Handbook of Solvents - George Wypych - ChemTech - Ventech!

4.1 Simple solvent characteristics 115
δd nD
= 955 . −555
. [4.1.30]
where:
nD refractive index
Alternatively Keller et. al. 35 estimated that for nonpolar and slightly polar liquids
where:
δ d
= 62. 8x
for x ≤ 0.28 [4.1.31]
2 3
δd =− 4. 58 + 108x − 119x + 45x
for x > 0.28 [4.1.32]
n
x =
n
2
D
2
D
− 1
+ 2
Peiffer suggested the following expression: 35
( 4 3 )( 1)
2 2
δ = K ππI
/ d N / V
[4.1.33]
d
3
where:
K packing parameter
I ionization potential
α molecular polarizability
N number of molecules in the volume unit
V1 =Nr* 3 /K
r* the equilibrium distance between molecules.
For the estimation of nonpolar component of δ Brown et al. 36 proposed the
homomorph concept. The homomorph of a polar molecule is the nonpolar molecule most
closely resembling it in the size and the structure (e.g., n-butane is the homomorph of
n-butyl alcohol). The nonpolar component of the cohesion energy of a polar solvent is taken
as the experimentally determined total vaporization energy of the corresponding
homomorph at the same reduced temperature (the actual temperature divided by the critical
temperature in Kelvin’s scale). For this comparison the molar volumes must also be equal.
Blanks and Prausnitz proposed plots of dependencies of dispersion energy density on a molar
volume for straight-chain, alicyclic and aromatic hydrocarbons. If the vaporization energies
of appropriate hydrocarbons are not known they can be calculated by one of the
methods of group contributions (See Chapter 5).
Hansen and Scaarup 28 calculated the polar component of solubility parameter using
Bottcher’s relation to estimating the contribution of the permanent dipoles to the cohesion
energy:
where:
δ
2
p
12108 ε−1
=
V 2ε−n
2 2
1
D
( nD
2)
ε dielectric constant,
μ dipole moment
+ μ
[4.1.34]
2 2