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Reactions of the ferryl ion with some compounds found in cloud water
Author(s) -
Jacobsen Frank,
Holcman Jerzy,
Sehested Knud
Publication year - 1998
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/(sici)1097-4601(1998)30:3<215::aid-kin7>3.0.co;2-v
Subject(s) - chemistry , reaction rate constant , dissociation (chemistry) , ion , bond dissociation energy , electron transfer , hydrolysis , acid dissociation constant , inorganic chemistry , medicinal chemistry , analytical chemistry (journal) , kinetics , aqueous solution , organic chemistry , physics , quantum mechanics
The lifetime of the ferryl ion FeO 2+ , (minutes at pH below 1) is reduced by a factor of 50 at pH above 3. This is rationalized in terms of an acid‐base equilibrium between two different hydrolytic forms of this species (Fe(OH) ++ 2 and Fe(OH) + 3 ) with a p K a =2.0. The rate constants for reactions between FeO 2+ and selected compounds found in cloud water were measured in acid solutions by stopped‐flow technique. For inorganic reactants: k HNO2 =1.1×10 4 M −1 s −1 , k NO2− ≤10 5 M −1 s −1 , k Cl− =1.0×10 2 M −1 s −1 , k HSO3− =2.5×10 5 M −1 s −1 , k SO2 =4.5×10 5 M −1 s −1 , and k Mn(II) =1.0×10 4 M −1 s −1 were obtained and for the organic reactants: k HCOOH =160 M −1 s −1 , k HCOO− =3×10 5 M −1 , k CH3COOH =3.1 M −1 s −1 , k CH2(OH)2 =400 M −1 s −1 , k CH3COCH3 =16 M −1 s −1 , k CH3CH20H =2.5×10 3 M −1 s −1 , k C6H5OH =4.0×10 3 M −1 s −1 , and k C6H5COOH =80 M −1 s −1 were obtained. A good correlation between log( k ) and the standard one electron reduction potential ( E °) indicates that the reactions of inorganic compounds proceed by electron transfer. The reaction mechanisms in case of organic compounds are very similar to the reactions of the OH radical, i.e., H‐abstraction, and a fairly good correlation between log( k ) and the bond dissociation energy BDE was obtained. Activation parameters were measured for the reaction of FeO 2+ with HNO 2 ( E a =34.5 kJ/mol); Mn 2+ ( E a =21.3 kJ/mol); HCOOH ( E a =22.3 kJ/mol); CH 2 (OH) 2 ( E a =44.5 kJ/mol); and C 6 H 5 OH ( E a =28.1 kJ/mol). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 215–221, 1998.