Unimolecular Thermal Reaction of Formaldoxime at High Temperatures: Experiments and Calculations

Article abstract of DOI:10.1021/j100326a025

The thermal decomposition of formaldoxime diluted in Ar has been studied behind reflected shock waves over the temperature range between 1050 K and 1300 K and the total density range of (0.6-2.4)*10^-5 mol cm^-3.The decomposition process was monitored using the vacuum-UV absorption of the reactant and the IR emission from HCN.It was found that the main thermal reaction proceeded via (1) H2CNOH->H2O+HCN and the alternate isomerization (2) H2CNOH->CH3NO was negligible.Over the temperature range of the study, the decomposition rate constant is k1=10^12.65exp(-48 kcal mol^-1/RT) s^-1.There is a very slight pressure dependence over the experimental region.Ab initio MO calculations were performed for the decomposition and the isomerization channels.The barrier height for the isomerization was higher than that for the molecular decomposition by 24 kcal mol^-1 at the MP2/3-21G level.Rate constants calculated for the dehydration step were in good agreement with those measured.