, a large amount of wastewater is generated in the second synthesis route. The third synthesis route is that geranyl acetone is directly prepared by the Carroll reaction using linalool and ethyl acetoacetate as raw materials. Currently, the third route is widely used, and the commonly used catalysts are aluminum alkyl, aluminum isopropoxide, sodium ethoxide, sodium dihydrogen phosphate, disodium hydrogen phosphate and the like. The reaction equation is as follows:

For example, using sodium dihydrogen phosphate as the catalyst, the reaction was carried out at 170°C for 8h, with a catalyst dosage of 3% based on the mass of linalool and a molar ratio of linalool to ethyl acetoacetate of 1:2, resulting in a total yield of geranylacetone and nerylacetone up to 97.5%. The ratio of geranylacetone to nerylacetone is approximately 6:4.

Uses of Geranyl acetone

Geranyl acetone is a fragrance and flavor substance, which is widely used in foods, beverages, cosmetics, household cleaners and detergents. It can be used to formulate a variety of flavors such as apple, banana and citrus essence. When used in the preparation of citrus essence, it can effectively prevent the bitter and astringent taste of real citrus. Geranyl acetone can be used in both rose-flavored flavors as an auxiliary flavor in non-flora. The combination of geranyl acetone and lavender and fruity is very effective, which can play the role of refreshing and natural aroma and make the floral fragrance more mellow. In addition, geranyl acetone is also used in the cigarette industry to enhance the coordination of smoke aroma.

Geranyl acetone is a key intermediate for the synthesis of dehydronerolidol and farnesol and is also a key intermediate in the production of isophytol. Isophytol is an important side chain of synthetic vitamin E, and an increase in the demand for vitamin E is bound to expand the production of geranyl acetone.