CBS-QB3 investigation of the ground-state potential energy surface for the title reaction shows that the initial addition of the chloromethylperoxy radical, CH2ClO2, and NO leads to the CH2ClOONO intermediate formed without energy barrier. Two conformeric forms of CH2ClOONO exhibit different behavior and follow different production pathways. The calculations suggest that the CH2ClO + NO2 radicals are the major products formed through CH2ClOONO intermediate. We demonstrate that the nitrite-nitrate isomerization is significantly facilitated by the assistance of single NO2 molecule compared to the unimolecular isomerization. (C) 2013 Elsevier B.V. All rights reserved.