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Stereochemical effects in the gas-phase pinacol rearrangement. 2. Ring contraction versus methyl migration in cis- and trans-1,2-dimethylcyclohexane-1,2-diol

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00212a017· OSTI ID:5419481
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The gas-phase pinacol rearrangement of cis- and trans-1,2-dimethylcyclohexane-1,2-diols, promoted by D/sub 3//sup +/, CH/sub 5//sup +//C/sub 2/H/sub 5//sup +/ and t-C/sub 4/H/sub 9//sup +/ ions, was studied by mass spectrometric and radiolytic methods in the pressure range 0.5-760 Torr. When product isomerization is inhibited, by using N(CH/sub 3/)/sub 3/ as a trapping reagent at high pressure, mixtures of 2,2-dimethylcyclohexanone and 1-acetyl-1-methylcyclopentane were recovered from the reaction. In methane, the trend of the measured relative rates for ring contraction (k/sub 5/), methyl or hydroxyl group migration (k/sub 6/) versus the rearrangement rate of pincaol itself (k/sub p/), is k/sub 6/(trans) approx. k/sub 5/(trans) greater than or equal to k/sub 5/(cis) > k/sub 6/(cis) greater than or equal to k/sub p/. No evidence for the formation of an intermediate carbenium ion was found. Stereochemical aspects of the mechanism are discussed and compared with solution data.

Research Organization:
Universita di Roma La Sapienza, Italy
OSTI ID:
5419481
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:4; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400600 -- Radiation Chemistry
ALCOHOLS
ALKANES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
CYCLOALKANES
DATA
DECOMPOSITION
DEUTERIUM COMPOUNDS
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
FLUIDS
GAMMA RADIATION
GASES
GLYCOLS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
IONIZING RADIATIONS
KINETICS
LOW PRESSURE
MASS SPECTROSCOPY
MEDIUM VACUUM
NUMERICAL DATA
ORGANIC COMPOUNDS
PINACOL
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADIOLYSIS
REACTION KINETICS
SPECTROSCOPY
STEREOCHEMISTRY