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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Rearrangement and Fragmentation Processes on the Potential Energy Surfaces of the (CH_nS)~+ (n = 1-4) Systems
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Rearrangement and Fragmentation Processes on the Potential Energy Surfaces of the (CH_nS)~+ (n = 1-4) Systems

机译：（CH_nS）〜+（n = 1-4）系统势能面上的重排和碎片过程

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Stationary points on the quartet and doublet surfaces of (CH_4S)~+, on the triplet and singlet surfaces of (CH_3S)~+, on the singlet and triplet surfaces of (CHS)~+ have been examined by ab initio molecular orbital theory. Equilibrium and saddle point geometries have been located at second-order perturbation theory (UMP2) level using a 6-311++G(d,p) basis set. Relative energies were obtained by means of extensive quadratic configuration interaction singles and doubles calculations with a 6-311++G(2df,2pd) basis set. On the quartet (CH_4S)~+ surface, an association complex stabilized by 25.2 kcal/mol with respect to CH_4 and S~+(~4S) has been identified. Owing to its large barrier (55.5 kcal/mol) for its dissociation, it is expected to be long-lived as assumed by Zakouril et al. (J. Phys, Chem, 1995, 99, 15890) in their experimental work. On the (CH_4S)~+ doublet surface, the conventional methanethiol radical cation expect a competitive isomerization and dissociation. Cleavage of the C-H bonds in the ylide ion involves higher barriers compared to that in CH_3SH~+. Three stable isomers, viz., CH_3S~+, CH_2SH~+, and CHSH_2~+, have been located on the singlet and triplet surfaces of the (CH_3S)~+ system. While CH_2SH~+ is more stable on the singlet surface, CH_3S~+ is more stable on the triplet surface. The molecular hydrogen elimination requires higher barriers from all these isomers compared to radical dissociation. CH_2S~+ is predicted to be more stable that trans-HCSH~+ with a barrier of 51.9 kcal/mol for the rearrangement to the less stable isomer. A significant barrier to 1,2 hydrogen shift isomerization is predicted on the triplet surface of the HSC~+ while that on the singlet surface is predicted to occur without activation energy. The latter signifies an unstable HSC~+ minimum on the singlet surface.
机译：从头算分子轨道理论研究了（CH_4S）〜+的四重峰和双峰表面，（CH_3S）〜+的三重峰和单峰表面，（CHS）〜+的单峰和三重峰表面上的固定点。平衡点和鞍点几何已使用6-311 ++ G（d，p）基集定位在二阶微扰理论（UMP2）级别。相对能量是通过使用6-311 ++ G（2df，2pd）基础集进行的广泛的二次配置相互作用单次和两次计算获得的。在四重体（CH_4S）〜+表面上，已经确定了相对于CH_4和S〜+（〜4S）以25.2 kcal / mol稳定的缔合络合物。由于其解离的障碍很大（55.5 kcal / mol），因此如Zakouril等人所假定的那样，它有望长期存在。 （J. Phys，Chem，1995，99，15890）进行实验。在（CH_4S）〜+双峰表面上，常规的甲硫醇自由基阳离子具有竞争性异构化和离解性。与CH_3SH〜+相比，在Y离子中C-H键的裂解具有更高的势垒。在（CH_3S）〜+系统的单重态和三重态表面上分别存在三个稳定的异构体，即CH_3S〜+，CH_2SH〜+和CHSH_2〜+。 CH_2SH〜+在单线态更稳定，而CH_3S〜+在三线态更稳定。与自由基离解相比，分子氢的消除要求所有这些异构体具有更高的势垒。预测CH_2S〜+比反式HCSH〜+更稳定，势垒为51.9 kcal / mol，可重排至不稳定的异构体。预测在HSC〜+的三重态表面上存在1,2，氢转移异构化的显着障碍，而在单重态表面上，则在没有活化能的情况下发生显着障碍。后者表示单线态表面的HSC〜+最小值不稳定。

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