Kinetics of the Difluoromethylene—Nitric Oxide Reaction. I

Abstract

Evidence from mass spectra and ultraviolet‐light absorption behind shock waves indicates a reversible reaction $${\mathrm{CF}}_2+\mathrm{NO}\rightleftharpoons {\displaystyle {lim}_{k_{1^{\prime }}}^{k_1}}{\mathrm{CF}}_2\mathrm{NO}$$ between difluoromethylene and nitric oxide. Above 2500°K the reaction proceeds further to equilibrium by $$2{\mathrm{CF}}_2\mathrm{NO}\text{→2}{\mathrm{CF}}_2\mathrm{O}+{\mathrm{N}}_2$$ and $${\mathrm{CF}}_2\mathrm{NO}+\mathrm{NO}\to {\mathrm{CF}}_2\mathrm{O}+{\mathrm{N}}_2\mathrm{O}.$$ In the temperature interval 1600°—2500°K, oscillogram records of CF₂ uv absorption are reduced in terms of [1,1′] by the rate law $\mathrm{-d[}{\mathrm{CF}}_2{\mathrm{]/dt=k}}_1[{\mathrm{CF}}_2\mathrm{][}\mathrm{NO}{\mathrm{]-k}}_{1^{\prime }}[{\mathrm{CF}}_2\mathrm{NO}]$ with $$k_1{\text{=10}}^{\text{13.951±0.338}}\hspace{0.17em}\exp \text{(−29200±3300/RT)\hspace{0.17em}}\mathrm{cc}/\mathrm{mole}·\sec$$ and $$k_{1^{\prime }}{\text{=10}}^{\text{6.497±0.393}}\hspace{0.17em}\exp \text{(−20600±3600/RT)\hspace{0.17em}}{\sec }^{\text{−1}}.$$ From the ratio k₁/k_1′, the heat of reaction [1] is found to be 4.6 kcal/mole, yielding a heat of formation of the CF₂NO radical equal to −15.7 kcal/mole.