## Abstract

The kinetics and mechanism for the reaction of singlet state CH _{2} with N _{2} have been investigated by ab initio calculations with rate constant prediction. The potential energy surface of the reactions has been calculated by single-point calculations at the CCSD(T)/6-311+G(3df, 2p) level based on geometries optimized at the B3LYP/6-311+G(3df, 2p) level. By comparing the differences in the predicted heats of reaction with the available experimental values, we estimate the uncertainties in the calculated heats of reactions are ±1.4 kcal/mol. Rate constants for various product channels in the temperature range of 300-3000 K are predicted by the variational transition state and RRKM theories. The predicted total rate constants for ^{1}CH _{2} + N _{2} at 760 Torr Ar pressure can be represented by the expressions s-k2 = 9.67 x 10 ^{+7} x T ^{-6.88} exp (-1345/7) cm ^{3} molecule ^{-1} s ^{-1}: at T = 300-2400 K and 3.15 x 10 ^{-229} x T ^{-56.18} exp (128 000/7) cm ^{3} molecule ^{-1} s ^{-1} at T = 2400-3000 K. The branching ratios of the primary channels for ^{1}CH _{2} + N _{2} are predicted: k _{1} for forming singlet s-CH _{2}N _{2}-a (diazomethane) accounts for 0.97-0.01, k _{2} + k _{4} for producing HCNN-a + H accounts for 0.00-0.69, k _{3} for forming singlet s-CH _{2}N _{2}-b (3H-diazirine) accounts for 0.03-0.00, k _{5} for producing HCN + NH accounts for 0.00-0.1.8, and k _{6} for producing CNNH + H accounts for 0.00-0.11l in the temperature range of 300-3000 K. The rate constant predicted for the unimoclecular decomposition of diazomethane producing ^{1}CH _{2} + N _{2} agrees closely with experimental results. Because of the low stability of the two isomeric CH _{2}N _{2} adducts and the high barriers for production of CN-containing products, the contribution of the CH _{2} + N _{2} reaction to NO formation becomes very small.

Original language | English |
---|---|

Pages (from-to) | 5195-5204 |

Number of pages | 10 |

Journal | Journal of Physical Chemistry A |

Volume | 114 |

Issue number | 15 |

DOIs | |

State | Published - 22 Apr 2010 |