THE REACTION OF OZONE WITH MPAN, CH2=C(CH3)C(O)OONO2

The reaction of ozone with the unsaturated peroxyacyl nitrate MPAN, CH 2=C(CH3)C(O)OONO2, has been studied at ppb levels of MPAN and ozone in the dark and with sufficient cyclohexane added to scavenge the hydrox yl radical. The ozone-MPAN reaction rate constant at ambient temperatu re (291-297 K) and atmospheric pressure is (8.2 +/- 2.0) X 10(-18) cm3 molecule-1 s-1 and is consistent with those for other 1,1-disubstitut ed olefins including unsaturated esters that are close structural homo logues of MPAN. The ozone-MPAN reaction mechanism is outlined. Formald ehyde (yield 0.6 +/- 0.1) is the major carbonyl reaction product. Reac tion with ozone may be an important removal process for MPAN in the at mosphere, with, for example, a MPAN half-life of about 18 h when O3 = 50 ppb.