Kinetics and mechanism of the oxidation of (. cap alpha. -hydroxyalkyl)chromium complexes by copper(II) and iron(III) ions

Journal Article · Wed May 20 00:00:00 EDT 1981 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00400a040· OSTI ID:6232187

Bakac, A; Espenson, J H

Copper(II) and iron(III) ions react with (..cap alpha..-hydroxyalkyl)chromium(2+) complexes (alkyl = methyl, ethyl, 2-propyl) in water or in aqueous alcohol solutions leading to the cleavage of the chromium-carbon bond. The immediate products are Cr/sup 2 +/, the reduced metal ion (Cu/sup +/ or Fe/sup 2 +/), and the corresponding aldehyde or ketone. The reactions obey the rate law -d(CrROH/sup 2 +/)/dt = (k + k'(H)/sup -1/(CrROH/sup 2 +/)(M), where M = Cu/sup 2 +/ or Fe/sup 3 +/. The dominant k' term has the following values in 1 M aqueous parent alcohol (methanol, ethanol, and 2-propanol, respectively): CrCH/sub 2/OH/sup 2 +/, k'/sub Cu/ = 0.251 s/sup -1/,k'/sub Fe/ = 0.496 s/sup -1/; CrCH(CH/sub 3/)OH/sup 2 +/, 1.46, 0.481; CrC(CH/sub 3/)/sub 2/OH/sup 2 +/, 0.574, 1.90. The reactivity toward Cu/sup 2 +/ and Fe/sup 3 +/ is significantly diminished upon substitution of the OH hydrogen by an alkyl group. Copper(II) does not react with (..cap alpha..-alkoxyalkyl)chromium(2+) complexes at all, while iron(III) shows some reactivity with k'/sub Fe/ = 0.0127 s/sup -1/ (CrCH/sub 2/OCH/sub 3//sup 2 +/) and 0.0400 s/sup -1/ (CrCH(CH/sub 3/)OC/sub 2/H/sub 5//sup 2 +/), both in 1 M methanol. A mechanism proposed for the oxidation of (..cap alpha..-hydroxyalkyl)chromium(2+) complexes by copper(II) and iron(III) consists of the oxidant attack at the alcoholic OH group followed by a slow electron-transfer step.

• Research Organization: Ames Lab., IA
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 6232187
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 103:10; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ALCOHOLS
AQUEOUS SOLUTIONS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM COMPLEXES
COMPLEXES
COPPER COMPOUNDS
DATA
DISPERSIONS
EXPERIMENTAL DATA
HYDROXY COMPOUNDS
INFORMATION
IRON COMPOUNDS
KINETICS
MIXTURES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OXIDATION
REACTION KINETICS
REDUCTION
SOLUTIONS
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS