CHARACTERISTIC PARAMETER METHOD - I - THE RMOKINETIC RESEARCH METHOD OF SIMPLE ORDER REACTIONS

A linear-fitting method for measuring the cooling constant of a thermo kinetic system has been proposed in this paper. The cooling constants of thermokinetic systems of the reaction of nitroethane with tris(hydr oxymethyl) aminomethane in 1mol . L-1 KCl aqueous solution and saponif ication of ethyl butyrate in omega = 0.85 aqueous ethanol have been me asured with this method at 15, 30, and 45 degrees C, respectively. The results show that the cooling constants measured with this method hav e good reproducibility and self-adaptability, and are in good agreemen t with those measured with steady-state peak-height method. Therefore, the linear-fitting method for measuring cooling constants is believed to be correct. The effects of temperature,medium, concentrations of r eactants and sample-feeding manner on the cooling constant of a thermo kinetic system have also been discussed. The results show that medium and sample-feeding manner have great effects on the cooling constant. Nevertheless,the relative error of the cooling constant is only about 1% when the initial concentrations of reactants vary onefold at the sa me temperature and in the same solvent to a same reaction. Based on th e basic theory of thermokinetics proposed in the literatures, a novel research method of thermokinetics which can be applied to study slow a nd fast reactions,the characteristic parameter method,has been develop ed in this paper. The general formulas for calculating kinetic paramet er K-n and rate constants k(n) have been derived. In order to test the validity of this novel method, the saponification of ethyl acetate, e thyl propionate and ethyl benzoate, the formation of hexamethylenetetr amine and the polymerization of acrylamide, have been studied. Atl the experimental results are in good agreement with those in the literatu res, and therefore the characteristic parameter method has been proved valid.