ENTHALPIES OF FORMATION OF CYCLIC ALKYL PEROXIDES - DIOXANE, 1,2-DIOXETANE, 1,2-DIOXOLANE, AND 1,2-DIOXANE

摘要

Enthalpies of formation of four cyclic alkyl peroxides are calculated using ab initio methods. The values are reported as: Delta H(f298)degrees(dioxirane) = -2.91 +/- 1.34 kcal/mol, Delta H(f298)degrees(1,2-dioxetane) = 1.09 +/- 0.51, Delta H(f298)degrees(1,2-dioxolane) = -27.43 +/- 0.91 kcal/mol, and Delta H(f298)degrees(1,2-dioxane) = -31.74 +/- 0.96 kcal/mol. Enthalpies of formation for 1,2-dioxetane, 1,2-dioxolane, and 1,2-dioxane are calculated using isodesmic reactions at the MP4SDTQ/6-31G**//MP2/6-31G* level of theory. These isodesmic reactions are 'group balanced'. For dioxirane, reaction energies of two reactions are calculated using the G2 method. The difference of Delta H(f298)degrees(dioxirane) values determined using these two reactions is within 0.7 kcal/mol. Ring strain energies (in kcal mol-L) are determined as 30.7, 26.7, 7.3, 4.0 for dioxirane, 1,2-dioxetane, 1,2-dioxolane, and 1,2-dioxane, respectively. Comparisons are also made with a scaled PM3 estimation, and results are in reasonable agreement with the recommended values. [References: 19]