Formation of a 1-Bicyclo[1.1.1]pentyl Anion and an Experimental Determination of the Acidity and C−H Bond Dissociation Energy of 3-<i>tert</i>-Butylbicyclo[1.1.1]pentane
作者:Dana R. Reed、Steven R. Kass、Kathleen R. Mondanaro、William P. Dailey
DOI:10.1021/ja0121890
日期:2002.3.1
by G2 and G3 calculations and can be combined in a thermodynamic cycle to provide a bridgehead C-H bond dissociation energy (BDE) of 109.7 +/- 3.3 kcal/mol for 1-tert-butylbicyclo[1.1.1]pentane. This bond energy is the strongest tertiary C-H bond to be measured, is much larger than the corresponding bond in isobutane (96.5 +/- 0.4 kcal/mol), and is more typical of an alkene or aromatic compound. The
1-双环[1.1.1]戊烷羧酸根阴离子的脱羧不提供先前假设的1-双环[1.1.1]戊基阴离子。相反,会发生最终导致 1,4-戊二烯-2-基阴离子的开环异构化。尽管如此,1-双环[1.1.1]戊基阴离子是通过氟化物诱导的1-叔丁基-3-(三甲基甲硅烷基)双环[1.1.1]戊烷的脱甲硅烷基化制备的。3-叔丁基-1-双环[1.1.1]戊基(14.8+-3.2kcal/mol)的电子亲合力用括号法测定,1-叔丁基-双环[1.1.1]戊烷的酸度( 408.5 +/- 0.9) 由 DePuy 动力学方法确定。这些值通过 G2 和 G3 计算得到了很好的再现,并且可以结合在一个热力学循环中,为 1-叔丁基双环 [1.1.1] 提供 109.7 +/- 3.3 kcal/mol 的桥头 CH 键解离能 (BDE)戊烷。该键能是要测量的最强的叔 CH 键,远大于异丁烷中的相应键 (96.5 +/- 0.4