Hydrolysis kinetics of 2-cyanopyridine, 3-cyanopyridine, and 4-cyanopyridine in high-temperature water

We report herein the kinetic studies on hydrolysis of three cyanopyridines in high-temperature water. 3-Cyanopyridine, 4-cyanopyridine and 2-cyanopyridine underwent consecutive hydrolysis to the corresponding pyridinecarboxamides and picolinic acids. Further decarboxylation to pyridine was observed for 2-cyanopyridine hydrolysis. Experiments at different initial reactant concentrations revealed that these compounds exhibited the first-order kinetics. Experiments at different temperatures showed that the first-order rate constants displayed an Arrhenius behavior with activation energies of 74.3, 40.3, and 83.7 kJ mol-1 for 3-cyanopyridine, 4-cyanopyridine, 2-cyanopyridine, respectively. The activation energies obtained for 3-pyridinecarboxamide, 4-pyridinecarboxamide and 2-pyridinecarboxamide hydrolysis are 80.1, 32.7, and 70.5 kJ mol-1, respectively. The effect of substituent position on activation energies for cyanopyridine and pyridinecarboxamide hydrolysis is ortho approximate to meta > para. (c) 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 641648, 2012