The transition state for the epoxidation of ethylene with peroxyformic acid. An ab initio molecular orbital study

Abstract

Acid 743 our calculation (~10 kcal/mol) and the experimental value (~20 kcal/mol) of Zittel et al. In any case, the results of the calculations presented here cannot be reconciled with a singlet-triplet separation in methylene of 19.5 ± 0.7 kcal/mol deduced by Zittel et al. from their experiments. VI. ConclusionThe use of the two-configuration singlet reference state is shown to produce results in agreement with those of the oneconfiguration singlet, if the estimated quadruple excitations corrections are taken into account. A trend is observed which indicates that the 3P carbon atom, the 2 CH radical, and 1Ai methylene are all related, while 5S carbon, 4 ~CH, and 3Bj CH2 are also related. Accurate calculations for C and CH show C(3P) and CH(2n) too high by ~2 kcal/mol relative to C(5S) and € (4 ~), respectively. This indicates that the computed large-basis 1A1 state of methylene is still too high relative to 3B|. Therefore, the correct separation is most likely somewhat smaller than our lowest computed value of 10.6 kcal/mol, and may possibly be as low as 9 kcal/mol.

A Theoretical Study of the Epoxidation of Olefins by Peracids

“…Next, TS1 (Figure ) is in the rate-determining step with an activation energy of 13.5 (13.3) kcal/mol. This energy is somewhat smaller than the reported theoretical ones, 15.8, 15.7, and 16.5 8 kcal/mol. The energy of intermediate B (Figure ) is calculated to be 2.1 (1.3) kcal/mol less than that of the reactants.…”

“…There are only two studies which have used ab initio calculations to study the present reaction. , The first theoretical work reported and compared five approximate transition-state models using minimal basis sets (STO-2G and STO-4G) . In the second work, the transition-state structure was determined with more reliable computational methods (e.g., MP2/6-31G*) …”

Experimental Investigation of the Primary and Secondary Deuterium Kinetic Isotope Effects for Epoxidation of Alkenes and Ethylene with m-Chloroperoxybenzoic Acid

“…Because of its simplicity, ethylene has been used for many of the calculations involving secondary DKIEs accompanying various olefin reactions. ,,− However, to our knowledge, no experimental evidence exists for the secondary DKIE accompanying epoxidation of this simplest olefin. Two other features of the epoxidation mechanism are also of interest, but little experimental information exists.…”

Computational Studies Suggest Promiscuous Candida antarctica Lipase B as an Environmentally Friendly Alternative for the Production of Epoxides

“…First described at the beginning of the 20th century, epoxidation of alkenes using peroxy acids proceeds through a single concerted step where it is believed that the peroxide is positioned perpendicular to the plane of the alkene in the transition state (TS). This mechanism is also known as the butterfly mechanism as coined in the middle of the 20th century by Bartlett, later confirmed by Azman and co-workers, and by Houk and co-workers based on computational studies and kinetic isotope effect (KIE) determinations.…”