Gradual solvation of protons by water is observed in liquids by mixing strong mineral acids with various amounts of water in acetonitrile solutions, a process which promotes rapid dissociation of the acids in these solutions. The stoichiometry of the reaction XH(+) + n(H(2)O) = X + (H(2)O)(n)H(+) was studied for strong mineral acids (negatively charged X, X = ClO(4)¯, Cl¯, Br¯, I¯, CF(3)SO(3)¯) and for strong cationic acids (uncharged X, X = R*NH(2), H(2)O). We have found by direct quantitative analysis preference of n = 2 over n = 1 for both groups of proton transfer reactions at relatively low water concentrations in acetonitrile. At high water concentrations, we have found that larger water solvates must also be involved in the solvation of the proton while the spectral features already observed for n = 2, H(+)(H(2)O)(2), remain almost unchanged at large n values up to at least 10 M of water.

The reduction, catalytic reduction and the electrocatalytic reduction of halo‐organic compounds are of major interest due to their role as pollutants. The mechanism and kinetics of reduction of 2,2‐dibromomethyl‐1,3‐propanediol by several NiI tetraazamacrocyclic complexes, (NiILi)+ (i = 1−4), in aqueous solutions to yield Br− and the non‐halogenated compound was studied using the pulse radiolysis technique. The rate constants k = 5.3 × 108, 1.6 × 107, 6.0 × 105 and 3.5 × 104 M−1s−1 for L1, L2, L3 and L4 respectively, of the reactions (NiILi)+ + RBr ⇄ (NiIILi)2+ + Br− + R· increase with the free‐energy gain in the reaction. All these complexes are good electrocatalysts for the reduction of this substrate. The mechanisms of the reductions is are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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Radical Catalyzed Debromination of Bromo-Alkanes by Formate in Aqueous Solutions via a Hydrogen Atom Transfer Mechanism. -(SHANDALOV, E.; ZILBERMANN, I.; MAIMON, E.; NAHMANI, Y.; COHEN, H.; ADAR, E.; MEYERSTEIN*, D.; Tetrahedron Lett. 45 (2004) 5, 989-992; Dep. Chem., Ben Gurion Univ. Negev, Beer-Sheva 84105, Israel; Eng.) -Staver 20-040