Eugenol, thymol, and carvacrol are important phenols found in volatile oils. Eugenol occurs in Clove oil, Myrcia oil, and other oils; thymol and carvacrol occur in Thyme oil, Ajowan oil, and creosol; and guaiacol are present in creosote and pine tar. 

Alcohols found in volatile oils are classified as: (1) acyclic alcohols, (2) monocyclic alcohols, and (3) dicyclic alcohols. Methyl, ethyl, isobutyl, isoamyl, hexyl, and the higher aliphatic alcohols occur in volatile oils. They are soluble in water, hence, they are washed away in the process of steam distillation. 

The most common esters are of terpineol, borneol and geraniol. The perfumes are aged to undergo esterification, thus improving bouquet. Allyl isothiocyanate in mustard oil and methyl salicylate in wintergreen oil are also esters. The drugs are Lavender oil, dwarf pine needle oil, Mustard oil and Gaultheria oil, Garlic, Valerian, and Rosemary oil.

Hydrocarbons are present in all volatile oils. Limonene is the most widely distributed of the monocyclic terpenes. It occurs in Citrus, Mint, Myristica, Caraway, Thyme, Cardamom, Coriander, and many other oils. Hydrocarbons are present in all volatile oils. 

Cineole (eucalyptol) is found in Eucalyptus, Cajuput, and other volatile oil-yielding drugs. The presence of limonene-l,2-epoxide, pinene oxides, ascaridole (chenopodium oil), and ascaridole epoxide is also reported. 

Aldehydes present in volatile oils are divided into acyclic and cyclic. The acyclic aldehydes are citral, which is a 3:1 mixture of geranial to neral, and citronellal, the aldehyde corresponding to citronellol. The cyclic aldehydes are safranal, phellandral, photocitral A, and myrtenal.