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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 X is a halogen atom
(fluorine, chlorine, bromine, iodine, and astatine) and R may be aliphatic, alicyclic, aromatic,
and H etc.
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. Benzoyl
Chloride belongs to acyl halides. Acyl halides are
involved in acetylation
process
which introduce an acetyl group (CH3CO-)
into compounds. Benzoyl
Chloride decomposes violently by heating
or on exposure to moist air or water.
It reacts violently
with strong oxidants, metals (especially
iron), alkali and earth alkali metals,
bases and wide range of organic substances such
as amines, dimethyl sulfoxide
and alcohols. The reactions cause
fire and explosion hazard. It is
used to introduce benzenecarbonyl
groups into compounds. Typical
reactions undergone by benzoyl chloride are the Schotten-Baumman
reaction (the benzoylation of compounds containing a
hydrogen), and the Friedel-Crafts reactions (preparation
of substituted benzophenones). It is used in
manufacturing peroxides such as a benzoyl
peroxide and t-butyl perbenzoate. It
is also used in the synthesis of benzophenone
and its derivatives used in manufacturing
pesticides, pharmaceuticals, perfume
fixative, polymerization catalyst, benzolating
agents, and dyestuffs. n-Butyryl
Chloride, C-4 Acyl halide, is a colorless
to light yellow liquid with a strong pungent
odor; decomposes in water; soluble in almost
aprotic organic solvents. It is used as an intermediate for
organic synthesis for the preparation of pharmaceuticals, agrochemicals,
dyes, cellulose esters, and peroxide compounds. |
