Handbook of Solvents - George Wypych - ChemTech - Ventech!

4.1 Simple solvent characteristics 111
This approach has become a constituent of the Hansen approach and has not received a
separate development.
Polar interactions can themselves be divided into two types:
• Polar interactions where molecules having permanent dipole moments interact in
solution with the dipole orientation in a symmetrical manner. It follows that the
geometric mean rule is obeyed for orientation interactions and the contribution of
dipole orientations to the cohesive energy and dispersion interactions.
• Polar interactions accompanied by the dipole induction. These interactions are
asymmetrical.
Thus for a pure polar liquid without hydrogen bonds: 10
2 2 2
δ = δ + δ + 2δ
δ
d or d in [4.1.16]
where:
δd dispersion contribution to the solubility parameter
δor orientation contribution to the solubility parameter
δin induction contribution to the solubility parameter.
A more traditional approach of contribution of the induction interaction was published
elsewhere; 11 however, it was used only for the estimation of the common value of the δparameter
rather than for evaluation of solubility:
δ = δ + δ + δ
2 2 2 2
d p i [4.1.17]
The first method taking into account the hydrogen bonding was proposed by
Beerbower et al., 12 who expressed hydrogen bonding energy through the hydrogen bonding
number Δν. The data for various solvents were plotted into a diagram with the solubility parameter
along the horizontal axis and the hydrogen bonding number Δν along the vertical
axis. Data were obtained for a given polymer for suitable solvents. All solvents in which a
given polymer was soluble got a certain regions. Lieberman also plotted two-dimensional
graphs of solubility parameters versus hydrogen-bonding capabilities. 13
On the base of work by Gordy and Stanford, the spectroscopic criterion, related to the
extent of the shift to lower frequencies of the OD infrared absorption of deuterated methanol,
was selected. It provides a measure of the hydrogen-bonding acceptor power of a solvent.
14,15 The spectrum of a deuterated methanol solution in the test solution was compared
with that of a solution in benzene and the hydrogen-bonding parameter was defined as
where:
γ =Δ ν/10
[4.1.18]
Δν OD absorption shift (in wavenumber).
Crowley et al. 16 used an extension of this method by including the dipole moment of
the solvents. One of the axis represented solubility parameter, the second the dipole moment,
and the third hydrogen bonding expressed by spectroscopic parameter γ. Because this
method involved an empirical comparison of a number of solvents it was impractical. Nelson
et al. 17 utilized this approach to hydrogen bond solubility parameters. Hansen (see the
next section) developed this method.
18
Chen introduced a quantity χH