ESR study of the photolysis ofnhyphen;butyl iodide: Secondary photolysis and structure of thenhyphen;butyl radical

摘要

The photolysis ofnhyphen;butyl iodide in argon at 4thinsp;deg;K has been studied as a function of photon energy and photolysis time, using electron spin resonance (ESR) spectroscopy to detect the free radical products. Photolysis at 2790 Aring; gives only thenhyphen;butyl radical, but photolysis at 2460 Aring; yields hydrogen atoms and some methyl radicals in addition tonhyphen;butyl. Thenhyphen;butyl yield is approximately proportional to photolysis time for photolysis at 2460 Aring;, but the H atom and CH3yields have a stronger than linear dependence on photolysis time suggesting that these species are produced by secondary photolysis of thenhyphen;butyl radical. The magnetic constants ofnhyphen;butyl, determined from its ESR spectrum, are:g1=2.0029,g2=2.0030,g3=2.0025;A(agr;)1= minus;29,A(agr;)2= minus;18,A(agr;)3= minus;21 Oe; andA(bgr;1)0= 46.5,A(bgr;2)0= 21.3 Oe. Axis 1 is parallel to the Cagr;Cbgr;bond. Axis 3 is perpendicular to the agr;hyphen;CH2plane and lies approximately in the plane determined by the Cagr;Cbgr;bond and bgr;hyphen;CH bond of the bgr;hyphen;proton having the 46.5 Oe isotropic hyperfine splitting constant. The magnetic constant data also indicates that the agr;hyphen;CH2group has considerable freedom for torsional oscillation about this equilibrium position.