Bach Robert D, Dmitrenko Olga
Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
J Am Chem Soc. 2006 Apr 12;128(14):4598-611. doi: 10.1021/ja055086g.
High level ab initio calculations have been applied to the estimation of ring strain energies (SE) of a series of three- and six-member ring compounds. The SE of cyclohexane has been estimated to be 2.2 kcal/mol at the CBS-APNO level of theory. The SE of cyclopropane has been increased to 28.6 kcal/mol after correction for the one-half of the SE of cyclohexane. The SEs of a series of carbonyl-containing three-member ring compounds have been estimated at the CBS-Q level by their combination with cyclopropane to produce a six-member ring reference compound. The SEs of cyclopropanone (5), the simplest alpha-lactone (6) [oxiranone], and alpha-lactam (7) [aziridinone] have been predicted to be 49, 47, and 55 kcal/mol, respectively, after correction for the SE of the corresponding six-member ring reference compound. The SEs of cyclohexanone, delta-valerolactone, and delta-valerolactam have been estimated to be 4.3, 11.3, and 5.1 kcal/mol, respectively. Marked increases in the SE of silacyclopropane and siladioxirane have been established, while significant decreases in the SEs of phosphorus, sulfur, dioxa- and diaza-containing three-member ring compounds were observed. The ring strain energies of the hydrocarbons (but not heterocycles) exhibit a strong correlation with their C-H bond dissociation energies.
高水平的从头算计算已被用于估算一系列三元和六元环化合物的环应变能（SE）。在CBS - APNO理论水平下，环己烷的SE估计为2.2千卡/摩尔。在对环己烷SE的一半进行校正后，环丙烷的SE增加到28.6千卡/摩尔。通过将一系列含羰基的三元环化合物与环丙烷结合生成六元环参考化合物，在CBS - Q水平下估算了它们的SE。在对相应六元环参考化合物的SE进行校正后，环丙酮（5）、最简单的α - 内酯（6）[环氧乙烷酮]和α - 内酰胺（7）[氮杂环丙烷酮]的SE分别预测为49、47和55千卡/摩尔。环己酮、δ - 戊内酯和δ - 戊内酰胺的SE分别估计为4.3、11.3和5.1千卡/摩尔。已确定硅杂环丙烷和硅杂二氧化物的SE有显著增加，同时观察到含磷、硫、二氧和二氮的三元环化合物的SE有显著降低。烃类（而非杂环化合物）的环应变能与其C - H键离解能表现出强烈的相关性。
