FAR-INFRARED SPECTRA, CONFORMATIONAL EQUILIBRIUM, BARRIERS TO INTERNAL-ROTATION, VIBRATIONAL ASSIGNMENT AND AB-INITIO CALCULATIONS OF 2-FLUOROETHANOL

The far infrared spectrum (370 to 50 cm(-1)) of gaseous 2-fluoroethano l has been recorded at a resolution of 0.10 cm(-1). The fundamental as ymmetric torsion of the more stable gauche (Gg') conformer (relative o rientation around the C-C bond) where the fluorine and oxygen atoms ar e gauche to one another has been observed at 150 cm(-1). For the high energy trans (Ttl conformer the fundamental asymmetric torsional mode and accompanying excited states are assigned to a series of Q branches in the region of 81 to 69 cm(-1). From these data the potential funct ion for internal rotation around the C-C bond of the FCH2 asymmetric t op has been determined and the potential coefficients are: V-1 = 263+/ -16, V-2 = -542+/-16, V-3 = 1132+/-5, and V-4 = -198+/-2 cm(-1). The t rans to gauche, gauche to gauche, and gauche to trans barriers have be en determined to be 643, 1753 and 1005 cm(-1), respectively, with an e nthalpy difference between the conformers of 362+/-48 cm(-1) (1.04+/-0 .14 kcal/mol). The structural parameters, conformational stabilities, barriers to internal rotation and fundamental vibrational frequencies which have been determined experimentally, are compared to those obtai ned from ab initio Hartree-Fock gradient calculations employing the RH F/3-21G, RHF/6-31G* and RHF/6-31++G** basis sets, and to the correspo nding quantities obtained for some similar molecules.