KINETICS AND MECHANISM OF THE OXIDATION OF DL-HOMOSERINE BY CR-VI

The oxidation of homoserine by Cr-VI in acidic medium yields 2-amino-4 -oxobutyric acid and Grill as the final products when a 60-fold or hig her excess of substrate over Cr-VI is used, The redox reaction occurs through a Cr-VI --> Cr-IV --> Cr-II a Grill path, The complete rate la w for the Cr-VI oxidation reaction is expressed by -d[Cr-VI]/dt = {k(0 ) + k [H+][homoserine]}[Cr-VI], where k(0) = (6 +/- 2) x 10(-5) s(-1) and k = (2.5 +/- 0.1) x 10(-3) M-2 s(-1) at 30 degrees C. Evidence for Cr-II, formed in a fast step, is obtained from CrO22+ absorption band s at 290 and 245 nm, The maximum [CrO22+] represents up to 65% oi the total chromium concentration, when [Cr-VI](0) s 0.016 mM. The mechanis m and the associated reaction kinetics are presented and discussed.