Redi, Mesfin (PhD)Tsegazab, Yisak (Mr)Mohammed, Ali2019-10-072023-11-092019-10-072023-11-092018-05-05http://etd.aau.edu.et/handle/12345678/19316Rotational barrier in nicotinamide and picolinamide have been investigated employing temperature-dependent proton nuclear magnetic resonance (1H NMR) spectrometry. In nicotinamide and picolinamide the two protons on the nitrogen appeared at different chemical shift positions revealing that they are magnetically non-equivalent. In the experiments, nicotinamide showed two distinct peaks corresponding to the amine group of the amide molecule, and the peak separation decreased as a function of temperature indicating a rotational barrier about the amide bond. The coalescence of the two peaks was observed at 328 K. Using through line shape analysis of the temperature dependent spectra; a rotational barrier of 17.9 kcal mol −1was calculated. Interestingly the opposite temperature dependence of the peak separation was observed in picolinamide in which the separation increased as the temperature was increased and no convergence was observed in the temperature ranges the experiments were conducted. The observed behaviour clearly demonstrates that the splitting of the peaks cannot be attributed to the rotational barrier about the C−N bond rather it suggests that the two peaks originate from two different chromophores (O−H and =N−H chromophores) resulting from a tautomeric equilibrium.en1H NMRNicotinamidePicolinamideRotational BarrierRate ConstantThesis