title: Carbon acidity of the alpha-pyridinium carbon of a pyridoxamine analog.
abstract: We report second-order rate constants of kDO = 120 dm(3) mol(-1) s(-1) and kB = 6.4 x 10(-4) dm(3) mol(-1) s(-1) for exchange for deuterium of the first alpha-methylene proton of the 4-(aminomethyl)pyridine dication in D2O at 25 degree C and I= 1.0 (KCl). These data are consistent with a carbon acid pKa between 17 and 19 for ionization of this simple carbon acid and they show that the effect of an alpha-pyridinium substituent on carbon acidity is similar to that of an alpha-ester substituent.
authors.affiliation: Departmento de Química Física, Universidad de Santiago, 15706 Santiago de Compostela, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Crugeiras
authors.forename: Ana
authors.initials: A
authors.lastname: Rios
authors.forename: Tina L
authors.initials: TL
authors.lastname: Amyes
authors.forename: John P
authors.initials: JP
authors.lastname: Richard
mesh_terms: D002244:Carbon / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D011726:Pyridinium Compounds / Q000737:chemistry*; D011733:Pyridoxamine / Q000737:chemistry*
chemical_list: D011726:Pyridinium Compounds; D011733:Pyridoxamine; D002244:Carbon