Optical rotatory dispersion studies. 132. Conformational isotope effect in deuterium-substituted cyclohexanones

Journal Article · Tue Jan 27 23:00:00 EST 1981 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00392a008· OSTI ID:6603754

Lee, S F; Barth, G; Djerassi, C

The observed temperature dependence of the circular dichroism spectra of (3R)-2,2-dimethyl-3-deuteriocyclohexanone (1), (4S)-2,2-dimethyl-4-deuteriocyclohexanone (2), and (5S)-2,2-dimethyl-5-deuteriocyclohexanone (3) is interpreted as reflecting a conformational isotope effect which biases the equilibrium of the two chair conformers toward that conformation in which the deuterium substituent is axially oriented. With use of the estimates for the rotational strengths of the involved conformers as obtained from sterochemically rigid reference compounds, energy differences of -9.5, -4.2, and -2.7 cal/mol were calculated for the equilibria of 1, 2, and 3, respectively. Empirical force field calculations show that the configuration of 2,2-dimethylcyclohexanone is slightly distorted from the symmetrical chair form. With use of the smaller nonbond interaction for C...D and H...D, energy differences were calculated for 1, 2, and 3 which are in qualitative agreement with the experimental ones.

• Research Organization: Stanford Univ., CA
• OSTI ID: 6603754
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 103:2; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
CYCLOHEXANONE
DEUTERIUM
DEUTERIUM COMPOUNDS
DICHROISM
ENERGY LEVELS
EXCITED STATES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
KETONES
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
OPTICAL ACTIVITY
ORGANIC COMPOUNDS
ROTATIONAL STATES
STABLE ISOTOPES
STEREOCHEMISTRY
TEMPERATURE DEPENDENCE