IDENTIFICATION OF AN UNEXPECTED PEROXIDE FORMED BY SUCCESSIVE ISOMERIZATION-REACTIONS OF THE N-BUTOXY RADICAL IN OXYGEN

A previously unreported peroxide, C4H8O3 (5), has been identified and its mechanism of formation proposed. It is generated by two successive isomerization reactions of n-C4H9O radicals in O-2. These radicals ar e produced by di-n-C4H9O-OC4H9 pyrolysis at 480 K in a wall-passivated quartz vessel. The peroxide is collected, among other end-products, o n a liquid-nitrogen trap and recovered in liquid acetonitrile. Analysi s was carried out by GC-MS, GC-MS-MS [electron impact (EI) and NH3 (or ND3)-chemical ionization (CI) conditions] and GC-FTIR. After micropre parative GC separation of the titled peroxide, H-1 NMR and high-resolu tion EIMS were also obtained. The compound was identified as 3 alpha-h ydroxy-1,2-dioxane. The hydroperoxybutyraldehyde OHC-(CH2)(2)-CH2O2H i s proposed to be initially formed in the gas phase and to be in equili brium with its cyclic form (six-membered ring peroxide), by far predom inant in the liquid phase at room temperature. The implications of thi s hydroperoxybutyraldehyde in atmospheric pollution (due to the peroxi de producing capability of radicals) and in combustion are discussed.