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General-acid-catalyzed reactions of hypochlorous acid and acetyl hypochlorite with chlorite ion.
MedLine Citation:
PMID:  11197017     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
The rate of oxidation of ClO2- by HOCl is first order in each reactant and is general-acid catalyzed. In the initial steps of the proposed mechanism, a steady-state intermediate, HOClOClO-, forms (k1 = 1.6 M-1 s-1) and undergoes general-acid (HA)-catalyzed reactions (k2HA) to generate a metastable intermediate, ClOClO. Values of k2HA/k-1 are 1.6 x 10(4) M-1 (H3O+), 20 M-1 (HOAc), and 8.5 M-1 (H2PO4-). Subsequent competitive reactions of ClOClO with ClO2- (k3) to give 2ClO2 and with OH- (k4OH) and other bases (k5B) to give ClO3- are very rapid. The relative yields of these products give k4OH/k3 = 1.3 x 10(5), k5HPO4/k3 = 0.20, and k5OAc/k3 = 0.06. At low pH and low buffer concentrations, the apparent yield of ClO2, based on 2ClO2 per initial HOCl, reaches 140%. This anomaly is attributed to the induced disproportionation of ClO2- by ClOClO to give ClO3- and additional HOCl. A highly reactive intermediate, ClOCl(O)OClO-, is proposed that can undergo Cl-O bond cleavage to give 2ClO2 + Cl- via one path and ClO3- + 2HOCl via another path. The additional HOCl recycles in the presence of excess ClO2- to give more ClO2. Ab initio calculations show feasible structures for the proposed reaction intermediates. Acetic acid has a second catalytic role through the formation of acetyl hypochlorite, which is much more reactive than HOCl in the transfer of Cl+ to ClO2- to form ClOClO.
Authors:
Z Jia; D W Margerum; J S Francisco
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Inorganic chemistry     Volume:  39     ISSN:  0020-1669     ISO Abbreviation:  Inorg Chem     Publication Date:  2000 Jun 
Date Detail:
Created Date:  2001-01-24     Completed Date:  2001-03-01     Revised Date:  2003-10-31    
Medline Journal Info:
Nlm Unique ID:  0366543     Medline TA:  Inorg Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2614-20     Citation Subset:  -    
Affiliation:
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
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