A KINETIC AND PRODUCT STUDY OF THE GAS-PHASE REACTION OF OZONE WITH VINYLCYCLOHEXANE AND METHYLENE CYCLOHEXANE

The gas-phase reaction of ozone with vinylcyclohexane and methylene cy clohexane has been investigated at ambient T and p = 1 atm of air in t he presence of sufficient cyclohexane or 2-propanol added to scavenge OH. The reaction rate constants, in units of 10(-18) cm(3) molecule(-1 ) s(-1), are 7.52 +/- 0.97 for vinylcyclohexane (T = 292 +/- 2 K) and 10.6 +/- 1.9 for methylene cyclohexane (T = 293 +/- 2 K). Carbonyl rea ction products were cyclohexyl methanal (0.62 +/- 0.03) and formaldehy de (0.47 +/- 0.04) from vinylcyclohexane and cyclohexanone (0.55 +/- 0 .10) and formaldehyde (0.60 +/- 0.05) from methylene cyclohexane, wher e the yields given in parentheses are expressed as carbonyl formed, pp b/reacted ozone, ppb. The sum of the yields of the primary carbonyls i s close to the value of 1.0 that is consistent with the simple mechani sms: O-3 + cyclo(C6H11) - CH = CH2 --> alpha(HCHO + cyclo(C6H11)CHOO) + (1 - alpha) (HCHOO + cyclo(C6H11)CHO) for vinylcyclohexane and O-3 (CH2)(5)C = CH2 --> alpha(HCHO + (CH2)(5)COO) + (1 - alpha)(HCHOO + ( CH2)(5)C = O) for methylene cyclohexane. The coefficients alpha are 0. 43 +/- 0.10 for vinylcyclohexane and 0.52 +/- 0.05 for methylene cyclo hexane, i.e., (formaldehyde + the substituted biradical) and (HCHOO cyclohexyl methanal or cyclehexanone) are formed in ca. equal yields. Reaction rate constants, carbonyl yields, and reaction mechanisms are compared to those for alkene structural homologues. (C) 1997 John Wile y G Sons, Inc.