DFT COMPUTATIONAL STUDY OF THE EPOXIDATION OF OLEFINS WITH DIOXIRANES

transition structures (TSs) of the reactions of dioxirane and dimethyl dioxirane with ethylene, propene, cis-2-butene and trans-2-butene were located with the B3LYP/6-31G method. The TSs of the reactions of eth ylene and cis-2-butene exhibit a symmetrical spiro butterfly structure with synchronous formation of the two new C-O bonds and with substant ial alignment of rr bond axis with the breaking O-O bond. In the case of propene and trans-2-butene a slight asynchrony in C--O bond formati on was predicted by calculations. Theoretical activation free enthalpi es (gas phase) reproduce the experimental (acetone solution) higher re activity of cis with respect to trans disubstituted alkenes which in t urn are correctly predicted more reactive than monosubstituted alkenes . Also the calculated absolute activation free enthalpies, after corre ction for electrostatic solvation effects by single point SCRF calcula tion (Tomasi model), were found to be in reasonable accord with experi mental data. (C) 1998 Elsevier Science Ltd. All rights reserved.