Essential oils are soluble in organic solvents extracts. The organic phase from steam distillates from plants or plant parts and gives a strong characteristic of the origin of plant odor. In addition to essential oils Hydrolates as byproducts of steam distillation. They contain the water-soluble components of the distilled plants and also in trace essential oils. Essential oils consist largely of mixtures of different terpenes, sesquiterpenes and aromatic compounds. Terpenes are formally derived from isoprene units. Monoterpenes consist of two sesquiterpenes from three isoprene units. The table below shows some examples of the various molecules that are found in essential oils.
Residues of fat-soluble pesticides in the starting material can also accumulate in the fat-soluble essential oil. Essential oils contain phytochemicals that may serve the plant to attract insects for pollination, keep away pests and to protect against diseases that are caused by bacteria or fungi, for example. Essential oils are composed of many different chemical compounds. They are soluble in fat, but do not contain fats. Unlike fatty oils, essential oils evaporate without leaving a residue. In water, they are only very slightly soluble. At normal pressure, its boiling point is much higher than that of water or superheated steam; however, they are distilled. They usually have a lower density than water and therefore form floating liquid drops on the water surface (one exception is, for example cinnamon).