Physical Chemistry Chemical Physics
Page 14 of 15
The interaction of the investigated molecules with the 1-
octanol molecules is stronger than with those of 1-hexane
as the first one has hydrogen bonding centers), which
diagrammatic method. The influence of the crystal lattice
(
contributions on the solubility values of the investigated
DOI: 10.1039/C6CP00379F
entails a decrease in the entropy (system ordering).
However, the enthalpy term prevails over the entropy one,
which is reflected in the negative values of the transfer
Gibbs energy. It should be noted that the transfer processes
compounds in the selected solvent was demonstrated.
The contributions of the Gibbs energy of sublimation
and hydration to the process of dissolution in the buffer (in
percentage terms) were compared. For compound II the
sublimation term is only 4%, whereas the hydration one –
96%. In turn, for compound III, the sublimation term
reaches 55%, whereas the hydration one – 45%. In other
words, when designing an unsubstituted molecule for
compound II, the main contribution to the solubility
increase is practically made through improvement of the
hydration characteristics of the molecule. On the other
hand, for compound III, the sublimation term exceeds the
hydration one, which leads to lowering the solubility values.
It was compared the contributions of the Gibbs energy
of sublimation and solvation to the process of dissolution in
1-octanol. For compound VI the sublimation term is 19%,
whereas the solvation one – 81%. On the other hand, for
compound VII the sublimation term is 79%, whereas the
solvation one – 21%. Thus, we can conclude that if the
for compounds III and
V in (1-hexane → 1-octanol) system
occur without an entropy change, only by the enthalpy
factor (i.e. by enhancing the interactions of the substance
with the molecules of 1-octanol as compared to 1-hexane.
In turn, compound
I has approximately the same
interaction with the solvent molecules in different phases,
but the entropy of transition changes significantly (toward
disorder) for all the systems. The transfer of the molecules
from 1-hexane to 1-octanol describes specific interactions
of the solute with 1-octanol because 1-hexane is a solvent
interacting with dissolved molecules only through non-
specific (van-der-Waals) interactions. The ratio of the
specific interactions (donor-acceptor ones, hydrogen
bonds) to the non-specific ones is a very important
characteristic of the substance in a certain solvent, which
determines
all
transport
properties
(diffusion,
structural modification of reference molecule
dissolution processes for compounds III IV VII and VIII are
controlled by the crystal lattice. Whereas for compounds II
and VI, the dissolution processes are controlled by the
solvation phenomena.
I occurs, the
permeability). In other words, it is this feature that is the
clue to understanding membrane permeability processes.
It should be emphasized that the process of the
transition from aqueous to octanol phase slightly differs
from the distribution process between these phases. First
of all this is determined by the existence of the mutual
solubility of 1-octanol in water (the octanol content in
water is 0.5 M/L) and water in 1-octanol (containing about
,
,
,
V
The contributions of the Gibbs energy of sublimation
and solvation to the process of dissolution in 1-hexane
were assessed. For compound
V the sublimation term is
93%, whereas the solvation one – 7%. On the other hand,
for compound II the sublimation term is 14%, whereas the
solvation one is 86%.
2
.3 M/L of H O in octanol). The experimental distribution
2
coefficients and those derived from the transfer procedure
differ not essentially for compounds which are poor soluble
The relationships between the solubility Gibbs energies
in the selected solvents and melting points were obtained.
The correlation equation between the solubility Gibbs
19
in water (The investigated substances belong just to that
class of compounds). At that, for the highly soluble in water
compounds the considered deviations can be essential and
require carefully usage of the obtained parameters.
energies in 1-hexane and molecular polarizability (α) was
received. The transfer processes from buffer to 1-octanol,
from buffer to 1-hexane and 1-hexane to 1-octanol were
analyzed.
Conclusions
Eight adamantane derivatives of sulfonamides were
synthesized and characterized. Temperature dependences
of saturation vapor pressure were obtained by the
transpiration method and thermodynamic functions of the
sublimation processes were calculated. Thermophysical
characteristics of fusion processes (melting points and
fusion enthalpies) of the substances were measured by the
DSC method. The solubility values of the selected
compounds in buffer (pH 7.4), 1-octanol and 1-hexane were
determined at different temperatures by the isothermal
saturation method. The thermodynamic functions of
solubility and solvation/hydration processes were studied.
To determine the effect of the substituents introduced in
the unsubstituted molecule on the thermodynamic
characteristics of dissolution and solvation / hydration, we
analysed the differences of these thermodynamic functions
for substituted and unsubstituted compounds using the
Acknowledgements
This work was supported by the Russian Science Foundation
(No.14-13-00640).
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