atsetüülhalogeenhapped

Atsetüülhalogeenhapped, also known as acyl halides or acid halides, are a class of organic compounds derived from carboxylic acids. In these compounds, the hydroxyl group (-OH) of a carboxylic acid is replaced by a halogen atom, typically chlorine or bromine. The general formula for an acyl halide is R-CO-X, where R represents an alkyl or aryl group and X represents a halogen atom (F, Cl, Br, or I). However, the most commonly encountered and synthetically useful acyl halides are the acyl chlorides and acyl bromides.

These compounds are characterized by the highly polarized carbonyl group (C=O) and the electronegative halogen atom, which makes the carbonyl carbon very electrophilic. This electrophilicity is the key to their reactivity. Atsetüülhalogeenhapped are highly reactive acylating agents, meaning they readily donate the acyl group (R-CO-) to nucleophiles. This reactivity makes them valuable intermediates in organic synthesis.

They are typically prepared by reacting carboxylic acids with halogenating agents such as thionyl chloride (SOCl2), phosphorus trichloride (PCl3), or phosphorus pentachloride (PCl5). Atsetüülhalogeenhapped are often lachrymatory, meaning they can cause tears, and they react vigorously with water, hydrolyzing back to the corresponding carboxylic acid and hydrogen halide. Due to their reactivity and moisture sensitivity, they are often prepared and used in situ or stored under anhydrous conditions. Common reactions include esterification, amidation, and Friedel-Crafts acylation.