KINETICS OF FORMATION OF N-PYRUVYLIDENEGLYCINATOZINC (2) ZINC (2) CATALYSIS UNDER APPROXIMATELY NEUTRAL CONDITIONS

The rate of reaction of pyruvate (P) with glycinate (G−) in the presence of Zn(II), pH range 4.5-7.6, ionic strength 0.5, 25°, is described by the rate law: d(ZnPG)/dt = KPG(P−)(G−) + KHPG (H+)(P−)(G−) + KZnPG·(Zn2+)(P−)(G−) + KZnPGH(Zn2+)(P−)(G−)(H+) + KZNPG2(Zn2+)(P−)(G−)2, where KPG = 0.15 M−1 sec−1, KHPG = 9.2 × 107 M−2 sec−1, KZNPG = 3.4 × 103 M−2 sec−1, KZNPGH = 1.03 × 109 M−3 sec−1, and KZNPG2 = 3.4 × 107 M−3 sec−1 In these reactions Zn(II) appears to play a promnastic role rather than serve as a template; i.e., the metal ion brings the ligands into proximity by forming a labile ternary complex but imposes a minimum geometric constraint upon them. © 1969, American Chemical Society. All rights reserved.