Lavender, fenchone

Another type of lavender, Lavandula stoechas, is less commonly encountered. It has a very high camphor content (15-30%), which necessitates cautious handling. Its main component is fenchone (45-50%), a terpenoid ketone, which, although a ketone, is considered nontoxic, nonirritant and nonsensitizing. 

Fenchone is a pleasant-smelling terpene isolated from oil of lavender. Propose a pathway for the formation of a-fenchone from geranyl pyrophosphate. Hint A car-bocation rearrangement is required.)... 

Fenchone (254) occurs in a number of essential oils, such as cedar leaf and lavender, and the (—)-isomer is particularly important in fennel. Synthetic material is made from pinene. Addition of carboxylic acids to a-pinene gives the corresponding esters of fenchol. These esters can be hydrolyzed to fenchol, which is then oxidized to fenchone. It is used mainly in reconstitution of fennel oils. 

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