A kinetic study of the reaction between formic acid and HOBr

Abstract

The reaction between formic acid and HOBr in strongly acid aqueous media was studied by absorption spectrophotometry at 298 K. Bromine, the monitored species, displays a transient behavior, gradually rising up to a maximum and then decaying with first-order kinetics. Reaction rates, expressed as R = -dC_(Br_2)/dt, depend on the concentrations of HCOOH (0.1–1.4M), HOBr (0.3–1.5 × 10^(−3)M), and H^+ (0.1–1.0M). The mechanism (1) HOBr + HCOO^- = Br^- + CO_2 + H_2O (2, -2) H^+ + Br^- + HOBr ⇌ Br_2 + H_2O (3) Br_2 + HCOO^- = 2Br^- + CO_2 + H^+ with k_1 =1.04 ± 0.20M^(−1) · s^(−1), k_3 = 20.2M^(−1), quantitatively accounts for all observations within experimental error.

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