Reaction of hydrogen peroxide with the oxochromium(IV) ion by hydride transfer

Journal Article · Wed Jul 07 04:00:00 EDT 1993 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00066a030· OSTI ID:5999036

Al-Ajlouni, A M; Espenson, J H; Bakac, A ^[1]

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1. Iowa State Univ., Ames (United States)

Oxidation of hydrogen peroxide by pentaaquaoxochromium(IV), (H[sub 2]O)[sub 5]CrO[sup 2+], in aqueous acidic solutions (0.10-1.0 M HClO[sub 4]) yields the superoxochromium(III) ion (H[sub 2]O)[sub 5]CrOO[sup 2+]. The same product is obtained in both the presence and the absence of oxygen. In 0.10 M HClO[sub 4] the second-order rate constant at 25[degrees]C is 190[+-]10 L mol[sup [minus]1] s[sup [minus]1] in O[sub 2]-saturated solutions and 172[+-]8 L mol[sup [minus]1] s[sup [minus]1] in Ar-saturated solutions, independent of acidity and ionic strength in the range 0.10-1.0 M (HClO[sub 4]/LiClO[sub 4]). In D[sub 2]O a solvent the rate constant is k[sub D] = 53[+-]3 L mol[sup [minus]1] s[sup [minus]1], resulting in the kinetic isotope effect k[sub H]/k[sub D] = 3.6. Experiments in the temperature range 6.8-38.4[degrees]C yielded [delta]H = 25[+-]kJ mol[sup [minus]1] and [delta]S = [minus]116[+-]8 J mol[sup [minus]1] K[sup [minus]1]. A hydride-transfer mechanism is suggested for the oxidation of H[sub 2]O[sub 2] by CrO[sup 2+]. It involves the coordination of H[sub 2]O[sub 2] to Cr(IV) prior to the hydride abstraction step. The reaction of HCrO[sub 4][sup [minus]] with H[sub 2]O[sub 2] under the same conditions also yields (H[sub 2]O)[sub 5]CrOO[sup 2+], which was identified by its characteristic UV spectrum. Possible mechanisms for these reactions are discussed.

• OSTI ID: 5999036
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 32:14; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ABSORPTION SPECTRA
ACTIVATION ENERGY
ARRHENIUS EQUATION
CATIONS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
ENERGY
EQUATIONS
HYDRIDES
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
IONS
ISOTOPE EFFECTS
KINETICS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PEROXIDES
PHYSICAL PROPERTIES
REACTION KINETICS
SPECTRA
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS