Hydrogen bonding with aromatic rings

Abstract

Thermodynamic effects of hydrogen bonding are important in determining the phase behavior in polar fluids. While efforts to understand “strong” donor and “strong” acceptor combinations (H‐bonds involving a formation energy more negative than −20 kJ/mol such as alkanol‐alkanol H‐bonding have been substantial, weak H‐bonds involving double bonds or aromatic rings as proton acceptors) have largely been ignored. Using FTIR spectroscopy H‐bonding between alcohol donor and aromatic ring‐containing acceptor molecules was studied including l‐hexanol and cyclohexanol at low concentrations where self‐association is negligible (strong donors). H‐bonding “weak” acceptors studied include toluene and m‐xylene. Clear spectroscopic evidence existed for the formation of H‐bonds between the alcohol and aromatic molecules, which are much weaker than conventional “strong donor”–“strong acceptor” H‐bonds. Using quantitative FTIR measurements, the percentage of H‐bonded alcohol molecules over a range of aromatic concentrations was determined. Ab initio calculations also showed that alcohol–aromatic H‐bonds are much weaker than alcohol–alcohol H‐bonds. This H‐bonding, though weak, will contribute significantly to the chemical potential of the molecules.

Mutual solubilities of hydrocarbons and water with the CPA EoS

“…Although the aromatic hydrocarbons are themselves non-self-associating, it is well known that aromatic compounds are able to cross associate (solvate) with water [37,38,63]. A solvation scheme involving combining rules for the cross-associating energy and volume parameters [30] was here employed.…”

“…For the aromatics compounds a single association site is considered, cross associating with water, as suggested by some theoretical and experimental evidence [37,38].…”

The Effect of Water on the Microstructure of 1‐Butyl‐3‐methylimidazolium Tetrafluoroborate/TX‐100/Benzene Ionic Liquid Microemulsions

“…[52] Free and hydrogen-bonded species have molecular vibrations at different IR frequencies. [51] Therefore, FTIR spectroscopic analysis is the most widely used method to investigate the states of solubilized water and the structures of traditional aqueous microemulsions.…”

Thermodynamic Stability Analysis of Tolbutamide Polymorphs and Solubility in Organic Solvents

“…All the solvents are able, at least to some extent, to accept hydrogen bonds, although acetonitrile is a comparatively weak electron donor, as is the aromatic ring of toluene. [12] Neither toluene nor ethyl acetate are able to donate protons, however. Out of these two solvents, ethyl acetate shares a stronger chemical similarity with the tolbutamide molecule, having a polar group in the center surrounded by non-polar regions.…”