title: The identification of vicinally substituted cyclohexane isomers in their mixtures by 1H and 13C NMR spectroscopy.
abstract: The radical addition reactions of organobromine compounds, XBr (X = CH2COOMe, PhCH2, CHBr2 and CCl3) with cyclohexene afforded mixtures of cis/trans isomer pairs of 1-X-2-Br-cyclohexanes. In addition to benzyl benzoyloxy derivatives are formed also, when benzoyl peroxide is used as an initiator. Owing to the great difficulties in separating these cis/trans isomer pairs, they are identified directly in their mixtures by NMR spectroscopy. In addition to one-dimensional (ID) 1H, proton decoupled 13C and DEPT-135, also two-dimensional (2D) 13C-13C INADEQUATE as well as 1H-13C HMQC experiments have been used in assigning the signals of each compound in their mixtures. The identification of each isomer was based on comparison of experimental 3J(H,H) coupling constants with theoretical ones based on the well-known Karplus type relationship. The more stable conformation for each isomer was estimated using the semiempirical AM1 molecular orbital method. The calculations support the isomer pair elucidations.
authors.affiliation: Department of Chemistry, University of Jyväskylä, Finland. laihia@jyu.fi
authors.forename: K
authors.initials: K
authors.lastname: Laihia
authors.forename: E
authors.initials: E
authors.lastname: Kolehmainen
authors.forename: T
authors.initials: T
authors.lastname: Nevalainen
authors.forename: R
authors.initials: R
authors.lastname: Kauppinen
authors.forename: T T
authors.initials: TT
authors.lastname: Vasilieva
authors.forename: A B
authors.initials: AB
authors.lastname: Terentiev
mesh_terms: D002247:Carbon Isotopes; D003510:Cyclohexanes / Q000032:analysis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D013237:Stereoisomerism; D014316:Tritium
chemical_list: D002247:Carbon Isotopes; D003510:Cyclohexanes; D014316:Tritium