Methyl yield from radiolysis

The branching of the adduct decomposition was studied by measuring the pKa of the mixtures. Thus for pulse radiolysis of N20-saturated methyl phenyl sulfoxide the results yield a p/Ca obs value of 1.50 while the values for methane sulfinic and benzene sulfinic acids are 2.28 and 1.29, respectively. The fraction of each branch can be calculated from the equation,... 

The ESR study of solids at low temperatures can yield evidence for primary photochemical processes involving radical production. Svejda and Volman (353) have obtained ESR evidence for two primary photochemical processes of CH CN one involves a C-C bond scission, the other involves a C-H bond split. They further substantiated the C-H split mechanism by observing the ethylidenimino radical (CH )HC=N, resulting from the addition of the H atom to CH CN. The photochemistry of CH CN appears rather simple compared to the radiolysis of CH CN in which methyl radicals are produced by photochemical reactions in the y-irradiated sample (354). Recently Sprague and Williams (355) have demonstrated that methyl radicals produced from CH CN in a low-temperature glass can abstract hydrogen... 

The effect of electrical fields on the radiolysis of ethane has been examined by Ausloos et and this study has shown that excited molecules contribute a great deal to the products. The experiments were conducted in the presence of nitric oxide, and free-radical reactions were therefore suppressed. The importance of reactions (12)-(14) was clearly demonstrated by the use of various isotopic mixtures. Propane is formed exclusively by the insertion of CH2 into C2H6 and the yield is nearly equal to the yield of molecular methane from reaction (14). Acetylene is formed from a neutral excited ethane, probably via a hot ethylidene radical. Butene and a fraction of the propene arise from ion precursors while n-butane appears to be formed both by ionic reactions and by the combination of ethyl radicals. The decomposition of excited ethane to give methyl radicals, reaction (15), has been shown by Yang and Gant °° to be relatively unimportant. The importance of molecular hydrogen elimination has been shown in several studies ° °. ... 

Radiolysis of liquid cresols under vacuum was found to produce H2 as the main gaseous product the radiolytic yield varied from 0.019 for m-cresol to 0.031 (rmol for the o-cresol. Small amounts of CH4 were also detected. Radiolysis of cyanophenols produced less H2, only ca 0.003 ttmol various yields of CO and CO2, mainly from the ortho isomer, and minute amounts of N2. The difference in the yield of H2 may be due to reaction of hydrogen atoms with the methyl group of the cresols to form H2 as compared with addition to the CN group and to the ring, which do not produce H2. No mechanistic details were derived from these studies. 

Deoxycytidinyl)methyl radical (98) was produced from the respective phenyl sulfide (99) via 254 nm photolysis. Initial studies in dinucleotides revealed that 98 adds to the C8-position of dG to form intrastrand cross-linked products (Scheme 41). These products were also observed when 98 was generated from 99 in chemically synthesized oligonucleotides, and when DNA was subjected to y-radiolysis. In DNA, 100 is favored over 101 and is even detected, albeit in almost 20-fold lower yield when 98 is generated under aerobic conditions. 

In the radiolysis of liquid n-alkanes both the yields of hydrogen (G 0.5 pmol J ) and C-C bond decompositions ( 0.17 xmol J ) remain essentially constant when the carbon atom number increases from C4 to C17. It should be noted that neither the C-H nor the C-C breaks occur randomly. The frequency of C-H decompositions at the secondary carbon atoms is 3 times more frequent than at the primary carbons. The fragmentation of the carbon skeleton occurs preferentially in its central region, elimination of the methyl group is relatively infrequent (Holroyd 1968 Gyorgy 1981 Wojnarovits and Schuler 2000). 

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