Synthetic, structural, spectroscopic, and stopped-flow kinetic investigation of imine production

Synthetic and formation kinetics studies have been made of imine production from the reaction of 3-methyl-2-thiophenecarboxyaldehyde with 3-(1H-imidazol-1-yl) propan-1-amine (L-1), 1-(3-aminopropyl) pyrolidin-2-one (L-2), 2-piperazin-1-ylethanamine (L-3) and 2-hydrazinopyridine (L-4). Kinetics were determined by rapid reaction techniques using absorbance changes at multi wavelengths in methanol. Activation enthalpies for imine formation in methanol vary from 101 to 121 kJ mol(-1) and entropies of activation (DS not equal) vary from -98 to -188 J K-1 mol(-1). All of these observations are indicative of an S(N)2 mechanism. Activation parameters of the reactions were calculated under second-order reaction conditions. The analysis of kinetic data in solutions was performed with the SPECFIT/32 software package which provides useful information on the binding characteristics of functional groups and mechanism of the reactions. The crystal structure of 3-methylthiophene-2-carbaldehyde pyridine-2-ylhydrazone is described.