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SUMMARY The terpene and sesquiterpene hydrocarbons in various citrus essential oils are analyzed in a two‐step procedure. During the first step, the oxygen‐containing compounds are removed by column chromatography. In the second step, the terpenoid‐free oil is analyzed by gas chromatography, using a small sample to obtain the terpene analysis and a larger sample to obtain the sesquiterpene analysis. It was found expedient to increase the temperature during the analysis to shorten the sesquiterpene elution time. This method has been applied to different types of orange and grapefruit oils, also to tangerine, lemon, and lime oils. It is now possible to obtain a rapid evaluation of the hydrocarbons in these essential oils. A semi‐quantitative relationship between the hydrocarbons in the individual oils and between various oils can be obtained directly from the chromatograms. The identity of the constituents was determined by infrared and mass spectroseopy, and the wide compositional variations between the oils are discussed.

SUMMARY Nootkatone, an important flavoring constituent in grapefruit, has been synthesized from the sesquiterpene hydrocarbon valencene. Valencene, which is isolated from orange oil, was oxidized with tert‐butyl chromate to yield a sesquiterpene ketone having the same physical properties as the natural nootkatone.

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