ISSN:
0377-0486
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The Raman (3200 to 10 cm-1) and far-infrared (375 to 80 cm-1) spectra of gaseous bromocyclobutane, c-C4H7Br, have been recorded. A series of Q-branches observed in both of these spectra, beginning at 149 cm-1 with successive transitions falling to lower frequencies, have been assigned to the ring-puckering vibrations of both the low-energy equatorial and high-energy axial conformers. These data have been fit to an asymmetric potential function of the form V(cm-1) = (6.58 ± 0.21) × 105X4 - (3.27 ± 0.04) × 104X2 × (4.59 ± 0.19) × 104X3 with a reduced mass of 214 amu. Utilizing this potential, the difference between the puckering angles for the two conformers is calculated to be 6°, with the equatorial conformer having the larger value of 20°. Also from this potential function, the energy difference between the equatorial and axial forms is found to be 361 ± 20 cm-1 (1.03 kcal mol-1), with a barrier of 636 ± 20 cm-1 (1.82 kcal mol-1) to interconversion. Experimental values for the enthalpy difference between the two conformers have been determined for both the liquid (297 ± 27 cm-1) and gas (∼ 350 cm-1) from relative intensities of a pair of Raman lines over 90 and 58 °C temperature ranges respectively. These results are compared to the corresponding quantities for some similar molecules.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jrs.1250201202
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