32817-38-2Relevant articles and documents
Acid-Base Kinetics of Pyridine Studied with a Slow Spectrophotometric Indicator in Methanol
Marshall, David B.,Eyring, Edward M.,Strohbusch, Frank,White, Robert D.
, p. 7065 - 7067 (2007/10/02)
The protonation-deprotonation kinetics of pyridine in methanol has been studied by the electric field jump technique.Kinetic measurements of the electric field insensitive equilibrium B + H+ (k1) BH+ (k-1), where B denotes pyridine, were obtained by coupling the equilibrium with a field-sensitive, visibly colored indicator equilibrium.Use of the "slow" indicator 2,2',4,4',6,6'-hexanitrodiphenylamine allowed observation of the slower of the two relaxation times of the coupled system in a time range where measurements could be made with sufficient precision for a reliable extraction of the rate constants k1 and k-1 from the data.The values obtained are k1 = 1.57 +/- 0.32 * 1010 dm3mol-1s-1 and k-1 = 8.43 +/- 1.69 * 104 s-1.The value for k1 is within the expected limits for a diffusion-controlled reaction in this solvent.An ionic reaction radius of 3.9 Angstroem is calculated from the protonation rate constant value, which indicates that the neutral species involved is probably a hydrogen-bonded pyridine-methanol complex rather than free pyridine.The value for k-1 is 1 order of magnitude greater than the constant for methyl-substituted pyridines, reflecting unsubstituted pyridine's lower basicity in methanol.
