Intra- and Intermolecular hydrogen bonding of 2-methoxyethanol and 2-butoxyethanol in n-hexane

Glycol-ether compounds such as 2-methoxyethanol (CH3OCH2CH2OH) and 2-butoxyethanol [CH3(CH2)(3)OCH2CH2OH] form both intra- and intermolecular hydrogen bonds. Using Fourier transform infrared spectroscopy, we have measured extent of intra-and intermolecular hydrogen bonding in these compounds dissolved in n-hexane at varying concentrations and temperatures. Intramolecular hydrogen bonds are present at all conditions, whereas intermolecular bonds appear at higher concentrations. Using lattice-fluid-hydrogen-bonding theory, equilibrium constants for the formation of intra- and intermolecular hydrogen bonds are determined. The results show that the equilibrium constant for intermolecular bond formation is approximately 6 times the intramolecular equilibrium constant for 2-methoxyethanol systems at 35 degrees C. Experiments at higher temperature, 45 degrees C, with 2-methoxyethanol show less hydrogen bonding as expected due to higher thermal energy. Due to steric hindrance, 2-butoxyethanol has a lower degree of hydrogen bonding than 2-methoxyethanol at the same temperature and concentration.