A SPECTROPHOTOMETRIC KINETIC-STUDY OF THE REACTION OF AMINO-ACIDS WITH P-BENZOQUINONE

The rates of the reaction of the amino acids with p-benzoquinone were investigated as a function of pH, temperature and the basicity of the amino group. In consideration of the different equilibria of the amino acids species in solution, and under the assumption that the neutral and the anion are the most reactive species, reacting with the rate co nstant k(z) and k(A) respectively, the suggested kinetic equation is: k(2) = k(z)/K-D+k(A)K(2)/[H+], where k(2) is the observed second order rate constant, k(z) and k(A) are the second order rate constants asso ciated with neutral and anion species of the amino acids. K-2 is the s econd ionization constant of the amino group of amino acid, K-D is the equilibrium constant between the Zwitterion and the neutral species o f the amino acids. Linear relationship between logk(A) and pK(2) of th e tested amino acids was obtained. The activation parameters as well a s the mechanism of the reaction have been already discussed.