Quantum chemical calculation of structures and NMR chemical shifts of substituted buta‐1,3‐dienyl‐2‐cations
Quantum chemical calculation of structures and NMR chemical shifts of substituted buta‐1,3‐dienyl‐2‐cations
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取代丁-1,3-二烯基-2-阳离子的结构和NMR化学位移的量子化学计算
DOI：
10.1002/poc.838
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Sandra Brixner
中科院分区：
文献类型：
--
作者：
H. Siehl;Sandra Brixner
本文计算了一系列α-乙烯基取代的乙烯基阳离子（1，3-二烯基-2-阳离子）1-6的~（1,3）C NMR化学位移。预测的各向同性位移的电子相关性，基组和几何效应的敏感性进行了探讨。与实验13 C NMR化学位移的比较表明，二级Moller-Plesset微扰理论计算[GIAO-MP2/tzp//MP2/6- 31 G（d，p）]对阳离子1-6的所有碳都有足够的计算结果（偏差为1.3 -4 ppm），除了6中涉及环丙基超共轭的碳，其偏差较大（1.6 -9 ppm）。Hartree-Fock自洽场（GIAO-HF/tzp）近似以及GIAO-DFT方法与杂化泛函（B3 LYP）一起给出了不令人满意的结果，并且不能依赖于预测这些类型的碳正离子的13 C NMR谱中的信号序列。版权所有© 2004年约翰威利父子有限公司。
A computational study of 13C NMR chemical shifts of a series of α-vinyl substituted vinyl cations (1,3-dienyl-2-cations) 1–6 is presented. The sensitivity of the predicted isotropic shifts to electron correlation, basis set and geometry effects is explored. Comparison with experimental 13C NMR chemical shifts shows that second-order Moller–Plesset perturbation theory calculations [GIAO-MP2/tzp//MP2/6–31G(d,p)] perform adequately (deviation ≈ 3–4 ppm) for all carbons of cations 1–6, except for carbons in 6 involved in cyclopropyl hyperconjugation, which give some larger deviations (≈ 6–9 ppm). The Hartree–Fock self-consistent field (GIAO-HF/tzp) approximation as well as GIAO-DFT-methods together with hybrid functionals (B3LYP) give unsatisfactory results and cannot be relied upon to predict the sequence of signals in the 13C NMR spectra of these type of carbocations. Copyright © 2004 John Wiley & Sons, Ltd.