Neutralization of methyl cation via chemical reactions in low-energy ion-surface collisions with fluorocarbon and hydrocarbon self-assembled monolayer films
Neutralization of methyl cation via chemical reactions in low-energy ion-surface collisions with fluorocarbon and hydrocarbon self-assembled monolayer films
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通过与碳氟化合物和碳氢化合物自组装单层膜的低能离子表面碰撞中的化学反应来中和甲基阳离子
DOI：
10.1016/s1044-0305(02)00440-3
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发表时间：
2002
影响因子：
3.2
通讯作者：
T. Randall Lee
中科院分区：
文献类型：
--
作者：
Á. Somogyi;Darrin L. Smith;V. Wysocki;R. Colorado;T. Randall Lee
甲基阳离子在碳氢化合物和碳氟化合物自组装单层（SAM）表面的低能离子-表面碰撞产生广泛的CH 3+中和。这些实验观察报告一起获得的结果与分子离子的苯，苯乙烯，3-氟苯甲腈，1，3，5-三嗪，和氨在相同的表面上的离子表面碰撞。为了比较，在三重四极杆（QQQ）仪器中进行了CD 3+和3-氟苯甲腈分子离子与中性正丁烷试剂气体的低能气相碰撞。MP2 6- 31 G ~*//MP2 6- 31 G ~* 的从头算和热化学计算进一步揭示了甲基阳离子的中和机理。数据表明，甲基阳离子与烃和氟碳自组装膜的中和是通过协同化学反应发生的，即，射弹的中和作用不仅通过表面的直接电子转移发生，而且通过非中性分子的形成发生。计算结果表明，在没有明显活化能的情况下，烃表面生成CH_4（氢负离子加成）和C_2H_6（甲基负离子加成），氟碳表面生成CH_3F（氟负离子加成）。结果还表明，在某些情况下，简单的热化学计算不能用来预测的能量分布，因为相对较大的活化能可以与放热反应，如被发现的形成CH 3CF 3（正式加入三氟甲基阴离子）。
Low-energy ion-surface collisions of methyl cation at hydrocarbon and fluorocarbon self-assembled monolayer (SAM) surfaces produce extensive neutralization of CH3+. These experimental observations are reported together with the results obtained for ion-surface collisions with the molecular ions of benzene, styrene, 3-fluorobenzonitrile, 1,3,5-triazine, and ammonia on the same surfaces. For comparison, low-energy gas-phase collisions of CD3+and 3-fluorobenzonitrile molecular ions with neutraln-butane reagent gas were conducted in a triple quadrupole (QQQ) instrument. Relevant MP2 6-31G*//MP2 6-31G*ab initioand thermochemical calculations provide further insight in the neutralization mechanisms of methyl cation. The data suggest that neutralization of methyl cation with hydrocarbon and fluorocarbon SAMs occurs by concerted chemical reactions, i.e., that neutralization of the projectile occurs not only by a direct electron transfer from the surface but also by formation of aneutralmolecule. The calculations indicate that the following products can be formed byexothermicprocessesandwithout appreciable activation energy: CH4(formal hydride ion addition) and C2H6(formal methyl anion addition) from a hydrocarbon surface and CH3F (formal fluoride addition) from a fluorocarbon surface. The results also demonstrate that, in some cases, simple thermochemical calculations cannot be used to predict the energy profiles because relatively large activation energies can be associated with exothermic reactions, as was found for the formation of CH3CF3(formal addition of trifluoromethyl anion).