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. Acyl halide compounds are used as an intermediate
for agrochemicals and pharmaceuticals, dyes, and peroxide compounds as well as
textile auxiliaries, emulsifiers. |
Cyclohexane is the six-membered alicyclic
hydrocarbon consisting of six carbon atoms linked to each other to form a ring,
with each carbon atom bearing two hydrogen atoms, C6H12. A cyclic compound is an
organic compound that contains one or more closed rings of carbon atoms. The
term alicyclic refers to cyclic compound that behaves chemically like aliphatic
compounds (open-chain), which means the exclusion of carbocyclic compounds of
aromatic rings with an array of π-electrons characteristic. Cyclohexane is a
colorless, highly flammable, mobile liquid with a pungent odor. It is insoluble
in water and soluble in alcohol, ether, and almost organic solvents. Cyclohexane
is a non-corrosive and quick volatilize liquid and sublimes between -5 to 5 C.
Cyclohexane can exist in a number of interconvertible three-dimensional
conformations, the two simplest being are the chair and boat conformation and
others include the half-chair and twist-chair conformation. Cyclohexane can
cause irritation to the eyes and mucous membranes in workers. Repeated and
prolonged contact with skin may cause dermatitis. The substance has not been
shown to cause the hematologic changes associated with exposure to benzene.
Cyclohexane occurs naturally in crude oils. Some cyclohexane is recovered from
petroleum streams by fractionation. The bulky commercial production of
cyclohexane is based on hydrogenation of benzene in closed system. Cyclohexane
consumption is linked almost entirely to nylon production. Nylon is further
processed into fibers for applications in carpeting, automobile tire cord,
clothing, and other growing industrial fields. Cyclohexane is used as a solvent,
oil extractant, paint and varnish remover, dry cleaning material, and in solid
fuels. It has been used as a insecticide itself. Cyclohexane is used as a
chemical intermediate to produce target molecules. Natural compounds of one to
five alicyclic rings with great variety and complexity are found particularly in
steroids and terpenes. Cyclohexane structure, six membered-ring, is one of the
major skeleton in nature. Cyclohexane derivatives can be used for the synthesis
of pharmaceuticals, dyes, herbicides, plant growth regulator, plasticizers,
rubber chemicals, cycloamines and other organic compounds. |