An organic compound formed when an acid and an alcohol combine and release water. Esters formed from carboxylic acids are the most common, and have the general formula RCOOR, where R and R are organic radicals. Esters formed from simple hydrocarbon groups are colorless, volatile liquids with pleasant aromas and create the fragrances and flavors of many flowers and fruits. They are also used as food flavorings. Larger esters, formed from long-chain carboxylic acids, commonly occur as animal and vegetable fats, oils, and waxes. Esters have a wide range of uses in industry. Esters with low molecular weights, such as ethyl acetate, are usually volatile fragrant liquids; fats are solid esters.
Esters encompass a large family of organic compounds with broad applications in medicine, biology, chemistry and industry. Esters are to carboxilic acids and alcohol, what table salt is to hydrochloric acid and sodium hydroxide. They are the organic salts formed when a carboxilic acid exchanges the loosely held hydrogen ion on its carboxyl group, for the alkyl group of a reacting alcohol. In spite of the parallel between the salts and esters, esters do not dissociate in solution into anion/cation pairs as inorganic salt tend to do.
Esters are widespread in nature. They occur both in plants and in animals. Small esters, in combination with other volatile compounds, produce the pleasant aroma of fruits. Many chemicals in combination are responsible for specific fruity fragrances; however, often a single compound plays the leading role. For example, pineapple flavouring contains more than twenty ingredients but ethyl butyrate is the major component that accounts for what we think of as the pineapple-like aroma and flavor.
Esters are ubiquitous. Many naturally occurring fats and oils are the fatty acid esters of glycerol. Esters with low molecular weight are commonly used as fragrances and found in essential oils and pheromones. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties, while polyesters are important plastics, with monomers linked by ester moieties.
Some esters play an important role in insect communication. Isoamyl acetate, the main component of banana aroma, is also the alarm pheromone of the honeybee. (Z)-6-dodecen-4-olide, a circular ester, is the "social scent" of the black-tailed deer. Circular esters (called lactones) are also found in the oily poisonous secretion of termites.
Esters also have remarkable applications in everyday life. Plexiglas is a stiff, transparent plastic made of long chains of esters. Dacron, a fiber used for fabrics, is a polyester which means many esters.
Jojoba esters are the hydrogenation or interesterification product of Jojoba oil. Interesterified Jojoba Esters are commonly used in cosmetic formulations as an emollient, due to its remarkable similarity to the natural oils produced by the human skin, and its high oxidative stability. Fully hydrogenated jojoba esters are most often small beads used to exfoliate the skin.
Jojoba esters are proper waxes; there is no triglyceride component of jojoba esters. Chemically, jojoba esters are a complex mixture of long chain (C36-C46) fatty acids and fatty alcohols joined by an ester bond. Jojoba esters are produced by the interesterification of jojoba oil, hydrogenated jojoba oil, or a mixture of the two. Pure jojoba oil and pure hydrogenated jojoba oil are also correctly described as jojoba esters. The CTFA does not regard partially-hydrogenated jojoba oil as jojoba esters. For this reason, jojoba esters must not contain any trans-unsaturation. Jojoba esters' chemical structure is very similar to that of human sebum and of whale oil.
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