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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Associative charge transfer reactions. temperature effects and mechanism of the gas-phase polymerization of propene initiated by a benzene radical cation
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Associative charge transfer reactions. temperature effects and mechanism of the gas-phase polymerization of propene initiated by a benzene radical cation

机译：缔合电荷转移反应。苯自由基阳离子引发的丙烯气相聚合反应的温度效应及机理

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摘要

In associative charge transfer (ACT) reactions, a core ion activates ligand molecules by partial charge transfer. The activated ligand polymerizes, and the product oligomer takes up the full charge from the core ion. In the present system, benzene(+.) (Bz(+.)) reacts with two propene (Pr) molecules to form a covalently bonded ion, C6H6+. + 2 C3H6 -> C6H12+. + C6H6. The ACT reaction is activated by a partial charge transfer from Bz(+.) to Pr in the complex, and driven to completion by the formation of a covalent bond in the polymerized product. An alternative channel forms a stable association product (Bz, Pr)(+.), with an ACT/association product ratio of 60:40% that is independent of pressure and temperature. In contrast to the Bz(+.)/propene system, ACT polymerization is not observed in the Bz(+.)/ethylene (Et) system since charge transfer in the Bz(+.)(Et) complex is inefficient to activate the reaction. The roles of charge transfer in these complexes are verified by ab initio calculations. The overall reaction of Bz(+.) with Pr follows second-order kinetics with a rate constant of k (304 K) = 2.1 x 10(-12) cm(3) s(-1) and a negative temperature coefficient of k = aT(-5.9) (or an activation energy of -3 kcal/mol). The kinetic behavior is similar to sterically hindered reactions and suggests a [ Bz(+.) (Pr)]* activated complex that proceeds to products through a low-entropy transition state. The temperature dependence shows that ACT reactions can reach a unit collision efficiency below 100 K, suggesting that ACT can initiate polymerization in cold astrochemical environments.
机译：在缔合电荷转移（ACT）反应中，核心离子通过部分电荷转移激活配体分子。活化的配体聚合，产物低聚物从核心离子吸收全部电荷。在本系统中，苯（+。）（Bz（+。））与两个丙烯（Pr）分子反应形成共价键合离子C6H6 +。 + 2 C3H6-> C6H12 +。 + C6H6。 ACT反应通过从配合物中Bz（+）到Pr的部分电荷转移而被激活，并通过在聚合产物中形成共价键而被驱动完成。替代通道形成稳定的缔合产物（Bz，Pr）（+。），其ACT /缔合产物比率为60：40％，与压力和温度无关。与Bz（+。）/丙烯系统相反，在Bz（+。）/乙烯（Et）系统中未观察到ACT聚合，因为Bz（+。）（Et）络合物中的电荷转移无法有效激活Bz（+。）/丙烯系统。反应。电荷转移在这些配合物中的作用通过从头算来验证。 Bz（+。）与Pr的整体反应遵循二级动力学，速率常数为k（304 K）= 2.1 x 10（-12）cm（3）s（-1），负温度系数为k ＝ aT（-5.9）（或-3kcal / mol的活化能）。动力学行为类似于位阻反应，并表明[Bz（+。）（Pr）] *活化的络合物可通过低熵的过渡态转化为产物。温度依赖性表明，ACT反应可以达到低于100 K的单位碰撞效率，这表明ACT可以在寒冷的地球化学环境中引发聚合反应。

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