Radiolysis of dichloromethane (DCM) leads to formation of primary oxidizing radicals and carbon-centered radicals. The latter react with oxygen to yield peroxyl radicals. The yields and chemical behavior of these intermediates were studied by pulse radiolysis of DCM solutions containing various solutes: phenols, anilines, dimethoxybenzene, hexamethylbenzene, cyclohexene, dimethyl sulfoxide, and zinc tetratolylporphyrin. At low concentrations, some of these solutes were found to be oxidized by two peroxyl radicals, CH2C102* and CHC1202', with different rate constants. At higher concentrations, the solutes react also with the primary radicals: Cl atoms and the radical cations CH2C12+", with diffusion-controlled rate constants.The rates of these reactions were determined by competition kinetics because of the very short lifetimes of the species. Cl atoms were found to have a half-life of about 5 ns in DCM, reacting predominantly with the solvent by hydrogen abstraction. The radical cations decay within a fraction of a nanosecond. The total yield of these primary radicals was determined to be G = 3.6 and appears to be divided about equally between Cl and the radical cations. The total yield of oxidation, by the primary and the peroxyl radicals, was found to be G = 7.5. Cl atoms were found to be very reactive in electron transfer as well as addition and hydrogen abstraction reactions.

In basic aqueous solution the N3• radical is found to oxidize aromatic systems such as aniline and phenoxide ions and their derivatives at rate constants of (3-5) X 109 M"1 s"1. In contrast to the reactions of OH radicals, where addition to the ring dominates, oxidation appears to be directly by electron transfer. Compounds such as benzene, toluene, and anisóle are not observably oxidized by N3. Phenol, in its neutral form in acidic solution, is oxidized several orders of magnitude more slowly than is the phenoxide anion. The rate of oxidation of phenols is strongly dependent on substitution, with activating groups increasing the rate in the order para > ortho > meta. 3• can be readily prepared radiolytically by OH oxidation of azide.Being a neutral radical which does not absorb significantly above 300 nm it is very promising as a selective oxidant for pulse radiolysis studies.

Electrospray ionization mass spectrometry is used to detect both the cations (C+) and the anions (A-) of ionic liquids (CA). In this study, the ionic liquids are diluted with aqueous methanol before injection. In addition to the main peaks of the parent ions, fragmentation products are observed upon increasing the cone voltage, whereas aggregates of the parent ion with one or more ionic liquid molecules (e.g., C(CA)(n)(+), A(CA)(n)(-)) are observed upon decreasing the cone voltage. The ions of several ionic liquids in a mixture are also detected and the ratios of their concentrations estimated. A method is developed to determine quantitatively the concentration of an ionic liquid in solution by using the cation and anion of another ionic liquid as internal standards. By using this method, the solubilities in water at room temperature (22+/-1 degrees C) of three typical hydrophobic ionic liquids have been determined: 0.70+/-0.08 g L(-1) for methyltributylammonium bis(trifluoromethylsulfonyl)imide (MeBu(3)NNTf(2)), 6.0+/-0.5 g L(-1) for butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyrNTf(2)), and 18.6+/-0.7 g L(-1) for 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF(6)).

4156for the adduct + 0, reaction include the following: J. Phys. Chem. 1986, 90, 4156-4158 in both studies. At oresent, there is insufficient information to -CH3SCH30H + O2 -CH3S(0)CH3 + HOz (1 7a)CH3SOH is probably converted to CH3S03H (methanesulfonic acid) by reaction with Oz while the atmospheric fate of Me2S0 is unclear. MezSO has a very low vapor pressure and may be rapidly removed via heterogeneous processes.At 298 K our results demonstrate that reaction 1 in 1 atm of air proceeds 70% via abstraction and 30% via (irreversible) addition. Photooxidation studies have been reported by Niki et al.23 and Hatakeyama and A k i m o t~,~~ where SO2 yields from OHinitiated oxidation of CH3SCH3 were reported to be 22% and 21%, respectively. Large yields of methanesulfonic acid were observed allow SOz productioi to be associated with either the abstraction route or the addition route. However, it should be noted that our results suggest that abstraction is the dominant reaction pathway for T > 300 K while addition is the dominant pathway for T < 270 K. Hence, temperature-dependent product analysis studies should shed some light on the detailed pathways for SO2 and CH3S03H production. Acknowledgment.We thank R. J. Thompson for helping with some of the FP-RF experiments, J. K. Lawson for assistance in the data analysis, and J. M. Nicovich for helpful discussions and assistance in the data analysis. We also thank H. Niki for communicating to us his unpublished results on the HOZ + CH3SCH3 reaction.Rate constants for the reactions of CIOz, NOz, and SO3-radicals with several substituted phenoxide ions have been measured by pulse radiolysis. They vary from the immeasurably slow (lo9 M-' s-l) and depend on the redox potentials of the phenoxide ions and the inorganic radicals. With the weak oxidant SO; reverse reactions were observed in certain cases; i.e., the phenoxyl radical oxidizes sulfite ions. An attempt is made to correlate the rate constants with Hammett's substituent constants and the results are compared with those obtained previously for the reactions of various inorganic radicals with phenols and phenoxide ions.