ACID CHLORIDES

ACID CHLORIDE (ACYL CHLORIDE) In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group –COCl. i.e O ǁ R– C – Cl Functional group

NOMENCLATURE When naming acid chloride the first step is to select the longest chain containing maximum number of carbon atoms. If you have something substituted into the hydrocarbon chain, the carbon in the -COCl group counts as the number 1 carbon. The “e” of alkanes is replaced by the suffix “OYL” and then chloride is added to it. Ethane becomes Ethanoyl chloride Propane becomes Propanoyl acid.

Name the following compound.

Synthesis From Phosphorus pentachloride PCl5: Phosphorus(V) chloride reacts with carboxylic acids to give steamy acidic fumes of hydrogen chloride and a liquid mixture of the acyl chloride and a phosphorus compound, phosphorus trichloride oxide (phosphorus oxychloride) - POCl3.The acyl chloride can be separated by fractional distillation. From Thionyl dichloride: Sulphur dichloride oxide (thionyl chloride) reacts with carboxylic acids to produce an acyl chloride, sulphur dioxide and hydrogen chloride gases are given off.

PHYSICAL PROPERTIES Acyl chlorides like ethanoyl chloride are colourless fuming liquids.  Acyl chlorides can't be said to dissolve in water because they react (often violently) with it. Their boiling points are high as compared to the alkanes of the same size but lower as compared to corresponding alcohols. Acid chlorides does not form hydrogen bonding.

CHEMICAL PROPERTIES (Reactions) Reaction with water: Adding an acyl chloride to water produces the corresponding carboxylic acid together with steamy acidic fumes of hydrogen chloride. Reaction with phenol: An acid chloride like ethanoyl chloride reacts with phenol to give phenyl ethanoate and hydrogen chloride.

USES Acid chlorides are widely used in the plastics and polymers industries. They are also used in the production of pesticides.