T. Nauser et Re. Buhler, PIVALIC ACID AS COMBINED BUFFER AND SCAVENGER FOR STUDIES OF CLOUD-WATER CHEMISTRY WITH PULSE-RADIOLYSIS, Journal of the Chemical Society. Faraday transactions, 90(24), 1994, pp. 3651-3656
Citations number
26
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
The reactions of cloud water with transition-metal ions may be studied
using pivalic acid as buffer and .OH scavenger. Commonly used phospha
te buffers form strong complexes that may have an important effect on
reaction kinetics. Low solubility products limit transition-metal ion
concentrations to very tow levels (micromolar). With pivalic acid as b
uffer, we can increase the Cu-II concentration typically by a factor o
f 340. At the same time better buffer characteristics and less complex
formation is achieved. The scavenger efficiency equals that of tert-b
utyl alcohol. The rate data and the spectra of pivalic acid radicals h
ave been measured in N2O-saturated solutions of pivalic acid. The acid
constant was found to be 4.9 +/- 0.1. The rate constants for the reac
tion of .OH with pivalic acid have been re-evaluated: k[(CH3)(3)CCO2-
+ .OH] = (7 +/- 2) x 10(8) dm(3) mol(-1) s(-1) and k[(CH3)(3)CCO2H + .
OH] = 6.5 x 10(8) dm(3) mol(-1) s(-1). The importance of including rea
ctions like H. + .CH2(CH3)(2)CCO2H in the reaction model is shown. The
rate constants for the recombination of pivalic acid radicals are: k[
2.CH2(CH3)(2)CCO2H] = (7 +/- 1) x 10(8) dm(3) mol(-1) s(-1), k[.CH2(CH
3)(2)CCO2H + .CH2(CH3)(2)CCO2-] = (7 +/- 3)x 10(8) dm(3) mol(-1) s(-1)
and k[2.CH2(CH3)(2)CCO2-] = (3.7 +/- 0.4) x 10(8) dm(3) mol(-1) s(-1)
.