Why are acyl chlorides so reactive?

Question

Isaac Aronson · Accepted Answer

Because they contain (i) an unsaturated carbon centre, and (ii) a potential leaving group in the chloride ion.

The business end of an acyl halide, #RC(=O)X (X=Cl, Br)#, contains a reactive #sp_2# hybridized carbon, and a potential leaving group in the chloride ion. If I ever wanted to perform an esterification reaction, I would always boil up my starting carboxylic acid with thionyl chloride, to give the acid chloride, which would easily react with added alcohol or amine in the presence of a non-nucleophilic base.

Carter Allen · Answer

undefined Acyl chlorides are highly reactive due to the presence of the highly electronegative chlorine atom attached to the carbonyl carbon. This makes the carbonyl carbon highly electrophilic, facilitating nucleophilic attack by other molecules. Additionally, the chloride leaving group is a good leaving group, promoting the reaction. This combination of factors leads to the high reactivity of acyl chlorides in various chemical reactions.

Isaac Aronson · Answer

undefined Acyl chlorides are highly reactive due to the presence of the chloride ion, which is a strong leaving group. This makes it easier for acyl chlorides to undergo nucleophilic substitution reactions with various nucleophiles. Additionally, the polarity of the C=O bond in the acyl chloride molecule enhances its reactivity, as the carbon atom is electrophilic and susceptible to attack by nucleophiles. The presence of the electronegative chlorine atom further increases the electrophilicity of the carbonyl carbon, making acyl chlorides more reactive compared to other carbonyl compounds such as esters or amides.