Acyl halide
In
chemistry, the term acyl halide refers to a compound derived from an acid by replacing a hydroxyl group with a halide group.
If the acid is a
carboxylic acid, the compound contains a -COX
functional group, which consists of a
carbonyl group singly bonded to a
halogen atom such as chlorine. The general formula for such an acyl halide can be written RCOX, where R may be, for example, an
alkyl group, CO is the carbonyl group, and X represents the halogen atom. See simple diagram at right.
The RCO- group in an acyl halide can be thought of as an acyl group and the -X radical as the halide part of the molecule; for example, -Cl is chloride.
Encyclopedia
In
chemistry, the term
acyl halide refers to a compound derived from an acid by replacing a hydroxyl group with a halide group.
If the acid is a
carboxylic acid, the compound contains a
-COX functional group, which consists of a
carbonyl group singly bonded to a
halogen atom such as chlorine. The general formula for such an acyl halide can be written
RCOX, where R may be, for example, an
alkyl group, CO is the carbonyl group, and X represents the halogen atom. See simple diagram at right.
The
RCO- group in an acyl halide can be thought of as an acyl group and the -X radical as the halide part of the molecule; for example, -Cl is chloride.
Acyl chlorides are the most commonly used acyl halides. Acyl halides are commonly made by halogenating a carboxylic acid, hence the name
acid halide.
An example of an acyl halide is
acetyl chloride CH
3COCl. See simple diagram at right.
Another example is replacing hydroxyl by chloride in a
sulfonic acid to create a
sulfonyl chloride.
Acyl halide synthesis
A common method for the synthesis of acyl halides in the laboratory is by reaction of
carboxylic acids with reagents such as
thionyl chloride and
phosphorus pentachloride for acyl halides,
phosphorus tribromide for acyl bromides and
cyanuric fluoride for acyl fluorides
Acyl halide reactions
Acyl halides are artificial , rather reactive compounds often synthesized to be used as intermediates in the synthesis of other organic compounds. For example, an acyl halide can
chemically react with:
...
In the above reactions, HX is also formed. For example, if the acyl halide is an acyl chloride, HCl is also formed.
Because acyl halides are rather reactive compounds, they have
toxicity and special precautions should be taken handling them. They are lachrymatory chemicals because they can react with water at the surface of the eye producing hydrohalic and organic acids irritating to the eye. Similar problems can result if one inhales acyl halide vapors.
Multiple functional groups
A molecule can have more than one acyl halide functional group. For example, "adipoyl dichloride", usually simply called
adipoyl chloride, has two acyl chloride
functional groups; see the structure at right. It is the dichloride of the 6-carbon dicarboxylic acid
adipic acid. An important use of adipoyl chloride is polymerization with an organic di-amino compound to form a polyamide called
nylon or polymerization with certain other organic compounds to form
polyesters.
Phosgene is a very toxic gas which may be thought of as the dichloride of
carbonic acid . Both chloride radicals in phosgene can undergo reactions analogous to the preceding reactions of acyl halides. Phosgene is used a reactant in the production of
polycarbonate polymers, among other industrial applications.
See also
External link
