ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The equilibrium constant for the reaction CH2(COOH)2 + I3- ⇆ CHI(COOH)2 + 2I- + H+, measured spectrophotometrically at 25°C and ionic strength 1.00M (NaClO4), is (2.79 ± 0.48) × 10-4M2. Stopped-flow kinetic measurements at 25°C and ionic strength 1.00M with [H+] = (2.09-95.0) × 10-3M and [I-] = (1.23-26.1) × 10-3M indicate that the rate of the forward reaction is given by (k1[I2] + k3[I3-]) [HOOCCH2COO-] + (k2[I2] + k4[I3-]) [CH(COOH)2] + k5[H+] [I3-] [CH2(COOH)2]. The values of the rate constants k1-k5 are (1.21 ± 0.31) × 102, (2.41 ± 0.15) × 101, (1.16 ± 0.33) × 101, (8.7 ± 4.5) × 10-1M-1·sec-1, and (3.20 ± 0.56) × 101M-2·sec-1, respectively. The rate of enolization of malonic acid, measured by the bromine scavenging technique, is given by ken[CH2(COOH)2], with ken = 2.0 × 10-3 + 1.0 × 10-2 [CH2(COOH)2]. An intramolecular mechanism, featuring a six-member cyclic transition state, is postulated to account for the results on the enolization of malonic acid. The reactions of the enol, enolate ion, and protonated enol with iodine and/or triodide ion are proposed to account for the various rate terms.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550090108
