trimethylbenzyl cation | 20615-38-7

• 分子结构分类: 有机化合物 - 苯类化合物 - 苯和取代衍生物
• 英文名称: trimethylbenzyl cation
• 英文别名: 1-methyl-2-propan-2-ylbenzene
• CAS: 20615-38-7
• 化学式: C₁₀H₁₃
• 分子量: 133.213
• InChiKey: OWXUCUQVKBCZKB-UHFFFAOYSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  3.4
• 重原子数：
  10
• 可旋转键数：
  1
• 环数：
  1.0
• sp3杂化的碳原子比例：
  0.3
• 拓扑面积：
  0
• 氢给体数：
  0
• 氢受体数：
  0

反应信息

• 作为产物：
  描述：

  2-异丙烯基甲苯 在 硫酸 、 水 作用下， 以 甲醇 为溶剂， 生成 trimethylbenzyl cation
  参考文献：
  名称：

  ortho-Effect on the acid-catalyzed hydration of 2-substituted α-methylstyrenes

  摘要：

  α-甲基苯乙烯和九个邻位取代物已经合成，并研究了它们在25°C硫酸水溶液中酸催化水合的动力学。动力学酸度函数HS已经根据观察到的速率常数kobs对硫酸浓度的依赖关系构建。酸催化水合的催化速率常数kortho也已计算。邻位取代物和对位取代物的动力学酸度函数的相同形状证实了酸催化水合的一致机制A-SE2已经为相应的对位取代物证明。A-SE2机制涉及水合质子向底物的速率决定性质子转移。从邻位取代物的催化速率常数依赖于对位取代物的催化速率常数的关系中可以看出，氢作为取代基的催化速率常数的对数明显超出了其他取代基的范围，并且同时，邻位取代物的反应速度明显比相应的对位取代物慢。与取代基常数σp+的相关性，发现了一个反应常数ρ+ = -1.45。该常数的绝对值比对位取代物的常数（ρ+ = -3.07）要小得多。与取代基常数的斜率3.92相比，对于包含更多原子的取代基（Charton常数的斜率为2.09），单原子取代基的立体效应更为显著。由于反应中心与苯环之间的共轭减弱，导致反应中心扭曲出主要芳香平面并伴随着与连接到苯环的取代基之间的消退的共轭作用，解释了反应常数ρ+的小值。对于单原子取代基，卡宾离子中的异丙基团扭曲得较少，因此，取代基的体积差异对卡宾离子与携带取代基的苯环之间的共轭影响很大。相反，对于具有多原子取代基的卡宾离子中的异丙基团扭曲程度较大，因此，取代基体积的变化对共振稳定化的影响微乎其微。类似的结论也可以从取代常数σI和σR+的相关性推导出。

  DOI：

  10.1135/cccc2008115

文献信息

• ortho-Effect on the acid-catalyzed hydration of 2-substituted α-methylstyrenes
  作者：Ondřej Prusek、Filip Bureš、Oldřich Pytela

  DOI：10.1135/cccc2008115

  日期：——

  α-Methylstyrene and nine ortho-substituted analogs have been synthesized and the kinetics of their acid-catalyzed hydration in aqueous solutions of sulfuric acid at 25 °C have been investigated. The kinetic acidity function H_S has been constructed from the dependence of the observed rate constants k_obs on the sulfuric acid concentration. The catalytic rate constants of the acid-catalyzed hydration k_ortho have been calculated as well. The identical shape of the kinetic acidity functions for ortho- and para-derivatives confirms what the consistent mechanism A-SE2 of the acid-catalyzed hydration has already proved for the corresponding para-derivatives. The A-SE2 mechanism involves a rate-determining proton transfer of the hydrated proton to the substrate. From the dependence of the catalytic rate constants of the ortho-derivatives on the catalytic rate constants of the para-derivatives, it is seen that the logarithm of the catalytic rate constant for hydrogen as a substituent is markedly out of the range of the other substituents and, simultaneously, that the ortho-derivatives react significantly slower than the corresponding para-derivatives. In correlation with the substitent constants σ_p⁺, a reaction constant of ρ⁺ = –1.45 have been found. The constant is, in absolute value, considerably smaller than that for para-derivatives (ρ⁺ = –3.07). In parallel, the steric effects are enforced more significantly for the monoatomic substituents (slope of the Charton’s constants 3.92) than for substituents including more atoms (slope of the Charton’s constants 2.09). A small value of the reaction constant ρ⁺ has been elucidated due to the lower conjugation between the reaction centre and the benzene ring as a consequence of the geometric twist of the reaction centre out of the main aromatic plane accompanied by fading mesomeric interaction between the reaction centre and the substituents attached to the benzene ring. The isopropyl group in the carbocation is twisted less out of the aromatic plane for the monoatomic substituents and, therefore, also a small difference in the bulk of substituents has considerable steric influence on the conjugation between the carbocation and the benzene ring bearing substituents. On the contrary, the isopropyl group in the carbocations with polyatomic substituents is twisted to such a degree that changes in the bulk of substituents affect the resonant stabilization negligibly. Similar conclusions were also deduced from the correlations of the substitution constants σI and σ_R⁺.

  α-甲基苯乙烯和九个邻位取代物已经合成，并研究了它们在25°C硫酸水溶液中酸催化水合的动力学。动力学酸度函数HS已经根据观察到的速率常数kobs对硫酸浓度的依赖关系构建。酸催化水合的催化速率常数kortho也已计算。邻位取代物和对位取代物的动力学酸度函数的相同形状证实了酸催化水合的一致机制A-SE2已经为相应的对位取代物证明。A-SE2机制涉及水合质子向底物的速率决定性质子转移。从邻位取代物的催化速率常数依赖于对位取代物的催化速率常数的关系中可以看出，氢作为取代基的催化速率常数的对数明显超出了其他取代基的范围，并且同时，邻位取代物的反应速度明显比相应的对位取代物慢。与取代基常数σp+的相关性，发现了一个反应常数ρ+ = -1.45。该常数的绝对值比对位取代物的常数（ρ+ = -3.07）要小得多。与取代基常数的斜率3.92相比，对于包含更多原子的取代基（Charton常数的斜率为2.09），单原子取代基的立体效应更为显著。由于反应中心与苯环之间的共轭减弱，导致反应中心扭曲出主要芳香平面并伴随着与连接到苯环的取代基之间的消退的共轭作用，解释了反应常数ρ+的小值。对于单原子取代基，卡宾离子中的异丙基团扭曲得较少，因此，取代基的体积差异对卡宾离子与携带取代基的苯环之间的共轭影响很大。相反，对于具有多原子取代基的卡宾离子中的异丙基团扭曲程度较大，因此，取代基体积的变化对共振稳定化的影响微乎其微。类似的结论也可以从取代常数σI和σR+的相关性推导出。