Infrared spectroscopy of the symmetric branched isomers of n-heptanol

Three pure heptanol isomers were studied using infrared spectroscopy: n-heptanol, 2,4-dimethyl-3-pentanol, and 3-ethyl-3-pentanol. In order to analyze the branching effect of heptanol, investigations on the two symmetric branched isomers have been performed. Branching and steric hindrance highly influence the aggregation in associating systems. Therefore, a systematic comparison with the linear molecule n-heptanol is performed to better understand the experimental data. The vibrational structures were studied in the spectral range from 650 to 4000cm−1 and the individual peaks were assigned to the corresponding vibrational modes of the molecules. The OH-stretching band is significantly narrower in the spectra of the branched alcohols compared to n-heptanol. In particular, the low frequency components of the band are absent. This is a result of the steric hindrance leading to a less pronounced hydrogen bonding network.