acid, phenylacrylic acid, is a fragrant acid occurring in aromatic resins. Cinnamic acid
and Its derivatives are used as as important components in
flavours, perfumes, synthetic indigo and pharmaceuticals.
Acyl is a
radical formed from an organic acid by removal of a hydroxyl group. The general
formula of acyl compound is RCO-. Acyl halide is one of a large group of organic
substances containing the halocarbonyl group, have the general formula RCO·X,
where R may be aliphatic, alicyclic, or aromatic and halide is any compound of
halogens (fluorine, chlorine, bromine, iodine, and astatine) with another
elements and groups. In substitutive chemical nomenclature, their names are
formed by adding '-oyl' as a suffix to the name of the parent compound; ethanoyl
chloride, CH3COCl, is an example.
The terms acyl and aroyl halides refer to aliphatic or aromatic derivatives,
respectively. Acyl halides are made by replacing the -OH group in carboxylic
acids by halogen using halogenating agents. They react readily with water,
alcohols, and amines and are widely used in organic synthetic process whereby
the acyl group is incorporated into the target molecules by substitution of
addition-elimination sequence called acylation reaction. Acylation reaction
involves substitution by an electron donor (nucleophile) at the electrophilic
carbonyl group (C=O). Common nucleophiles in the acylation reaction are
aliphatic and aromatic alcohols, both of which give rise to esters and amines
(RNH2) which give amides.
The carboxylic acid (X = OH) itself can function as an acylating agent when it
is protonated by a strong acid catalyst as in the direct esterification of an
alcohol. Two common acylation agents, with the general formula RCOX, are acid
halides (X = halogen atom) and anhydrides (X = OCOR). Schotten-Baumann reaction
is an acylation reaction that uses an acid chloride in the presence of dilute
alkali to acylate the hydroxyl and amino group of organic compounds. There are
also other acylating agents.