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 cyclohexane has been investigated at ambient T and p = 1 atm of air in the 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 reaction products were cyclohexyl methanal (0.62 +/- 0.03) and formaldehyde (0.47 +/- 0.04) from vinylcyclohexane and cyclohexanone (0.55 +/- 0.10) and formaldehyde (0.60 +/- 0.05) from methylene cyclohexane, where the yields given in parentheses are expressed as carbonyl formed, ppb/reacted ozone, ppb. The sum of the yields of the primary carbonyls is close to the value of 1.0 that is consistent with the simple mechanisms: 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 cyclohexane, 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 Wiley G Sons, Inc.