Hydride transfer in the oxidation of alcohols by (bpy)/sub 2/(py)Ru(O))/sup 2 +/. A k/sub H//k/sub D/ kinetic isotope effect of 50

Conference · Wed Feb 04 04:00:00 EST 1987 · J. Am. Chem. Soc.; (United States)

OSTI ID:6889668

Roecker, L; Meyer, T J

The kinetics of oxidation of a series of alcohols by ((bpy/sub 2/(py)Ru/sup IV/(O))/sup 2 +/ (bpy is 2,2'-bipyridine and py is pyridine) have been studied in aqueous solution and in acetonitrile. The reactions are first order in both alcohol and Ru/sup IV/ = O/sup 2 +/, pH independent from pH 1.0 to 6.8, and slightly slower in acetonitrile than in water. Rate constants for oxidation increase with substituent as follows: methyl < primary < secondary < allylic less than or equal to benzylic. Tertiary alcohols are unreactive, and in the series of para substituted benzylic alcohols, X-C/sub 6/H/sub 4/CH/sub 2/OH (X = CH/sub 3/O, CH/sub 3/, H, F, Cl, CF/sub 3/, and NO/sub 2/), the rate of oxidation is relatively insensitive to the substituent X. In aqueous solution k ranges from (3.5 +/- 0.1) x 10/sup -4/ M/sup -1/ s/sup -1/ for the oxidation of methanol (..delta..H/sup double dagger/ = 14 +/- 2 kcal/mol, ..delta..S/sup double dagger/ = -26 +/- 6 eu) to 2.43 +/- 0.03 M/sup -1/ s/sup -1/ for the oxidation of benzyl alcohol (..delta..H/sup double dagger/ = 5.8 +/- 0.4 kcal/mol, ..delta..S/sup double dagger/ = -38 +/- 1 eu). Large C-H kinetic isotope effects are observed, but solvent isotope effects are negligible. For CH/sub 3/OH compared to CD/sub 3/OH, k/sub H//k/sub D/ = 9 at 25/sup 0/C and for benzyl alcohol, C/sub 6/H/sub 5/CH/sub 2/OH compared to C/sub 6/H/sub 5/CD/sub 2/OH, k/sub H//k/sub D/ = 50 +/- 3 at 25/sup 0/C. Spectral evidence, in conjunction with the isotope effect data, suggests that oxidation of alcohols by ((bpy)/sub 2/(py)Ru/sup IV/(O))/sup 2 +/ occurs by a two-electron, hydride transfer.

• Research Organization: Univ. of North Carolina, Chapel Hill
• OSTI ID: 6889668
• Conference Information: Journal Name: J. Am. Chem. Soc.; (United States) Journal Volume: 109:3
• Country of Publication: United States
• Language: English

Related Subjects

090210* -- Alcohol Fuels-- Properties-- (1976-1989)
10 SYNTHETIC FUELS
ACETONITRILE
ALCOHOLS
AQUEOUS SOLUTIONS
AZINES
BIPYRIDINES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
DATA
DEUTERIUM COMPOUNDS
DISPERSIONS
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
ISOTOPE EFFECTS
KINETICS
MIXTURES
NITRILES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
PYRIDINES
REACTION KINETICS
RUTHENIUM COMPLEXES
SOLUTIONS
TRANSITION ELEMENT COMPLEXES