Charge-transfer complexes in the scavenging by iodine of radicals formed on pulse radiolysis of cyclo hexane

Pulse radiolysis of solutions of iodine in cyclo hexane resulted in the formation of a transient absorption with wavelength maximum at 3300 Å. This transient spectrum was assigned to the C 6 H 12 ... I' charge-transfer complex. The spectrum and extinction coefficients of the complex over the wavelength range 2500 to 6500 Å were obtained, the coefficient at 3300 Å being 2025 1. mole -1 cm -1 . Hydrogen iodide in cyclo hexane gave rise to the same transient absorption. Pulse radiolysis of cyclo hexane and cyclo hexyl iodide alone gave rise to different transient spectra attributed to the cyclo hexyl radical, absorbing in the ultraviolet, extinction coefficient 3401. mole -1 cm -1 at 2550 Å and the C 6 H 11 .. .I* charge-transfer complex, absorption maximum 3900 A, extinction coefficient ~ 10 3 to 10 4 1. mole -1 cm -1 , respectively. During the course of the investigations rate constants were obtained for the following reactions: C 6 H 11 + I 2 C 6 H 11 I + I', k II = 7 x 10 9 1. mole -1 s -1 , 2C 6 H 12 ...I' -> 2C 6 H 12 + I 2 , k II = 1.06 x 10 10 1. mole -1 s -1 , or 21' -> I 2 , a C 6 H 10 + C 6 H 12 2C 6 H 11 k 11a + k 11b =2.5 x 10 9 1. mole -1 s -1 bC 12 H 22 Dilute solutions of iodine (10 -4 M) in cyclo hexane yielded experimental evidence for neutral radical intermediates only. There were, however, indications that ionic radical intermediates occur in more concentrated solutions ( > 10 -3 M).