Department of Chemistry, Sharif University of Technology, Tehran, Iran.
J Org Chem. 2012 Feb 17;77(4):1909-14. doi: 10.1021/jo202519w. Epub 2012 Jan 30.
Bridgehead C-H bond dissociation enthalpies of 105.7 ± 2.0, 102.9 ± 1.7, and 102.4 ± 1.9 kcal mol(-1) for bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, and adamantane, respectively, were determined in the gas phase by making use of a thermodynamic cycle (i.e., BDE(R-H) = ΔH°(acid)(H-X) - IE(H(·)) + EA(X(·))). These results are in good accord with high-level G3 theory calculations, and the experimental values along with G3 predictions for bicyclo[1.1.1]pentane, bicyclo[2.1.1]hexane, bicyclo[3.1.1]heptane, and bicyclo[4.2.1]nonane were found to correlate with the flexibility of the ring system. Rare examples of alkyl anions in the gas phase are also provided.
桥联 C-H 键离解焓分别为 105.7 ± 2.0、102.9 ± 1.7 和 102.4 ± 1.9 kcal/mol，用于双环[2.2.1]庚烷、双环[2.2.2]辛烷和金刚烷，分别在气相中利用热力学循环（即 BDE（R-H）= ΔH°（酸）（H-X）-IE（H（·））+EA（X（·）））确定。这些结果与高水平 G3 理论计算吻合较好，实验值与 G3 对双环[1.1.1]戊烷、双环[2.1.1]己烷、双环[3.1.1]庚烷和双环[4.2.1]壬烷的预测结果与环系的柔韧性相关。还提供了气相中烷基阴离子的罕见实例。
