The influence of a single water molecule on the reaction of IO + HONO.

Depending on the IO approaches the configuration of HONO, two different H-extraction pathways (IO + cis-HONO and IO + trans-HONO) were located at the CCSD(T)//ωB97X-D level. With the introduction of single water molecule, nine pathways were investigated for the IO + HONO reaction. The computed results manifested that the barriers of Pathway W11, Pathway W12, Pathway W21A, Pathway W21B, Pathway W22B, and Pathway W23 are reduced by 0.39, 3.05, 8.14, 12.63, 13.13, and 10.02 kcal/mol, respectively. The rate coefficients of the reaction of IO + cis-HONO and IO + trans-HONO at 298.15 K in the existence of water are 5.98 × 10−13 and 4.93 × 10−11 cm−3 molecule−1 s−1, which are lower than the corresponding reactions in the absence of water (1.14 × 10−14 and 1.39 × 10−19 cm−3 molecule−1 s−1). To further comprehend the influence of H2O on the IO + HONO reaction, the effective rate coefficients were computed through taking account on the water concentration. The effective rate coefficients of the IO + trans-HONO reaction are much larger than the IO + trans-HONO reaction in the absence of water, 'as water molecule could cause the inhibition of the IO + cis-HONO reaction. In contrast to the IO + HONO reaction with water-free, the feasible reaction is the IO + trans-HONO instead of the IO + cis-HONO reaction. The current investigation proved that water possesses positive influence on the IO + trans-HONO reaction, which could devote to the degradation of HONO. [ABSTRACT FROM AUTHOR]