FATTY ACID CARBONATES
Carbonates (esters of carbonic acid, H2CO3) are well known to chemists as they represent an important class of organic compounds and among them oleochemical carbonates have interesting characteristics which make them candidates for many industrial applications.
The most common carbonates have the following structure : RO-CO-OR
R is a linear chain with 8 to 18 carbon atoms, saturated or with one double bond (dioleyl carbonate), or a branched chain (ethylhexyl, butyloctyl or hexyldecyl).
They are miscible in organic solvents but insoluble in water. Unsaturation or branching on the alkyl chain lowers their melting point (Kenar JA, Inform 2004, 15, 580).
The condensation of phosgene (ClCOCl) with an alcohol appears the most commonly used procedure to synthesize oleochemical carbonates.
The polar nature of the carbonate moiety enables it to adhere strongly to metal surfaces. Thus, they are used as lubricant components which have a protective property for metal corrosion. Some C8 to C18 carbonates have been exploited in personal-care products (sunscreen, cosmetics), dioctyl carbonate being also used as emollient or solvent in UV-filter solutions.
Extraction of metal ions (gold, silver, platinum) is improved by the use of the chelating properties of oleochemical carbonates when mixed with the metal-containing aqueous phase. Future developments will ensure a growing interest in these molecules.