Free radical addition to olefins. Part 4.—The light-induced addition of sulphur chloride pentafluoride to ethylene

Abstract

The light-induced addition of SF₅Cl to ethylene (E) has been studied in a series of gas-phase experiments in which concentration, relative light intensity and temperature have been varied. The results can be rationalized by the following chain mechanism in which the addition step (2) is appreciably reversible in the temperature range studied: SF₅Cl +hv → SF₅·+ Cl·(1) SF₅·+ E ⇌ SF₅E·(2), (–2) SF₃E·+ SF₅Cl → SF₅ECl + SF₅·(3) Cl·+ E → ECl·(4) ECl·+ SF₅Cl → ECl₂+SF₅·(5) SF₅·+ SF₅·→ S₂F₁₀(6) From a series of experiments in which both pressure and temperature were varied the following rate expressions were obtained. k₂/k^½₆=(3.9 ± 0.6) exp (–1,900 ± 200/RT)1.^½mole^–½ sec^–½,‡k_–2/k₃=(118 ± 20) exp (–6,660 ± 300/RT)1.^–1 mole.