...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of structural chemistry >Anomeric effect and theoretical vibrational spectra compared to the experiment in 2-chloro-1,3,2-dioxaphosphorinane-2-oxide, -sulfide, and -selenide. I. Anomeric effect and structures
【24h】

Anomeric effect and theoretical vibrational spectra compared to the experiment in 2-chloro-1,3,2-dioxaphosphorinane-2-oxide, -sulfide, and -selenide. I. Anomeric effect and structures

机译：与2-氯-1,3,2-二氧杂磷氧杂环丁烷-2-氧化物，-硫化物和-硒化物的实验相比，其端粒效应和理论振动光谱有所不同。一，端粒效应和结构

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

2-Chloro-1,3,2-dioxaphosphorinane-2-oxide, -sulfide, and -selenide are studied at the DFT/B3LYP level and several ab initio methods using a 6-311G** basis set. Our energy optimizations by all these methods show that for oxide DFT and ab initio methods are not much different, while for the sulfide and the selenide the DFT relative energies are higher by about a kcal/mol as compared to those of MP2, MP3, MP4(SDTQ)//MP2, and CCSD(T)//MP2 (//MP2 indicates that a single-point calculation based on the MP2 optimized geometry is performed). However, regardless of rather large relative energies, that does not change the fact that in all three cases the conformational equilibrium mixture contains more than 95% of the lowest, chair -equatorial conformer (this indicates that the P=X bond is in equatorial position). This one and the next higher conformer (chair -axial) are confirmed to be real conformers (energy minima) in all cases. The energetically much higher twist and boat forms are probably just stationary states and local maxima because in many cases, geometry optimizations do not converge to them. Only for MP2 and the selenide do all optimizations converge to the desired stationary state. The relative energies could all be explained in terms of anomeric effects and ring strains. The decreasing covalent character of the P=X bond, with X changing from O to S and to Se, shows itself in the increasing bond lengths and the decreasing strength of anomeric effects.
机译：在DFT / B3LYP水平上使用2-311G **基集从头算方法研究了2-氯-1,3,2-二氧杂磷杂环丁烷-2-氧化物，-硫化物和-硒化物。我们通过所有这些方法进行的能量优化表明，氧化物DFT和从头算方法没有太大差异，而对于硫化物和硒化物，DFT的相对能量比MP2，MP3，MP4的相对能量高约kcal / mol。 （SDTQ）// MP2和CCSD（T）// MP2（// MP2表示执行了基于MP2优化几何的单点计算）。但是，无论相对能量较大，这都不会改变以下事实：在所有三种情况下，构象平衡混合物均包含95％以上的最低的赤道赤道构象异构体（这表明P = X键处于赤道位置）。在所有情况下，这个和下一个较高的构象异构体（椅轴）被确认为真实的构象异构体（能量最小值）。能量上高得多的扭曲和船形可能只是静止状态和局部最大值，因为在许多情况下，几何优化不会收敛到它们。仅对于MP2和硒化物，所有优化都会收敛到所需的静止状态。相对能量都可以用异头作用和环应变来解释。 P = X键的共价特性下降，X从O变为S，再变为Se，表现为键长度增加和端基异头作用强度降低。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号