The Kinetics of Nitrosation of Phenyl Cyclohexanecarboxylate with Nitrosyl Hydrogensulfate in Sulfuric Acid

Abstract

The rates of the nitrosation of phenyl cyclohexanecarboxylate (abbreviated as PCC) with nitrosyl hydrogensulfate (NHS) in 0-7% oleum to form ε-caprolactam have been investigated by measuring the volume of evolved carbon dioxide. The rate equation of the reaction is written as follows : Rate=(κ_1e+κ_2esC_so3+κ_2enC_NHS)C_PCC A probable mechanism which involves the rate-determining steps of formation of pentamethylene ketene (PMK) by deprotonation from cyclohexanecarbonyl cation formed by elimination of phenolate anion and sulfur trioxide from an adduct of PCC and SO₃ (κ₁, main path, 90.4%), and by the elimination of SO₃, phenol and proton from the adduct (κ_2es, 5.3%) followed by a rapid attack of NHS on the double bond of PMK, and a rate-determining formation of cyclohexanone oxime hydrogensulfate from the adduct of NHS and PCC (κ_2en, 4.3%) was discussed and postulated.