Infrared study of the hydrogen bond complexes between N-methylsuccinimide and phenols

The hydrogen bonded complexes between N-methylsuccinimide and phenols (pKa = 10.2 --> 6) are investigated by infrared spectrometry. The thermodynamic parameters for the 1-1 complexes are determined in carbon tetrachloride. The formation constants at 298 K range from 15 to 150 dm(3) mol(-1), the enthalpies of complex formation from -20 to -30 kJ mol(-1), the changes of entropy from -22 to -40 J K-1 mol(-1) and the frequency shifts of the nu(OH) stretching vibration from 170 to 340 cm(-1). The complexes are weaker than those involving the monocarbonyl bases. The decrease of the force constant of the bonded carbonyl group ranges from 0.48 to 0.65 N cm(-1). The force constant of the free C=O group slightly increases upon complex formation, in agreement with the cooperativity theory.