ENE REACTIONS OF OLEFINS .1. ADDITION OF ETHYLENE TO 2-BUTENE AND DECOMPOSITION OF 3-METHYLPENTENE-1

The pyrolysis of ethylene–butene‐2 mixtures has been studied in a static system over the temperature range of 689°‐754°k and for initial pressures of each olefin of 20–200 torr. The two main addition products were cyclopentene and 3‐methylpentene‐1. Kinetic evidence indicated that cyclopentene was formed from radical processes while 3‐methylpentene‐1 was formed by the molecular “ene¨︂” addition of ethylene to butene‐2 through a six‐center transition state. The following rate constants were obtained: (Formula Presented.) The pyrolysis of 3‐methylpentene‐1 has been studied over the same temperature range and for initial pressures of 20–100 torr. Kinetic evidence showed that the products ethylene and butenes were formed in both radical and molecular processes. Estimates of the rate constant k−1t and k−1c were, however, in reasonable agreement with the measurements of k1t and k1c. The mechanism of the ene reaction is discussed, and it is concluded that the transition state does not involve the formation of a biradical. Copyright © 1978 John Wiley & Sons, Inc.