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 ≈ meta > para. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 641–648, 2012