首页> 外文期刊>Journal of the Chemical Society. Perkin Transactions 2 >Small steric effects in isolated molecules: alkyl-substituted benzonitriles
【24h】

Small steric effects in isolated molecules: alkyl-substituted benzonitriles

机译:分离的分子中的小空间效应:烷基取代的苄腈

获取原文
获取原文并翻译 | 示例
获取外文期刊封面目录资料

摘要

A series of seven alkyl-substituted benzonitriles was investigated as a model for small steric effects (van der Waals tension) excluding any steric inhibition due to resonance. The energies were calculated at it B3LYP/6-311 +G(d,p) level and the gas-phase basicities of some compounds were measured by Fourier-transform ion cyclotron resonance. Substituent effects were evaluated separately for neutral molecules and protonated forms by means of isodesmic reactions, and dissected into polar and steric effects by comparing ortho and para derivatives. One or two ortho methyl groups have a relatively small steric effect operating almost exclusively in the protonated form which leads to weakened basicity. An ortho tert-butyl group exerts a strong steric effect both in the protonated and nonprotonated forms, manifested also in a rather strong distortion of geometry. The effect on basicity is then a small difference of two large values and is base strengthening. Acid-base properties are in such cases a poor measure of substituent effects and cannot be interpreted in simple terms. [References: 41]
机译:研究了一系列七个烷基取代的苄腈作为模型,以排除由于共振引起的任何空间抑制作用,从而获得较小的空间效应(范德华张力)。计算能量为B3LYP / 6-311 + G(d,p),并通过傅立叶变换离子回旋共振测量某些化合物的气相碱度。通过等离子反应分别评估中性分子和质子化形式的取代作用,并通过比较邻位和对位衍生物将其分解为极性和空间作用。一个或两个邻甲基具有相对​​较小的空间效应,几乎仅以质子化形式起作用,这导致弱碱性。邻叔丁基以质子化形式和非质子化形式均表现出强烈的空间效应,还表现出相当强的几何形变。这样,对碱性的影响就是两个较大值之间的很小差异,并且是基础增强。在这种情况下,酸碱性质不能很好地衡量取代基的效果,因此不能用简单的术语来解释。 [参考:41]

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