Carbon acidity of the alpha-pyridinium carbon of a pyridoxamine analog.

Authors :: Crugeiras J
Rios A
Amyes TL
Richard JP
Source :: Organic & biomolecular chemistry [Org Biomol Chem] 2005 Jun 07; Vol. 3 (11), pp. 2145-9. Date of Electronic Publication: 2005 Apr 26.
Publication Year :: 2005
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.