Abstract
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.
Highlights
Nucleophilicity is a fundamental concept in organic chemistry.[1,2] This property is related to the ability of chemical species, having atoms with lone electron pairs, to react with electron-deficient atoms of other molecules
In a previous paper,[14] we reported an experimental investigation of the reaction of hydroxylamine with five different phenyl acetates
In order to evaluate the importance of catalysis, the pathway for the direct attack of hydroxylamine to phenylacetate was included
Summary
Nucleophilicity is a fundamental concept in organic chemistry.[1,2] This property is related to the ability of chemical species, having atoms with lone electron pairs, to react with electron-deficient atoms of other molecules. Because basicity is related to reactivity, it is expected that the pKa of a protonated nucleophile is correlated to its nucleophilicity through the Brønsted equation: log (k) = bpKa + C (1). This simple correlation may not work in many cases. An interesting example where the breakdown of these. Another important feature of a chemical reaction is the mechanism. Different nucleophiles can react through different mechanisms, leading to the breakdown of
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