Mixture
s formed by a pyridine ba
se and alkane, benzene, or 1-alkanol have been inve
stigated in the frameworkof the Kirkwood-Buff theory. In thi
s work, the derivative
s of the molar exce
ss Gibb
s energie
s (
GE), relativeto the mole fraction, needed for the determination of the Kirkwood-Buff integral
s (
Gij) and related quantitie
swere calculated u
sing the DISQUAC group contribution model. Sy
stem
s with alkane
s are characterized byinteraction
s between
similar molecule
s (
G12 < 0). Mixture
s with pyridine or 4-methylpyridine
show
Gii curve
swith a maximum at high amine concentration
s, which indicate
s that amine-amine interaction
s are
strongerthan in
solution
s with dimethyl or trimethylpyridine
s. For
solution
s with a given alkane, the increa
se of methylgroup
s in the aromatic ring of the pyridine lead
s to a decrea
se of
G11 in the following
sequence
s: pyridine> 4-methylpyridine and pyridine > 2-methylpyridine > 2,4-dimethylpyridine > 2,4,6-trimethylpyridine. The
same variation
s are ob
served for the molar exce
ss enthalpie
s (
HE), and volume
s (
VE). Sy
stem
s with benzeneor 1-alkanol
s show lower
![](/image<font color=)
s/entitie
s/verbar.gif">
G12![](/image<font color=)
s/entitie
s/verbar.gif"> value
s than tho
se with alkane
s. Thi
s ha
s been a
scribed to the exi
stence ofinteraction
s between di
ssimilar molecule
s, which are of dipolar type. The compari
son of
G12 for 1-alkanol +pyridine ba
se (or + benzene or + toluene) mixture
s clearly reveal
s that the interaction
s between di
ssimilarmolecule
s are much more predominant in amine
sy
stem
s. However, their local mole fraction
s are
scarcelydependent on the intermolecular interaction
s and the di
stribution of the molecule
s in the
solution i
s practicallyrandom, even in methanol
sy
stem
s.