The reaction between ozone and thiophene was studied from 30 to 125°C over a pressure range of 0.005-0.3 torr ozone and 0.1-1 torr thiophene. The most abundant product was 0 2 with smaller amounts of CO, and SOZ. The mass balance was 100% for oxygen and approached 100yo for sulfur a t the higher values of [O&. The carbon balance, however, was only 25% and no H-containing products were found, suggesting that the missing product is a hydrocarbon which may be a polymer. The rate law found waswhere 1,og kl(M-l.sec-l) = 7.8 f 0.5 -(8400 =t 700)/2.3RT, and log k,(M-z-sec-l) = 12.4 f 0.4 -(4700 f 400)/2.3RT. Added O2 had no effect on kl but reduced kz to a limiting value.It is thus not possible to measure the primary rate constant in this system by measuring the overall rate in the presence of oxygen, and this restriction may also apply to other ozone systems. A mechanism is postulated involving two chain sequences, one of which is inhibited by added lo2. A comparison with other ozone systems is made, and the chain lengths are far greater for ozone + thiophene than other systems, under the conditions employed. Possible intermediates in the mechanism are discussed.

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