Physical and structural studies of N-carboxymethyl- and N-(p-methoxyphenyl)-3-hydroxy-2-methyl-4-pyridinone

Abstract

3-Hydroxy-1-carboxymethyl-2-methyl-4-pyridinone (Hcmp) and 3-hydroxy-1-(p-methoxyphenyl)-2-methyl-4-pyridine (Hpap) have been prepared and studied by single crystal X-ray diffraction. Crystals of Hemp are monoclinic, a = 6.340 (2), b = 7.705 (1), c = 16.226 (1) Å, β = 94.74 (1), Z = 4, space group P21/n and those for Hap are monoclinic, a = 10.8435 (9), b = 16.680 (2), c = 13.5665 (6) Å, β = 109.450 (4), Z = 8, space group C2/c. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to R = 0.030 and 0.041 (Rw = 0.039 and 0.058) for 1642 and 1819 reflections with I ≥ 3σ(I), respectively. Bond lengths and bond angles in the two compounds are normal; however, Hcmp forms as a zwitterion in the solid state. The two compounds were also studied by mass spectrometry, UV, infrared, proton NMR spectroscopies, and potentiometric equilibrium measurements. The protonation constants for Hcmp are log K1 = 9.76 (1), log K2 = 3.43 (1), and log K3 = 2.78 (3) and for Hpap are [Formula: see text] and [Formula: see text]. Keywords: 3-hydroxy-4-pyridinone, zwitterion, hydrogen bonding, protonation constant, crystallography, solid state.