Acyl halide

Acyl halide

An acyl halide (also known as an acid halide) is a chemical compound derived from an oxoacid [http://goldbook.iupac.org/A00123.html] by replacing a hydroxyl group with a halide group.GoldBookRef|title=acyl halides|url=http://goldbook.iupac.org/A00124.html]

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. 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, such as chlorine. Acyl chlorides are the most commonly used acyl halides.

The hydroxyl group of a sulfonic acid may also be replaced by a halogen to produce the corresponding sulfonyl halide. In practical terms this is almost always chlorine to create a sulfonyl chloride.

Preparation

A common method for the synthesis of acyl halides in the laboratory is by reaction of carboxylic acids with reagents such as thionyl chloride or phosphorus pentachloride for acyl chlorides, phosphorus pentabromide for acyl bromides and
cyanuric fluoride for acyl fluorides.

Aromatic acyl chlorides can be prepared by chloroformylation, a specific type of Friedel-Crafts acylation using formaldehyde as the reagent.

Reactions

Acyl halides are rather reactive compounds often synthesized to be used as intermediates in the synthesis of other organic compounds. For example, an acyl halide can react with:
*water, to form a carboxylic acid
*an alcohol to form an ester
*an amine to form an amide
*an aromatic compound, using a Lewis acid catalyst such as AlCl3, to form an aromatic ketone. "See" Friedel-Crafts acylation.

In the above reactions, HX (hydrogen halide or hydrohalic acid) is also formed. For example, if the acyl halide is an acyl chloride, HCl (hydrogen chloride or hydrochloric acid) is also formed.

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 (i.e., double chloride) 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 (carbonyl dichloride, Cl–CO–Cl) is a very toxic gas which may be thought of as the dichloride of carbonic acid (HO–CO–OH). 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.

General hazards

Volatile acyl halides are lachrymatory 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. In general, acyl halides (even non-volatile compounds such as tosyl chloride) are irritants to the eyes, skin and mucous membranes.

References


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  • acyl halide — acilhalogenidas statusas T sritis chemija formulė RCOHal atitikmenys: angl. acyl halide rus. ацилгалогенид; галогенангидрид кислоты ryšiai: sinonimas – rūgšties halogenanhidridas …   Chemijos terminų aiškinamasis žodynas

  • acyl halide — noun Any organic compound containing an acyl functional group directly attached to a halogen. See Also: acyl bromide, acyl chloride, acyl fluoride, acyl iodide …   Wiktionary

  • acyl halide — noun organic compounds containing the group COX where X is a halogen atom • Syn: ↑acid halide • Hypernyms: ↑organic compound • Hyponyms: ↑acetyl chloride, ↑ethanoyl chloride …   Useful english dictionary

  • Acyl chloride — In organic chemistry, an acyl chloride (or acid chloride) is an organic compound which is a reactive derivative of a carboxylic acid. As part of its molecular structure, an acyl chloride has the reactive functional group CO Cl. An acyl chloride… …   Wikipedia

  • acyl bromide — noun Any organic compound containing an acyl functional group directly attached to a bromine atom. See Also: acyl halide, acyl chloride, acyl fluoride, acyl iodide …   Wiktionary

  • acyl iodide — noun Any organic compound containing an acyl functional group directly attached to a iodine atom. See Also: acyl halide, acyl bromide, acyl chloride, acyl fluoride …   Wiktionary

  • acyl chloride — noun Any organic compound containing an acyl functional group directly attached to a chlorine atom. See Also: acyl halide, acyl bromide, acyl fluoride, acyl iodide …   Wiktionary

  • acyl fluoride — noun Any organic compound containing an acyl functional group directly attached to a fluorine atom. See Also: acyl halide, acyl bromide, acyl chloride, acyl iodide …   Wiktionary

  • Acyl — group of a carboxylic acid. An acyl group is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid,[1] including inorganic acids. In organic chemistry, the acyl group is usually derived from a carboxylic acid… …   Wikipedia

  • acid halide — noun organic compounds containing the group COX where X is a halogen atom • Syn: ↑acyl halide • Hypernyms: ↑organic compound • Hyponyms: ↑acetyl chloride, ↑ethanoyl chloride * * * noun …   Useful english dictionary

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