Aromatic C-nitroso compounds. Thermodynamics and kinetics of the equilibrium between 2,6-dimethylnitrosobenzene and its trans-dimer

Abstract

Using i.r., n.m.r. and visible spectrophotometry, the system 2,6-dimethylnitrosobenzene (DMNB)⇄ 2,2′,6,6′-tetramethylazodioxybenzene (TMAB) was investigated. In the solid state, the stable species is trans-TMAB. In acetonitrile solution, the following thermodynamic and activation parameters were derived for the reaction trans-TMAB ⇄ 2 DMNB ΔH°–54.0 kJ mol^–1, ΔS°–129 J K^–1 mol^–1, ΔH^‡ 84.5 kJ mol^–1, and ΔS^‡–6 J K^–1 mol^–1. There was no evidence for the existence of cis-TMAB in solution.