Atsüülhalogeenid

Atsüülhalogeenid, also known as acyl halides, are a class of organic compounds characterized by the functional group R-CO-X, where R is an alkyl or aryl group, and X is a halogen atom (typically chlorine, bromine, or iodine). They are derivatives of carboxylic acids, formed by replacing the hydroxyl (-OH) group of the carboxylic acid with a halogen atom. This substitution significantly increases the reactivity of the carbonyl carbon due to the electronegativity of the halogen atom, which withdraws electron density from the carbonyl group.

The general formula for an acyl halide is RCOX. Common examples include acetyl chloride (CH3COCl), benzoyl chloride (C6H5COCl), and propionyl bromide (CH3CH2COBr). They are typically prepared by reacting the corresponding carboxylic acid with a halogenating agent such as thionyl chloride (SOCl2), phosphorus trichloride (PCl3), or phosphorus pentachloride (PCl5).

Atsüülhalogeenid are highly reactive and readily undergo nucleophilic acyl substitution reactions. They react vigorously with water to regenerate the parent carboxylic acid and hydrogen halide. They also react with alcohols to form esters, with amines to form amides, and with Grignard reagents to form tertiary alcohols. Due to their reactivity, they are often used as intermediates in organic synthesis for the preparation of other carboxylic acid derivatives. Their high reactivity also makes them corrosive and they often produce irritating fumes.