The Trialkylhydrazyl-Trialkylhydrazine Radical Cation Proton Transfer. 1. Equilibrium Constant

Article abstract of DOI:10.1021/ja00537a034

Pulse radiolytically generated e_aq^- and *C(CH3)2OH in water reduce trialkyldiazenium salts (R3N2⁺) to hydrazyl radicals (R3N2*), which protonate to give hydrazine radical cations (R3N2H⁺*).Determination of pK_a (R3N2H⁺*) by conductivity measurements gave 7.0 (+/- 0.4), 8.3 (+/- 0.2), and 10.4 (+/- 0.2) for the radical cations of 2-tert-butyl 2,3-diazabicyclo<2.2.1>heptane (1H⁺*), its 7-spirocyclopropyl analogue (2H⁺*), 2-tert-butyl-2,3-diazabicyclo<2.2.2>octane (3H⁺*), and 9-tert-butylamino-9-azabicyclo<3.3.1>nonane (4H⁺*), respectively.The respective values for pK_a (R3N2H2⁺) - pK_a (R3N2H⁺*) are +2.1, +2.4, +1.2, and -2.6.The hydrazyl radical and hydrazine radical cation have similar absorption spectra except for system 4, where a significant red shift in UV maximum of the hydrazyl relative to that of the hydrazine radical cation was observed.The deviant behavior of the N,N-cycloalkyl compound 4 from the N,N'-cycloalkyl compounds 1 - 3 is argued to result from 4* being more twisted about the NN bond than 4H*, while such twisting does not occur in the N,N'-cycloalkyl systems.