Conformer-specific ionization spectroscopy of bromocyclohexane: equatorial versus axial conformers.
Ionization of equatorial and axial conformational isomers of the chair-bromocyclohexane is investigated with use of the vacuum ultraviolet mass-analyzed threshold ionization (MATI) spectroscopic technique. Two distinct ionization energies of 9.8308 ± 0.0025 and 9.8409 ± 0.0025 eV are determined for equatorial or axial conformers, respectively. From the conformer-selective vibrational analysis, it is found that the equatorial conformer undergoes a drastic structural change upon ionization especially along the C-Br distortion mode, whereas the axial conformer shows the modest change along the ring-puckering mode with ionization, corresponding to the reaction coordinate for the conformational interconversion. Density functional theory (DFT) calculations with and without considering the spin-orbit coupling provide the appropriate mode assignments for the vibrational bands active in the ionization spectra. Natural bond orbital (NBO) analysis is carried out to give insights into the contribution of the anomeric effect to the structure-energy relationship in each conformational isomer.
Han
Songhee
S
Department of Chemistry and KI for Nanocentury, KAIST, Daejeon 305-701, Korea.
Yoo
Hyun Sik
HS
Kim
Sang Kyu
SK
D003510:Cyclohexanes / Q000737:chemistry*; D013058:Mass Spectrometry; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
D003510:Cyclohexanes