Absolute rate constants (k) for reduction of substituted methylperoxyl radicals by ascorbate ions and by TMPD [N,N,-A'.N'-tetramethyl-p-phenylenediamine) in aqueous solutions have been determined by pulse radiolysis. The rate constants vary from 106 to 109 M"1 s'1, increasing as the electron-withdrawing capacity of the substituent on the peroxyl group increases.Linear correlations are observed between log k and the Taft substituent constants * for a wide variety of substituents, but not all substituents fit the same line. In the case of ascorbate as reductant, the points for peroxyl radicals that contain halogens on the -carbon lie on a different line (p* = 0.41) than that for the other substituents (p* = 1.25). In the case of TMPD there are also two families of peroxyl radicals: those comprising the electron-donating groups Me through -Bu (p* = 5.6) and those containing electron-withdrawing substituents (p* = 0.64).

Rate constants have been measured by pulse radiolysis for the reactions of the NO, radical with five cyclic ethers and a series of alcohols. Rate constants ranged from 3.5 x lo4 M-' 5 -l for deuterated methanol to 1.1 x lo7 M-' 5-l for tetrahydrofuran. The rate constants for the reactions of NO3 with the alcohols 1-propanol to 1-heptanol were found to be linearly dependent on the number of CH2 groups with a group reactivity of 6.4 x lo5 M-' s-'.

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