Conformational stability of bromocyclohexane from temperature dependent FT-IR spectra of xenon solutions, r0 structural parameters and vibrational assignment

Conformational stability from variable temperature infrared spectra of xenon solution, r0 structural parameters, and vibrational assignment of fluorocyclohexane

“…The assignment for most of the modes which are carbon-hydrogen vibrations have frequencies very similar to the corresponding modes for the corresponding vibrations for chlorocyclohexane [2] and bromocyclohexane [3]. However for these other two halogen substituted cyclohexanes only a few of the C-H modes could be clearly identified in the vapor state for the axial conformer.…”

“…These results indicate the value should be near 100 cm À1 (0.29 kcal/mol) but theoretical predictions from molecular mechanics (MM) calculations [8] give a value of 67 cm À1 (0.19 kcal/mol) whereas from MP2 ab initio calculations [9] a value of 33 cm À1 (0.09 kcal/mol) was obtained. Therefore these results do not provide a value which can be easily compared with the enthalpy values recently obtained for chloro- [2] and bromocyclohexane [3]. For this reason we have again determined the DH of fluorocyclohexane from infrared spectra of variable temperature studies of xenon solutions.…”

“…The first of these studies was the determination of the DH differences for the conformers of chlorocyclohexane [2] and bromocyclohexane [3] from temperature variations of the infrared spectra of xenon solutions. The determined DH values are 132 ± 13 cm À1 (1.08 ± 0.11 kcal/mol) for the chlorocyclohexane and 239 ± 24 cm À1 (1.94 ± 0.20 kcal/mol) for bromocyclohexane with ab initio predicted values of 161 ± 18 cm À1 (1.31 ± 0.14 kcal/mol) and 168 ± 22 cm À1 (1.37 ± 0.17 kcal/mol), respectively.…”

Conformers, electronic states, and diabolical conical intersections in the valence photoelectron spectroscopy of halocyclohexanes

“…Neutral C 6 H 11 X (X = Cl, Br, and I) has previously been studied by, e.g., electron diffraction; 30,31 nuclear magnetic resonance (NMR); 32,33 and microwave, [34][35][36][37] Raman, 38,39 and IR spectroscopies. [40][41][42][43][44] The conformational equilibrium was also investigated computationally. 45,46 These studies focused mainly on the conformational energy and have shown that the population of axial conformer is 23%-45% for C 6 H 11 Cl, 18%-30% for C 6 H 11 Br, and ≈26% for C 6 H 11 I at ambient temperature, meaning that the axial and equatorial conformers are nearly isoenergetic.…”

Conformational stability, infrared and Raman spectra, vibrational assignments, and theoretical calculations of cyclohexylamine

“…The investigation of six-membered rings with non-substituted cyclohexane started in our laboratory by studying the relative intensities of the Raman active fundamentals and the potential function governing the conformational interchange between the chair and twisted boat form [3]. Studies were initiated to spectroscopically investigate monosubstituted chloro- [4], bromo- [5] and fluorocyclohexane [6] to further understand the conformational stability of the chair form, since there are only two conformers, equatorial and axial forms, which exist at ambient temperature. Due to the repulsive non-bonded nature of the interaction between the axial and the equatorial substituent, the equatorial conformation is generally favored according to two study reported previously [2,7] and these monosubstituted cyclohexanes exist mostly in the equatorial form.…”