15min:

ARINDAM GANGULY, JOSHUA J. KLAASSEN, TODOR K. GOUNEV, JAMES R. DURIG, DEPARTMENT OF CHEMISTRY, UNIVERSITY OF MISSOURI-KANSAS CITY, KANSAS CITY, MO 64110,USA; GAMIL A. GUIRGIS, DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY, COLLEGE OF CHARLESTON, CHARLESTON, SC 29424, USA.

Variable temperature (-55 to -100 ^\circ\mathrmC) studies of the infrared spectra (4000-400 cm^-1) of bromocyclobutane, c-C₄H₇Br dissolved in liquid xenon have been carried out. The infrared spectrum (4000-100 cm^-1) of the gas has also been recorded. The enthalpy difference between the more stable equatorial conformer and the axial form, has been determined to be 372 \pm 34 cm^-1 . This experimental value of H is much lower than the average MP2(full) ab initio predicted value of 521 \pm 87 cm^-1. The percentage of the axial conformer present at ambient temperature is estimated to be 14 \pm 1%. By utilizing previously reported microwave rotational constants for the equatorial conformer combined with ab initio MP2(full)/6-311+G(d,p) predicted structural values, adjusted r₀ parameters have been obtained. The determined heavy atom structural parameters for this conformer are with distances(Å) C_ -Br = 1.942(3), C_ -C_ = 1.541(5), C_ -C_ = 1.552(3)Å and angles in degrees \angleC_ C_ Br = 118.4(5), \angleC_ C_ C_ = 89.7(5), \angleC_ C_ C_ = 86.8(5), \angleC_ C_ C_ = 88.9(5) and C_ C_ C_ C_ = 29.8(5) ^\circ. The results will be discussed and compared to the corresponding properties of some similar molecules.