Research on Chemical Intermediates

, Volume 31, Issue 1–3, pp 113–133 | Cite as

Ionization of mercapto- and hydroxypyridines by free electron transfer to alkyl chloride parent radical cations

  • Devidas B Naik
  • Ralf Hermann
  • Tulsi Mukherjee
  • Sergej Naumov
  • Ortwin Brede
Article

In the pulse radiolysis of solutions of 2-mercaptopyridine (2-PySH) and 2-hydroxypyridine (2-PyOH) in n-butyl chloride, as well as 4-mercaptopyridine (4-PySH) and 3-hydroxypyridine (3-PyOH) in 1,2-dichloroethane, radical cations (PySH˙+ and PyOH˙+) are generated in the electron transfer reaction from solute to parent solvent radical cations exhibiting rate constants (1–2) × 1010 dm3 mol−1 s−1. The solute radical cations decay within less than 100 up to 200 ns, yielding pyridinethiyl radicals (PyS˙) or pyridoxyl radicals (PyO˙), respectively. Quenching the solvent cation radicals with ethanol, it is observed that the resulting radicals, e.g., Cl-CH2-CH˙ -Cl radicals, react with 3-PyOH by addition. In the presence of ethanol, radicals formed by deprotonation of the solvent radical cations react with mercaptopyridine resulting in pyridinethiyl radicals PyS˙(k about 1× 109 dm3 mol−1 s−1). With parent 4-PySH, 4-mercaptopyridinethiyl radicals undergo an equilibrium-like dimerization reaction where k = 900 dm3 mol−1 was determined. Quantum chemical calculations support our mechanistic interpretations and provide information about the charge distribution and the reactivity of the radical cations and radicals described.

PYRIDINE IONIZATION ELECTRON TRANSFER KINETICS DFT 

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© VSP 2005

Authors and Affiliations

  • Devidas B Naik
  • Ralf Hermann
  • Tulsi Mukherjee
  • Sergej Naumov
  • Ortwin Brede

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