Vacuum–ultraviolet photolysis (185 nm) of liquid 1,3-dioxan

1,3-Dioxan photolytic destruction at 185 nm occurs with a quantum yield of about 0.3 in the liquid phase. Of the 22 products determined, the major ones are n-propylformate [Formula: see text], formaldehyde (0.075), 1,3-diox-4-en (0.06), hydrogen (0.05), ethylene (0.04), and 3-methoxypropionaldehyde (0.04). A number of the minor products are of the general type B.[Formula: see text]some of which bear a hydroxyl function at the end of the side chain. N2O interacts with excited 1,3-dioxan, leading to the production of N2.Some experiments have been carried out in the vapour phase, the results of which indicate that considerable fragmentation of hot primary intermediates and products into low-molecular-weight products occurs. The nature of these products cannot be linked directly to the primary photolytic processes inferred from the liquid-phase studies.Certain contrasts in the photolytic behaviour of 1,3-dioxan and 1,4-dioxan are discussed.