The Ozonolysis of Ethylene. Microwave Spectrum, Molecular Structure, and Dipole Moment of Ethylene Primary Ozonide (1,2,3-Trioxolane)

Article abstract of DOI:10.1021/ja00232a007

The gas-phase structure of ethylene primary ozonide (<*>CH2CH2OOO<*>) has been determined from millimeter wave spectra of five isotopic species.Partial substitution, r_s, parameters for the lowest energy oxygen envelope conformation (C_s symmetry) are r(CC) = 1.546(3) angstroem, r(CO) = 1.417(10) angstroem, r(OO) = 1.453(10) angstroem, r(CH_endo) = 1.088(5) angstroem, r(CH_exo) = 1.095(5) angstroem, θ(CCO) = 103.9(2) deg, θ(COO) = 102.1(4) deg, θ(OOO) = 100.1(12) deg, and θ(HCH) = 111.6(3) deg.The electric dipole moment of the normal isotopic species is 3.43(4) D.Two vibrational states, 98(6) and 171(18) cm^-1 above the ground state, have been assigned to successive excitations of the pseudorotational mode which corresponds to a ring-twisting vibration of the five-membered ring.The barrier to pseudorotation is estimated to be high (greater than 300 to 400 cm^-1) in agreement with ab inito MO calculations.Ethylene primary ozonide, dioxirane (<*>CH2OO<*>), formaldehyde, and ethylene secondary ozonide (<*>CH2OCH2OO<*>) are observed as products of the ozone-ethylene reaction in the low-temperature microwave cell. A mechanism of the ozonolysis of ethylene is presented which suggests that the reaction occurs primarily in the condensed phase on the surface of the cell.Microwave techniques utilizing cis- and trans-CHD=CHD show that ozone adds stereospecifically to ethylene in the formation of ethylene primary ozonide.