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首页> 外文期刊>Zeitschrift fur Naturforschung. A, A journal of physical sciences >The Charge Distribution in Amides and Thioamides by Nuclear Quadrupole Coupling, Dipole Moments and Electronic Structure Calculations
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The Charge Distribution in Amides and Thioamides by Nuclear Quadrupole Coupling, Dipole Moments and Electronic Structure Calculations

机译：通过核四极偶合，偶极矩和电子结构计算得出酰胺和硫酰胺中的电荷分布

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摘要

The nuclear quadrupole coupling constants from microwave spectroscopy (MW) and quadrupole resonance (NQR) for amides and thioamides are discussed in relation to Hartree-Fock calculations with and without Moller-Plesset correlation effects. The view that the larger dipole moments from thioamides than the corresponding amides is a function of enhanced resonance in the former is discussed and (in effect) confirmed by the present procedures. The principal mechamism seems to be the push/pull π/σ effects of the N atom with respect to the CO and CS groups, with S being a better σ-donor than O; however, the effect is still present with formamidine where no electronegativity effects are important, so the overall effect is the 2, 1, 1π-electron contribution to the allylic system from N, C, O(S). The use of localised MO's and NO's is described, and the centroid positions are discussed in relation to the polarity of the bonds. The LMO's largely truncate the contributions to each NQCC to the three attached bonds (or 2 bonds + a lone pair orbital at O or S), as is used in the Townes-Dailey procedures. More distant LMO's generally contribute < 0.05 a. u. to the EFG, simplifying the analysis. The effects of O(or S)-protonation of urea and thiourea is discussed.
机译：结合和不考虑Moller-Plesset相关效应的Hartree-Fock计算，讨论了来自微波光谱法（MW）和酰胺和硫代酰胺的四极共振（NQR）的核四极耦合常数。讨论了（实际上）本程序确认了来自硫酰胺的偶极矩大于相应的酰胺的偶极矩是前者增强共振的函数的观点。主要机理似乎是N原子对CO和CS基团的推/拉π/σ效应，其中S是比O更好的σ供体。但是，甲form仍然存在该效应，其中电负性效应并不重要，因此总体效应是N，C，O（S）对烯丙基体系的2，1，1π电子贡献。描述了局部MO和NO的使用，并针对键的极性讨论了质心位置。改性活生物体在很大程度上削减了每个NQCC对三个相连的债券（或2个债券+一个在O或S处的孤对轨道）的贡献，如Townes-Dailey程序所使用的那样。距离较远的LMO通常贡献<0.05 a。你到EFG，简化了分析过程。讨论了尿素和硫脲的O（或S）质子化的影响。

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