Kinetics of base-catalyzed dehydrochlorination of hexachlorocyclohexanes: I. Homogeneous systems

Journal of Environmental Quality
Mingzhong RenXiangmei Liu

Abstract

Base-catalyzed dehydrochlorination of alpha-, beta-, and gamma-hexachlorocyclohexane (HCH) was examined at different pH and temperature conditions. No reaction was observed for beta-HCH under all tested conditions likely due to the fact that all chlorines are at the equatorial positions. Highly pH- and temperature-dependent reaction rates were observed for alpha- and gamma-HCH, and pentachlorocyclohexenes (PCCHs) and 1,2,4- and 1,2,3-trichlorobenzene (TCB) were detected as the intermediates and final products of the transformation of both alpha- and gamma-HCH. The pseudo-first-order rate constants of each step of the reactions were calculated at different T and pH conditions. For the first step, the rate constants were at approximately 0.0005 d-1 in solutions below pH 7.0, and increased by about an order of magnitude per pH unit from pH 7.01 to pH 12.02. The second-order reaction rate constants (kb) of this step were 3.57+/-0.03 and 3.19+/-0.19 M-1 d-1, respectively, and the associated activation energies (Ea) at pH 9.26 were 60.4+/-7.8 and 67.7+/-8.7 kJ mol-1, respectively, for alpha- and gamma-HCH. The rate constants for the formation of 1,2,3-TCB (k21) and 1,2,4-TCB (k22) were 0.0032+/-0.0001 d-1 and 0.051+/-0.003 d-1 from a...Continue Reading

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Citations

Sep 5, 2015·Environmental Science and Pollution Research International·Stanisław WacławekDaniel Elliott
Feb 26, 2015·Water Science and Technology : a Journal of the International Association on Water Pollution Research·M HomolkováM Černík
Oct 26, 2018·Environmental Science and Pollution Research International·Jirui YangXinhua Qi
Nov 18, 2010·Chemical Communications : Chem Comm·David R B BrittainColin J Jackson
Nov 30, 2019·International Journal of Molecular Sciences·Suraj KannathAgnieszka Dybala-Defratyka

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