The Raman (3500-10 cm-') and infrared (3500-50 cm-') spectra of gaseous and solid n-propylamine, CH,CH,CH,NH, , and its deuterated analog, CH,CH,CH,ND, , were recorded. Additionally, the Raman spectra of the liquids were measured and qualitative depolarization values were obtained. From the fact that several distinct Raman lines disappear on going from the fluid phases to the solid state, it is concluded that the molecule exists as a mixture of several conformers, with the trans-trans conformer being the most stable form in the solid. The first term indicates the position of the methyl group relative to the CN bond, whereas the second term indicates the position of the lone electron pair on the nitrogen relative to the central CC bond Relying mainly on group frequencies, depolarization data and relative intensities of Raman and infrared bands, a complete vibrational assignment is proposed for the trans-trans conformer. Ab initio calculations were carried out on these molecules, employing both 3-21G and 6-31G* basis sets. The results obtained using these basis sets are compared, and used in normal coordinate calculations. The results of the ab initio calculations support the vibrational assignment, and also indicate that it is the trans-trms and trans-gauche conformers which are the more stable forms of npropylamine and have nearly equal energies. ~~~

The asymmetric torsional potential function of n-butane has been redefined based on a combination of results obtained from experimental and theoretical calculations. From the vibrational spectra of gaseous n-butane below 500 cm-' the asymmetric torsional fundamentals of the more stable s-trans and high-energy gauche conformations of n-butane have been assigned at 121.28 and 116.60 cm-', respectively, each with excited states falling to lower frequencies, Additionally, from variable-temperature studies of the Raman spectra for n-butand, and d , , , the conformational enthalpy difference has been determined to be 381 f 41 cm-' (1089 f 117 cal mol-') and 369 f 72 cm-' (1055 & 206 cal mol-I), respectively. Optimized structural parameters, obtained from ab initio methods, for the s-trans and gauche conformers have been used to allow for structural relaxation during the asymmetric internal rotation and to place constraints on the determined potential function. The resulting potential coefficients are V , = 584 f 7, V, = -96 f 7, V, = 1165 & 3, V , = 45 f 3, V, = -3 f 2 and V, = -40 + 1 and the s-trans to gauche, gauche to gauche and gauche to s-trans barriers are determined to be 1274, 1370 and 891 cm-', respectively, with an enthalpy difference between the conformers of 383 2 17 cm-' (1095 f 49 cal mol-I).This potential function is consistent with a dihedral angle for the gauche conformer of 65.4". Additionally, this potential has a 'syn' barrier, which is the energy difference between the s-trans minimum and the gauche to gauche transition state, of 1753 cm-I (5.01 kcal mol-'), which is in excellent agreement with the most recent value of 1836 cm-' (5.25 kcal mol-') obtained from a very high-level ab i n i h calculation. In order to provide a more complete description of the normal vibrational modes of n-butane, normal coordinate analyses have been completed for n-butane-do, -d, and -dlo based on force constants from ab initio calculations. The infrared (3500-40 cm-') and Raman (3500-10 cm-') spectra of n-butane-d, and -dlo have been obtained and complete vibrational assignments are provided. The structural parameters, conformational stabilities, barriers to internal rotation and vibrational frequencies which have been determined experimentally are compared with those obtained by ab initio methods.

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