Vibrational spectra, normal coordinate calculations, and molecular mechanics calculations for 3-methyl-1-hexyne and 5-methyl-1-hexyne

Abstract

IR and Raman spectra were obtained for 3-methyl-1-hexyne and 5-methyl-1-hexyne. The spectra were interpreted with the aid of normal coordinate calculations. Molecular mechanics calculations were made for all possible conformers of each compound. 3-Methyl-1-hexyne existed mainly in one stable conformation (C7C3C4C5C6 coplanar), but smaller amounts of several other conformers were present. 5-Methyl-1-hexyne existed mainly as two conformers, but smaller amounts of three others were probably present. Vibrational assignments, force constants, and MM2 structural parameters are given.