FORMATION AND CHEMILUMINESCENT DECOMPOSITION OF DIOXETANES IN THE GAS PHASE

Abstract

Abstract— High resolution chemiluminescence spectra have been obtained of the singlet electronically excited products of O2(1Δ) plus alkene, dioxetane forming, reactions. The experiments were conducted in a flow apparatus at pressures of 1–5 torr. The spectra are a measure of the unrelaxed initial distribution of energy in the excited product. Results are reported for ethylene, 1, 1‐difluoroethylene. methyl vinyl ether, ethyl vinyl ether, n‐butyl vinyl ether, ketene, ketene‐d2, allene, unsymdimethyl allene, dimethyl ketene, 2‐methoxy propene, 1‐ethoxy propene, 2‐bromo propene, and N, N‐dimethyl isobutenyl amine. Chemiluminescence activation energies, representing the cycloaddition process, and absolute quantum yields for singlet excited product, ranging from 10‐‐4 to 2.5 × 10‐‐2. are reported for 10 alkenes. Several of the reactions, 1,1‐difluoroethylene, ketene, ethylene and allene give formaldehyde 1nπ* product with excess vibrational‐rotational energy and a higher quantum yield than reactions not displaying this phenomenon. This is an indication of at least partially statistical partitioning of the energy in excess of that needed to electronically excite the formaldehyde. The experiments with ketene and ketene‐d2 provide the first evidence for the existence of unsubstituted 1,2‐dioxetanone. The results from several of the experiments, particularly those with 2‐methoxy propene and I‐ethoxy propene are consistent with the mechanism of Goddard, which predicts regioselective and stereoselective attack of O2(1Δ) upon alkoxy substituted alkenes having allylic hydrogen.