Theoretical investigation of lone pair inversions, ring openings, and hydride shifts in O-methylated epoxides.
Theoretical investigation of lone pair inversions, ring openings, and hydride shifts in O-methylated epoxides.
复制标题
O-甲基化环氧化物中孤对电子反转、开环和氢化物位移的理论研究。
DOI：
--
复制
发表时间：
2007
影响因子：
3.6
通讯作者：
B. K. Ohta
中科院分区：
文献类型：
--
作者：
Jeffrey W. Schubert;Timothy J. Dudley;B. K. Ohta
用相关电子结构计算探讨了O-甲基乙烯氧鎓离子及其四甲基取代类似物的异构化机理。的极小值和过渡态与反转在氧原子，以及那些与开放的环氧环，其特征在于。计算的O-甲基乙烯氧鎓离子在氧原子处的反转势垒为15.7 kcal/mol，与实验测定值10+/-2 kcal/mol吻合得很好。我们的计算表明，一个显着更高的障碍存在的开环机制，导致更稳定的结构。这项工作包括O-甲基-2，3-二甲基-2-丁烯氧鎓离子沿着过渡态和中间体与开环和反转在氧原子上的第一个已知的计算。结果表明，与O-甲基乙烯氧鎓离子物种相比，开环屏障显着较低，导致分离该物种的可能性较低。本文还分析了基组和相关技术对这些离子的影响。我们的结果表明，B3 LYP/6- 31 G * 水平是可靠的获得分子的几何构型的最低和过渡态的C3 H7 O+和C7 H15 O+势能面。
Mechanisms associated with the isomerization of the O-methylethylene oxonium ion and its tetramethyl-substituted analogue have been explored using correlated electronic structure calculations. The minima and transition states associated with inversion at the oxygen atom, as well as those associated with opening of the epoxide ring, have been characterized. The calculated barrier to inversion at the oxygen atom for the O-methylethylene oxonium ion, 15.7 kcal/mol, agrees well with the experimentally determined value, 10+/-2 kcal/mol. Our calculations indicate that a significantly higher barrier exists for the ring-opening mechanism that leads to more thermodynamically stable structures. This work includes the first known calculations on the O-methyl-2,3-dimethyl-2-butene oxonium ion along with transition states and intermediates associated with ring opening and inversion at the oxygen atom. Results show that there is a significantly lower barrier to ring opening as compared to the O-methylethylene oxonium ion species, leading to a lower probability of isolating this species. The effects of basis sets and correlation techniques on these ions were also analyzed in this work. Our results indicate that the B3LYP/6-31G* level is reliable for obtaining molecular geometries for both minima and transition states on the C3H7O+ and C7H15O+ potential energy surfaces.