Far infrared and low frequency gas phase Raman spectra, vibrational assignment, and conformational stability of 1-chloro-2-methylpropane and 1-bromo-2-methylpropane

Molecular Mechanics (MM3) Conformational Studies of Cyclic and Acyclic Monochloroalkanes

“…Isobutyl chloride exists as two stable conformers, trans and gauche . From the temperature-dependent gas phase Raman spectrum of isobutyl chloride, Durig et al and 0.15 kcal/mol by Nomura et al …”

“…Isobutyl chloride exists as two stable conformers, trans and gauche. From the temperature-dependent gas phase Raman spectrum of isobutyl chloride, Durig et al 5 calculated the enthalpy difference (∆H) between the gauche and trans conformers to be 0.48 kcal/mol, with the trans conformer being higher in energy, which is more than the previously reported values: 0.22 kcal/mol by Wyn-Jones et al 6 and 0.15 kcal/mol by Nomura et al 7 Ab initio calculations 8 using the 4-31G basis set gave 0.38 kcal/mol of the energy difference (∆E). MM3 correctly gives the gauche isomer to be 0.28 kcal/mol (∆H) and 0.18 kcal/mol (∆E) more stable than trans form.…”

Transferable Scaling Factors for Vibrational Force Fields of Halogenated Molecules Based on Energy-Consistent Pseudopotentials

“…Because most vibrations of bromine and iodine can be found in the spectral region below 600 cm -1 , there are not very many studies in which these particular modes have been securely assigned. Thus, the training set used comprises the following 36 molecules: methyl bromide, bromoform, bromoethylene, 2,3-dibromopropene, acetyl bromide, 3-bromopropene, 1-bromo-2-methylpropane, bromobenzene, all- cis -1,2-dimethyl-3-bromocyclopropane, dibromomaleic anhydride, o -bromotoluene, propionyl bromide, 2-bromofuran, p -bromonitrobenzene, bromocyclohexane, p -bromotoluene, N -bromosuccinimide, 2,5-dibromofuran, p -bromophenol, bromocyclopentane, 1-bromopropane, methyl iodide, iodoethylene, trans -diiodoethylene, cis -diiodoethylene, p -iodonitrobenzene, iodocyclopentane, allyl iodide, 2-iodofuran, iodoethane, o -diiodobenzene, p -diiodobenzene, o -iodotoluene, p -iodotoluene, N -iodosuccinimide, and 2-iodopropane. , It was found to be necessary to introduce four new scaling factors for each halogen (Hal). These correspond to X−Hal stretchings, XY−Hal bendings and two kinds of torsions, where X and Y denote C, N, or O atoms.…”