Knap Hasse C, Jørgensen Solvejg
Department of Chemistry, University of Copenhagen , Universitetsparken 5, 2100 Copenhagen O, Denmark.
J Phys Chem A. 2017 Feb 23;121(7):1470-1479. doi: 10.1021/acs.jpca.6b12787. Epub 2017 Feb 13.
We have used quantum mechanical chemical calculations (CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ) to investigate the hydrogen shift (H-shift) reactions in acyl peroxy and hydroperoxy acyl peroxy radicals. We have focused on the H-shift reactions from a hydroperoxy group (OOH) (1,X-OOH H-shift with X = 6, 7, 8, or 9) in the hydroperoxy acyl peroxy radicals, this H-shift is a reversible reaction and it scrambles between two peroxides, hydroperoxy acyl peroxy and peroxy peroxoic acid radicals. The forward reaction rate constants of the 1,X-OOH H-shift reactions are estimated to be above 10 s with transition state theory corrected with Eckart quantum tunnelling correction. The ratio between the forward and reverse reaction rate constant of the 1,X-OOH H-shift reactions is around ∼10. Therefore, the equilibrium is pushed toward the production of peroxy peroxoic acid radicals. These very fast 1,X-OOH H-shift reactions are much faster than the reactions with NO and HO under most atmospheric conditions and must be included in the atmospheric models when hydroperoxy acyl peroxy radicals are oxidized. Finally, we have observed that H-shift reactions in a pentane acyl peroxy radical (C5-AOO) is fast (>1 s); this can have a significant influence on the possible formation of large acyl peroxy nitrate molecules.
我们运用量子力学化学计算方法（CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ）来研究酰基过氧自由基和氢过氧酰基过氧自由基中的氢迁移（H-迁移）反应。我们重点关注了氢过氧酰基过氧自由基中氢过氧基（OOH）的H-迁移反应（1,X-OOH H-迁移，其中X = 6、7、8或9），这种H-迁移是一个可逆反应，会在氢过氧酰基过氧自由基和过氧过氧酸自由基这两种过氧化物之间发生混乱。经Eckart量子隧穿校正的过渡态理论估计，1,X-OOH H-迁移反应的正向反应速率常数高于10 s。1,X-OOH H-迁移反应的正向和逆向反应速率常数之比约为10左右。因此，平衡倾向于生成过氧过氧酸自由基。在大多数大气条件下，这些非常快速的1,X-OOH H-迁移反应比与NO和HO的反应快得多，当氢过氧酰基过氧自由基被氧化时，大气模型中必须考虑这些反应。最后，我们观察到戊烷酰基过氧自由基（C5-AOO）中的H-迁移反应很快（>1 s）；这可能会对大的酰基过氧硝酸盐分子的可能形成产生重大影响。
