122
M. A. Czarnecki and S. Morita
asynchronous contour plots made possible to identify the peaks from the terminal
CH 2 next to OH and the peaks from the midchain CH 2 .
A lot of efforts were undertaken for examination of microheterogenity in binary
mixtures [24–27]. 2DCOS-NIR studies on propyl alcohols/water mixtures reveal
the separation at a molecular level and the presence of homoclusters of water and
alcohol existing in equilibrium with the mixed clusters (heteroclusters) [24]. The
presence of these clusters is responsible for macroscopic structure of the mixtures
and leads to anomalous physicochemical properties. In the water-poor region, the
molecules of alcohols are in the same environment as those in the pure liquid alcohols, while the molecules of water are dispersed in the organic phase. When the
water content increases, the molecules of water form clusters interacting with the
OH groups of the alcohols. These results clearly show that the degree of microheterogeneity in alcohol/water mixtures is closely related to the extent of self-association
of the alcohol.
Interestingly, similar conclusion was obtained from 2DCOS-NIR and chemometric studies of binary mixtures of methanol with short-chain aliphatic alcohols
[25]. The degree of deviation from the ideal mixture is correlated with the chain length
and the order of the alcohol. For most of the mixtures, the largest deviation from the
ideality appears at equimolar mixture. The heteroclusters were observed in the whole
range of mole fractions, while the homoclusters occur above a certain concentration
limit. It is interestingly to note that the homoclusters of both components are similar
as those observed in neat liquids.
In spite of similar structure and properties of methanol and its deuterated derivative, CH 3 OH/CD 3 OH mixture also deviates from the ideal mixture [26]. The extent
of this deviation is much smaller as compared with the mixtures of unlike alcohols
[25], and it results mainly from the difference between the CH 3 and CD 3 groups. It is
of note that the contribution to heterogeneity from the OH groups is relatively small.
The CH 3 OH/CD 3 OH mixture is composed of the homoclusters of both alcohols and
the mixed clusters. The homoclusters in the mixture are similar to those present in
neat alcohols. The highest population of the heteroclusters and the largest deviation
from the ideal mixture appears at equimolar mixture.
2DCOS-NIR and chemometric study on microheterogeneity in binary mixtures
of aliphatic and aromatic hydrocarbons has shown that even relatively weak interactions like π-π or differences in molecular shapes may give rise to deviation from
the ideality [27]. The extent of these deviations is small for aromatic/aromatic
or aliphatic/aliphatic mixtures and increases for aromatic/aliphatic mixtures. The
shape of molecules has a significant effect on the extent of deviation from the ideal
mixture. If both components of the mixture have similar shapes (linear or cyclic), the
molecules with the same probability form the homo- and heteroclusters, otherwise,
increases the tendency for formation of the homoclusters. Since the homoclusters
of both components resemble those in neat liquids, one can conclude that deviation
from the ideal mixture is due to presence of the heteroclusters. Interesting information provides 2D correlation moving-window spectrum. Figure 6.9 displays the
composition-dependent moving-window spectrum of n-hexane/benzene mixture. It
is of note that the spectral changes from the aromatic and aliphatic parts are clearly
M. A. Czarnecki and S. Morita
asynchronous contour plots made possible to identify the peaks from the terminal
CH 2 next to OH and the peaks from the midchain CH 2 .
A lot of efforts were undertaken for examination of microheterogenity in binary
mixtures [24–27]. 2DCOS-NIR studies on propyl alcohols/water mixtures reveal
the separation at a molecular level and the presence of homoclusters of water and
alcohol existing in equilibrium with the mixed clusters (heteroclusters) [24]. The
presence of these clusters is responsible for macroscopic structure of the mixtures
and leads to anomalous physicochemical properties. In the water-poor region, the
molecules of alcohols are in the same environment as those in the pure liquid alcohols, while the molecules of water are dispersed in the organic phase. When the
water content increases, the molecules of water form clusters interacting with the
OH groups of the alcohols. These results clearly show that the degree of microheterogeneity in alcohol/water mixtures is closely related to the extent of self-association
of the alcohol.
Interestingly, similar conclusion was obtained from 2DCOS-NIR and chemometric studies of binary mixtures of methanol with short-chain aliphatic alcohols
[25]. The degree of deviation from the ideal mixture is correlated with the chain length
and the order of the alcohol. For most of the mixtures, the largest deviation from the
ideality appears at equimolar mixture. The heteroclusters were observed in the whole
range of mole fractions, while the homoclusters occur above a certain concentration
limit. It is interestingly to note that the homoclusters of both components are similar
as those observed in neat liquids.
In spite of similar structure and properties of methanol and its deuterated derivative, CH 3 OH/CD 3 OH mixture also deviates from the ideal mixture [26]. The extent
of this deviation is much smaller as compared with the mixtures of unlike alcohols
[25], and it results mainly from the difference between the CH 3 and CD 3 groups. It is
of note that the contribution to heterogeneity from the OH groups is relatively small.
The CH 3 OH/CD 3 OH mixture is composed of the homoclusters of both alcohols and
the mixed clusters. The homoclusters in the mixture are similar to those present in
neat alcohols. The highest population of the heteroclusters and the largest deviation
from the ideal mixture appears at equimolar mixture.
2DCOS-NIR and chemometric study on microheterogeneity in binary mixtures
of aliphatic and aromatic hydrocarbons has shown that even relatively weak interactions like π-π or differences in molecular shapes may give rise to deviation from
the ideality [27]. The extent of these deviations is small for aromatic/aromatic
or aliphatic/aliphatic mixtures and increases for aromatic/aliphatic mixtures. The
shape of molecules has a significant effect on the extent of deviation from the ideal
mixture. If both components of the mixture have similar shapes (linear or cyclic), the
molecules with the same probability form the homo- and heteroclusters, otherwise,
increases the tendency for formation of the homoclusters. Since the homoclusters
of both components resemble those in neat liquids, one can conclude that deviation
from the ideal mixture is due to presence of the heteroclusters. Interesting information provides 2D correlation moving-window spectrum. Figure 6.9 displays the
composition-dependent moving-window spectrum of n-hexane/benzene mixture. It
is of note that the spectral changes from the aromatic and aliphatic parts are clearly