The reaction of hydroxylamine with phenyl acetate was theoretically investigated to shed light on the role of catalysis and the origin of the α-effect in this system. Calculations at the B3LYP/6-311+G(2df,2p)//HF/6-31G(d) level and the solvent effect included at the PCM/HF/6-31G(d) level predict that the direct attack of hydroxylamine to the carbonyl centre has a high ΔG‡ barrier, close to 50 kcal mol-1. A second hydroxylamine molecule can catalyse the process through bifunctional catalysis using both the NH2 and OH groups simultaneously. This dual bifunctional catalysis decreases the ΔG‡ to 19 kcal mol-1 and is able to explain the experimentally observed kinetics and product ratio.
acid-base catalysis; organocatalysis; alpha-effect; zwitterionic intermediate; solvent effect
