Conformational analysis, tautomerization, IR, Raman, and NMR studies of 3-phenylazo-2,4-pentanedione

Harmonic vibrational frequencies of this stable hydrazo form and its deuterated analog were also calculated and compared with the experimental data. According to the theoretical calculations, the intramolecularly hydrogen bonded proton in the most stable tautomer moves in an asymmetric double minimum potential with a hydrogen bond stronger than that of 4-amino-3-penten-2-one (APO). The calculated O· · ·N distance for the most stable conformer of PAPD is about 0.07-0.08 Ǻ shorter than that of APO.