Deuterium conformational equilibrium isotope effects in 1,3,5-cycloheptatriene-7-<i>d</i>
作者:Darón I. Freedberg、Max Kopelevich、Frank A. L. Anet
DOI:10.1002/poc.410
日期:2001.9
5-cycloheptatriene-7-d (CHT-7-d) by solution 1H NMR at 500 MHz over a wide range of temperatures, and ab initio calculations up to the MP4 level. Lineshape analysis provided a barrier to ring inversion of approximately 6 kcal mol−1. Equilibrium constants were measured in CBrF3 and CClF2H by: integration when the ring-inversion rate is low; lineshape analysis when the ring-inversion rate is on the order of the
我们报告1,3,5-环庚三烯-7-的构象平衡的重新调查d(CHT -7- d通过溶液)1在500MHz在宽的温度范围内的1 H NMR,和从头计算到MP4等级。线形分析为约6 kcal mol -1的环反转提供了障碍。通过以下方法在CBrF 3和CClF 2 H中测量平衡常数:当环反转速率为化学位移差量级时的线形分析;和CHT-7- d之间的温度依赖性和温度依赖性化学位移差异当环反转速率快时。这三个独立的测量值证实了偏向赤道氘的平衡,其中ΔG °= 52±8 cal mol -1(在-173°C时),ΔH °= 55±8 cal mol -1和ΔS ° = 0.03± 0.05calmol -1 K -1在CBrF 3中。支持从头算起的产率为:ΔH °= 34 cal mol -1,ΔS °= 0.014 cal mol -1 K -1(MP2 / 6-31G *);Δ ħ °= 57 CAL摩尔-1和Δ小号°=