Ionization in Liquid Ammonia of Methyl and Amino Groups Bonded to Pyridine and Pyrazine. A Method of Determining Their pKa Values
Journal of Organic Chemistry
Proton magnetic resonance spectra of ionized 2-methyl and 2-amino derivatives of pyridine and pyrazine along with spectra of 2-pyridone and 2-pyrazinone in liquid ammonia are reported. Changes in chemical shifts produced by ionization of the pyridines are linearly related to those for the pyrazines. Competition experiments show that 2-methyl- is less acidic than 4-methylpyridine; estimates of the pK, values for these two acids are given. It is suggested that the results provide a basis for determining the equilibrium acidities of weak heterocyclic acids.
ionization, liquid ammonia, pyridine, pyrazine
Helmick, L. S. (1973). Ionization in Liquid Ammonia of Methyl and Amino Groups Bonded to Pyridine and Pyrazine. A Method of Determining Their pKa Values. Journal of Organic Chemistry, 38, 658-662.