Intra- and Intermolecular Hydrogen Bonding of 2-Methoxyethanol and 2-Butoxyethanol in <i>n</i>-Hexane

Abstract

Glycol−ether compounds such as 2-methoxyethanol (CH3OCH2CH2OH) and 2-butoxyethanol [CH3(CH2)3OCH2CH2OH] 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.