Intra- and Intermolecular Hydrogen Bonding of 2-Methoxyethanol and 2-Butoxyethanol in n-Hexane

Glycol−ether compounds such as 2-methoxyethanol (CH 3 OCH 2 CH 2 OH) and 2-butoxyethanol [CH 3 (CH 2 ) 3 OCH 2 CH 2 OH] 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 °C. Experiments at higher temperature, 45 °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.