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Thermodynamic and kinetic analysis of the dimerization of aqueous glyoxal
Author(s) -
Fratzke Alfred R.,
Reilly Peter J.
Publication year - 1986
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550180705
Subject(s) - chemistry , glyoxal , dimer , ionic strength , depolymerization , reaction rate constant , aqueous solution , monomer , equilibrium constant , catalysis , ionic bonding , kinetics , polymer chemistry , organic chemistry , ion , polymer , physics , quantum mechanics
Equilibria and rates of interconversion between monomeric and dimeric glyoxal were measured in aqueous solution. The equilibrium constant [ G 2 ]/[ G 1 ] 2 was 0.56 M −1 at 25°C, and was hardly affected by changes of ionic strength and pH but increased rapidly with increase of temperature. The rate of depolymerization was first‐order in dimer, with the pseudo first‐order rate coefficient in the pH range 1.3–7.8being of the form b 1 [H 3 O + ] + b 2 + b 3 [OH − ]/(1 + b 4 [OH − ]) + b 5 [OH − ]. Coefficients b 1 and b 2 were more strongly affected by changes of temperature, though [OH − ] was much the more effective catalyst. This rate form has not previously been observed for monomer‐dimer inter‐conversion of α‐hydroxycarbonyls and α‐dicarbonyls or for related reactions such as mutarotations and hydrations. Equivalent rate forms arisefrom reactions where an intermediate at steady state and low concentration is produced.