Violet and Iris Oil

The characteristic scent of violets comes from their flowers. Violet flower oU contains aroimd 22 % of enantiomericaUy pure (Jl)-a-ionone and jS-ionone, as well as their dihydro derivatives (Fig. 3.14). Their discovery was based upon an inaccurate structure determination. In 1893, Ferdinand Tiemann believed, that with the ionones he had identified the odouriferous principle of iris oil. As became apparent some 50 years later, this consisted however of a mixture of structurally related irones, which are methyl-substituted ionones. 

14 Constituents of violet flower oil. Undiluted, a-ionone smells of cedar wood by dilution with alcohol, the violet fragrance clearly emerges. 

The main constituents of iris oil from Iris pallida are (+)-c s- -irone, (+)-frfl s-a-irone, (+)-)5-irone and (+)-cis-y-irone. Iris germanica contains virtually the same irones, but with predominantly the opposite chirality and to some extent also different enantiomeric purity (-)-cis-a-irone, (+)-trans-a-irone, (-)-)5-irone and (-)-ds-y-irone (Fig. 3.16). 

Iris blitter of Kalian Iris pallida dalmarica  

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