Preparation and chromatographic characteristics of calix[4]arene polysiloxane as stationary phases for capillary gas chromatography

Abstract

Two new kinds of calix[4]arene derivatives, 5, 11, 17, 23-tetra-tert-butyl-25,27-bis(isopropylcarbamoyl-methoxy)-26,28-diundecenyloxy
calix[4]arene (C[4]A) and 25,27-dibutoxy-5, 11, 17, 23-tetra-tert-butyl-26,28-diundecenyloxy calix[4]arene (C[4]B0, are prepared
and then are polymized by two different processes. Three calix[4]arene polysiloxane stationary phases for capillary gas chromatography
are obtained. Their chromatographic characteristics, including column efficiency, polarity, selectivity, glass-transition
temperature and thermal stability are studied. Retention mechanisms are also discussed.

Full text

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Preparation and characteristics of two novel calix[4]arene
polysiloxane stationary phases for capillary gas
chromatography
Zhao-Rui Zeng,* Na Guan, Xing-Hua Tang and Xue-Ran Lu
Department of Chemistry, Wuhan University, 430072 Wuhan, China
Received 7th December 1999, Accepted 3rd March 2000
Published on the Web 10th April 2000
Two novel calix[4]arene derivatives, 5-1A,1A-dimethylundecyloxyphenylmethyl-11,17,23-tris-1B,1B-dimethylethyl-
25,26,27,28-tetrabenzyloxycalix[4]arene polysiloxane (C[4]TB-PSO) and 5-1A,1A-dimethylundecyloxyphenyl-
methyl-11,17,23-tris-1B,1B-dimethylethyl- 25,26,27,28-tetraethoxycarbonylmethyloxycalix[4]arene polysiloxane
(C[4]TECM-PSO), were synthesized and used as stationary phases in capillary gas chromatography. The new
phases demonstrated high column efficiency, a wide operating temperature range, high thermal stability, medium
polarity and excellent selectivity towards alcohol isomers and positional isomers of aromatic compounds. The
selectivity mechanism for positional isomer compounds was investigated by the measurements of thermodynamic
parameters, DH, DS and DG. The inclusion properties of the calix[4]arenes are discussed.
Introduction
Calixarenes are a family of cyclic oligmers prepared from
formaldehyde and para-substituted phenols via cyclic con-
densation under alkaline conditions. It was suggested that the
calixarenes could be regarded as the third host molecule or the
third generation of supramolecules, after crowns and cyclodex-
trins. Considering their unique cavity architecture and high
thermostability, it was expected that the calixarenes and their
derivatives might play an important role in analytical chemistry,
especially in gas chromatography (GC). In fact, Mangia et al.1
reported separation of alcohols, chlorinated hydrocarbons and
aromatic compounds by gas–solid chromatography with p-tert-
butylcalix[8]arene adsorbed on Chromosorb as early as 1983.
Mnuk et al.2,3studied the inclusion properties of p-tert-
butylcalix[n]arene (n = 4–8) in micropacked columns and
fused-silica capillary columns in 1995. However, owing to their
poor solubility in common GC stationary phases, it is difficult to
coat them on the internal wall of the capillary column, thus
resulting in a low column efficiency.
It is well known that polysiloxanes have many advantages,
such as low glass transition temperature, good thermal and
oxidative stability, low surface energy and good film-forming
ability.4Numerous functionalized linear polysiloxanes have
been used as stationary phases in capillary chromatography.5–10
Hence it was of interest to see what will happen when
calixarenes are incorporated into polysiloxanes and used as
stationary phases in capillary chromatography. The poly-
siloxanes should be linear in order to dissolve in organic
solvents. In 1995, Zhong et al.11reported the first efforts in
synthesizing such polymers. The polysiloxanes obtained were
used as stationary phases in capillary chromatography and
demonstrated very high column efficiency. Lim et al.12
prepared calix[4]arene–tetramethyldisiloxane
phases from corresponding dimethyldiallylcalix[4]arene via
hydrosilylation with tetramethyldisiloxane, and then mixed
with OV-1701. In the above-mentioned stationary phases, the
calixarene moieties were incorporated into the main chain of
polysiloxanes and linked through the lower rim of the
calixarene.
The introduction of a long-chain monoalkenyl group at the
upper rim of the calixarene may make it easier to perform
hydrosilylation to synthesize side-chain type calixarene mod-
stationary
ified linear polysiloxanes, and also the pendent calixarene
moieties can move more freely in it to contact substrates. This
kind of calixarene-modified polysiloxane might have special
chromatographic properties and selectivity. In this paper, we
report the synthesis of two novel calixarene-modified poly-
siloxanes in which the calixarene moieties are attached to the
polysiloxane skeleton through their upper rim: 5-1A,1A-dimethyl-
undecyloxyphenylmethyl-11,17,23-tris-1B,1B-dimethylethyl-
25,26,27,28-tetrabenzyloxycalix[4]arene
(C[4]TB-PSO) and 5-1A,1A-dimethylundecyloxyphenylmethyl-
11,17,23-tris-1B,1B-dimethylethyl-25,26,27,28-tetraethoxycar-
bonylmethyloxycalix[4]arene polysiloxane (C[4]TECM-PSO),
and their chromatographic properties when applied in capillary
chromatography. The separation mechanism is also discussed.
The structures of the two calixarenes are given in Fig. 1.
polysiloxane
Experimental
Synthesis of compound 1
5-1A,1A-Dimethylundecenyloxyphenylmethyl-11,17,23-tris-
1B,1B-dimethylethyl-25,26,27,28-tetrahydroxycalix[4]arene (1)
was synthesized as described previously.13
Fig. 1
Structures of the two calixarenes.
This journal is © The Royal Society of Chemistry 2000
DOI: 10.1039/a909625f
Analyst, 2000, 125, 843–848
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Synthesis of C[4]TB
A mixture of compound 1 (0.26 g, 0.30 mmol), toluene (8 ml),
NaOH solution (50%, 0.4 ml), benzyl chloride (0.38 g, 3 mmol)
and tetrabutylammonium bromide (0.01 g, 0.03 mol) was stirred
rapidly at 90–100 °C for 6 h under nitrogen. The cooled mixture
was added to HCl (7 ml) and water (7 ml) and then dried over
anhydrous Na2SO4. After removal of the solvent, the residue
was purified by column chromatography (silica gel) to give 0.29
g (yield 78%). IR (KBr), no IR absorption due to the OH
stretching (3157 cm21) showed that hydroxy groups had been
etherified; 1H NMR (CDCl3, d), 6.18–7.44 (m, 32H, Ar–H),
5.80–3.91 (m, 15H, –CH2NCH2, –CH2Ph, ArCH2Ar), 3.91–3.65
(tri, 2H, O–CH2), 2.98–2.47 [d, 4H, ArCH2Ar), 1.51 (s, 6H,
(CH3)2C] 1.44–0.85 [m, 43H, 3C(CH3)3, –(CH2)8–]; MS
(FAB), m/z 1238 (M+, 11%), 135 (100%); elemental analysis,
found C 84.42, H 9.19; calculated for C88H102O5, C 85.26, H
9.29%.
Synthesis of C[4]TECM
To a solution (5%) of 0.35 g (0.4 mmol) of 1 in dry acetone (8.3
ml), anhydrous K2CO3(0.11 g) and bromoethyl acetate (0.66 g,
4 mmol) were added. The mixture was refluxed under nitrogen.
After the reaction was completed (monitored by TLC), the
cooled mixture was filtered. The residue was washed with
CH2Cl2 several times and the combined organic layer was
concentrated to an oily liquid. After removal of bromoethyl
acetate in vacuum, the purification of crude product by column
chromatography (silica gel) gave 0.369 g (yield 81%) of solid.
IR (KBr), the disappearance of IR absorption (OH stretching,
3157 cm21) and the appearance of IR absorption (CNO
stretching, 1760 cm21) suggested that the hydroxy group had
been etherified; 1H NMR (CDCl3, d), 6.26–7.11 (m, 12H, Ar–
H), 5.28–3.91 (m, 23H, –CHNCH2, O–CH2–CNO, ArCH2Ar,
–O–CH2CH3), 3.91–3.61 (tri, 2H, O–CH2), 3.09–2.96 (m, 4H,
ArCH2Ar), 1.48 [s, 6H, (CH3)2C], 1.48–0.82 [m, 43H,
3C(CH3)3, –(CH2)8–]; MS (FAB), m/z 1224 (M+, 219%), 287
(100%); elemental analysis, found C 75.21, H 83; calculated for
C76H102O13, C 74.60, H 8.40%.
Synthesis of C[4]TB-PSO
A 0.12 g amount of C[4]TB and 0.11 g of polymethylhy-
drosiloxane were mixed in 5 ml of pure benzene and heated at
90 °C for 1 h in a three-necked flask under an argon atmosphere.
A 10 ml volume of chloroplatinic acid solution (1%
HPtCl6·6H2O, 1% ethanol and 98% tetrahydrofuran) as catalyst
was added to the mixture, which was stirred at 90 °C for 6 h,
after which time it became a viscous solution. IR analysis
showed that the Si–H bond still existed, so decylene (1 ml) was
then added and the mixture was stirred for an additional 1 h to
substitute completely the residual Si–H groups with 1-octyl
groups (monitored from spectra). After 1 h the mixture was
allowed to cool. The gummy product was taken out and
dissolved in 10 ml of methylene chloride, then washed seven
times with 30 ml of methanol–water (1 + 1) to remove the
catalyst. The solvent was vaporized and the gummy product was
dried under reduced pressure. IR (KBr), the disappearance of IR
absorption (2160 cm21) indicated that the Si–H groups had
been completely substituted.
Synthesis of C[4]TECM-PSO
The synthesis method for C[4]TECM-PSO is similar to that for
C[4]TB-PSO, except that 0.14 g of C[4]TECM and 0.126 g of
polymethylhydrosiloxane were used.
Column preparation
Fused silica columns (0.25 mm id, Yong Nian Optical Fibre
Factory, Hebei Province, China) were rinsed with 10 column
volumes of methanol and then flushed with nitrogen at
250–300 °C for 2 h. The capillaries were statically coated with
a solution of 0.5% (w/v) C[4]TB-PSO or C[4]TECM-PSO in
dichloromethane. After flushing with nitrogen at room tem-
perature for 2 h, the columns were conditioned at 320 °C for 10
h under a slow flow of nitrogen before use.
Column evaluation
The apparatus used for column evaluation was an SC-7 gas
chromatograph (Sichuan Analytical Apparatus Plant, Sichuan,
China) equipped with a split injection system and flame
ionization detector. The carrier gas was nitrogen at a linear
velocity of 12–15 cm s21and a splitting ratio of 80+1 was used
for all columns. The injector temperature was maintained at
330 °C and the detector temperature was held at 300 °C. The
selectivity and average polarity of those columns were charac-
terized by the McReynolds constants. The efficiency of these
columns was evaluated by measuring the number of plates m21
for naphthalene at 120 °C. The glass transition temperature was
determined by the change in slope of the log k versus1/Tplot for
naphthalene. The thermostability of these stationary phases was
tested by measuring the column bleed and by differential
scanning calorimetry (DSC) on a DT-40 instrument (Shimadzu,
Kyoto, Japan).
Results and discussion
C[4]TB-PSO and C[4]TECM-PSO both have polysiloxane
segments. The phenolic hydroxy groups in the lower rims of the
two calixarene derivatives are modified by benzyl and ester
groups, which make them exhibit different properties in some
respects. Therefore, they are predicted to have good film-
forming ability, high thermal stability, high efficiency and
unique selectivity.
Fig. 2
C[4]TB-PSO column. Conditions: 21 m 3 0.25 mm id; temperature,
programmed from 180 to 310 °C. Peaks: 1 = dimethyl phthalate; 2 =
diethyl phthalate; 3 = dibutyl phthalate; 4 = diamyl phthalate; 5 =
diisohexyl phthalate; 6 = dihexyl phthalate; 7 = diisooctyl phthalate; 8 =
dioctyl phthalate; 9 = dinonyl phthalate; 10 = didecyl phthalate.
Chromatogram of long-chain phthalate diesters (C1–C10) on the
844
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The chromatographic properties of the studied columns are
summarized in Table 1. The column efficiencies are 4225 and
3498 plates m21for C[4]TB-PSO and C[4]TECM-PSO,
respectively. The peak asymmetry factors for octanol on the
fused-silica columns are close to 1.0, which shows that all the
columns have good inertness on the inner wall and a good film-
forming ability. C[4]TB-PSO showed much better reproduci-
bility.
The operational temperature range was determined by the
glass transition temperature and column bleeding temperature.
The glass transition temperature was obtained from the plot of
log k of naphthalene versus the reciprocal of absolute tem-
perature for the two calix[4]arene columns. The changes in
slope at 115 °C for C[4]TB-PSO and 130 °C for C[4]TECM-
PSO correspond to the changes. These results also correspond to
the glass transition temperature determined by DSC of these
two polymers. However, these changes in the slopes of the two
curves appeared virtually identical. This implies that the
thermodynamic properties of the two columns are very similar
in the two states at the transition point of the glass transition
temperature. The thermostability was determined by the column
bleeding, which was measured by programming the temperature
from 200 to 320 °C at 4 °C min21. The columns began to bleed
at 280 °C for C[4]TB-PSO and 270 °C for C[4]TECM-PSO, and
the shift of the baseline was 4 3 10214A for C[4]TB-PSO and
2 310213A for C[4]TECM-PSO at 320 °C. DSC confirmed the
results. The decomposition temperatures were 450 °C for
C[4]TB-PSO and 420 °C for C[4]TECM-PSO. The baseline
shift for C[4]TECM-PSO was greater than that for C[4]TB-
PSO. These results suggest that the calixarene containing
benzyl groups has higher thermostability than the calixarene
containing ester groups, which shows that C[4]TB-PSO is more
suitable for separating samples at high temperatures. Phthalic
diesters are environmental pollutants and have high boiling-
points. Fig. 2 shows that the long-chain phthalate diesters (C1–
C10) are well separated on C[4]TB-PSO by programming the
operating temperature from 180 to 310 °C at 6 °C min21.
Therefore, both columns have wider operating temperature
ranges. The allowable temperature range of C[4]TB-PSO is
wider than that of C[4]TECM-PSO.
The selectivity and polarity of the two columns, represented
by McReynolds constants,14which were measured at 120 °C,
are given in Table 2. The mean McReynolds constants are 141
for C[4]TB-PSO and 151 for C[4]TECM-PSO. The results
indicate that the two columns exhibit moderate polarity, similar
to that of OV-1701. Owing to the ester substituent, C[4]TECM-
PSO has a stronger polarity than C[4]TB-PSO. The values of XA,
YA and UA for C[4]TB-PSO are greater than those for C[4]TB-
PSO. This indicates that C[4]TECM-PSO possesses a better
selectivity than C[4]TB-PSO for aromatic hydrocarbons, alco-
hols and nitrogen-containing compounds.
Fig. 3 shows chromatograms for the Grob test mixture
obtained on the two columns. They show that the mixtures were
well separated and each peak is symmetrical. It is notable that
naphthalene eluted at the end of the chromatogram, which is
different from the results with OV-1701.15This can be
explained by the strong p–p interaction between the solute and
calixarenes, which implies a special retention behavior of
calixarenes toward aromatics.
The calix[4]arene polysiloxane phases possess excellent
selectivity for the separation of aromatic and alcohols. Table 3
gives separation factors (a) and capacity factors (k) for the
compounds investigated. The C[4]TB-PSO phase shows ex-
cellent separation of nitrotoluenes and nitroethylbenzenes. It is
interesting that the elution of the solutes on the C[4]TB-PSO
column was not only dependent on the dipole–dipole reaction,
Table 1
Characteristic properties of C[4]TB-PSO and C[4]TECM-PSO capillary columns
Stationary phase
Column
dimensions/
m 3 mm id
Column
efficiency/
plates m21
(naphthalene)
Capacity
factor (k)
Peak
asymmetry
factor
(octan-1-ol)
Film thickness/
mm
Baseline shift
at 320 °C/A
C[4]TB-PSO 1
C[4]TB-PSO 2
C[4]TECM-PSO
12 3 0.25
21 3 0.25
14.4 3 0.25
4225
4136
3498
4.80
4.70
3.57
1.02
1.03
1.02
0.31
0.31
0.31
4 3 10214
6 3 10214
2 3 10213
Table 2
McReynold’s constants of the studied stationary phases
Stationary phaseBenzene XA
Butanol YA
Pentan-2-one zA
Nitropropane UA
Pyridine SA
SumMeana
C[4]TECM-PSO
C[4]TB-PSO
OV-1701
94
88
67
156
134
170
135
111
153
202
173
228
170
199
171
757
705
789
151
141
158
aMean = sum/5.
Fig. 3
column, 14.4 m 3 0.25 mm id, temperature 110 °C, and (b) C[4]TB-PSO
column, 12 m 3 0.25 mm id, temperature 120 °C. Peaks: 1 = decane; 2 =
butane-1,3-diol; 3 = undecane; 4 = octan-1-ol; 5 = dodecane; 6 =
2,6-dimethylphenol; 7 = 2,4-dimethylaniline; 8 = naphthalene; unlabelled
peak = solvent.
Chromatogram of Grob text mixture on (a) C[4]TECM-PSO
Analyst, 2000, 125, 843–848
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Page 4

but also on the steric hindrance. The sequence of dipole–dipole
force is 2,5-DNT < 2,4-DNT < 2,3-DNT < 2,6-DNT <
3,5-DNT < 3,4-DNT (DNT = dinitrotoluene), but the retention
times decrease in the order 2,6-DNT < 2,5-DNT < 2,3-DNT <
2,4-DNT < 3,5-DNT < 3,4-DNT. The elution sequence is
similar to that of dihydroxy-substituted saturated urushiol
crown ether phase.16This difference is possibly caused by the
steric hindrance of the 2,6-DNT and 2,3-DNT molecules, which
do not fit into the cavity of calix[4]arene, so the interaction
between them is diminished. For nitrochlorobenzene and
nitrotoluene isomers, the dipole–dipole strength decreases in
the order o- > m- > p-, but the elution sequence on C[4]TB-
PSO is m-, p-, o-, because para-isomers fit better in the cavities
of C[4]TB-PSO. From Fig. 4 it can be seen that butanediol
positional isomers are well separated on both calix[4]arene
phases. Furthermore, the calix[4]arene derivatives also exhibit
excellent selectivity for phenolic compounds.
In order to study the retention and separation mechanism of
these columns, thermodynamic parameters of six groups of
positional isomers, namely dichlorobenzene, nitrotoluene, ni-
troethylbenzene, dinitrobenzenes, dinitrotoluene and chloro-
phenols, on the C[4]TB-PSO and C[4]TECM-PSO columns
were measured. The enthalpy of solution (DH), the entropy of
solution (DS), the free energy of solution (DG) and DH/DS, are
listed in Table 4.
Table 4 shows that the magnitude of the DG values agrees
with the retention order of the isomers. The greater the 2DG
value, the longer is the retention time. Both DH and DS
contribute to the elution order of positional isomers. However,
from the values of DS/DH, it can be predicted whether DH or
DS determines the solute elution order. The smaller the values
of DS/DH, the longer are the retention times of the solutes on
the columns. Hence it can be concluded that on both columns
the separations are controlled by DH.
The DS values of all the positional isomers on C[4]TECM-
PSO are greater than those on C[4]TB-PSO, which shows that
the steric hindrance on C[4]TECM-PSO is greater. On the other
hand, the DH values of almost all the compounds on
C[4]TECM-PSO are greater than those on C[4]TB-PSO. This
indicates that C[4]TECM-PSO, substituted by the ester groups,
provides greater polarity than C[4]TB-PSO, which is substi-
tuted by phenyl groups.
The contributions of hydrogen bonding interactions to
separations on the two stationary phases differ greatly. On
C[4]TECM-PSO, the ester groups can form hydrogen bonds
with solute molecules. The hydrogen bonding interaction
contributes considerably to its selectivity. As can be seen on
comparing o-, m- and p-chlorophenol, the DH value of o-
chlorophenol is much smaller, because the intramolecular
hydrogen bonds obviously weaken its hydrogen bonding
interaction with C[4]TECM-PSO. In contrast, hydrogen bond-
ing interaction does not play such an important role on C[4]TB-
Table 3
Capacity factors (k) and separation factors (a) for positional isomers on the two columns
C[4]TECM-PSOC[4]TB-PSO
Compound
k
a
k
a
Temperature/
°C
o-Dimethylbenzene
m-Dimethylbenzene
p-Dimethylbenzene
2.246
1.831
1.795
1.25
1.02
1.00
1.837
1.514
2.147
1.21
1.00
1.42
80
o-Dichlorobenzene
m-Dichlorobenzene
p-Dichlorobenzene
3.277
2.611
2.729
1.26
1.00
1.05
3.079
2.431
2.557
1.27
1.00
1.05
100
Butane-1,4-diol
Butane-1,3-diol
Butane-2,3-diol
1.925
1.035
0.532
3.62
1.95
1.00
1.718
0.969
0.532
3.23
1.82
1.00
110
o-Nitrotoluene
m-Nitrotoluene
p-Nitrotoluene
3.833
3.331
3.628
1.15
1.00
1.09
3.968
3.619
3.333
1.19
1.09
1.00
140
o-Dinitrobenzene
m-Dinitrobenzene
p-Dinitrobenzene
3.916
4.298
4.788
1.00
1.10
1.22
3.073
3.342
4.045
1.00
1.09
1.32
170
2,6-Dinitrotoluene
2,5-Dinitrotoluene
2,3-Dinitrotoluene
2,4-Dinitrotoluene
3,5-Dinitrotoluene
2,4-Dinitrotoluene
4.205
5.313
6.062
6.286
6.999
8.534
1.00
1.26
1.44
1.50
1.66
2.03
3.986
5.017
6.339
5.847
6.795
8.796
1.00
1.26
1.59
1.47
1.71
2.21
170
o-Chlorophenol
m-Chlorophenol
p-Chlorophenol
3.060
3.345
3.810
1.00
1.09
1.25
0.297
1.573
1.065
1.00
4.40
2.98
180
Fig. 4
m 3 0.25 mm id, and (b) C[4]TB-PSO column, 12 m 3 0.25 mm id,
temperature 110 °C. Peaks: 1 = butane-1,2-diol; 2 = butane-1,3-diol; 3 =
butane-1,4-diol.
Chromatogram of butanediol on (a) C[4]TECM-PSO column, 14.4
846
Analyst, 2000, 125, 843–848

Page 5

PSO, because phenyl groups cannot provide the ability to form
hydrogen bonds with solutes. The differences in DH values of
o-, m- and p-chlorophenol on C[4]TB-PSO are small. The above
conclusion can also be confirmed by the YA values in the
McReynolds constants.
Calixarene, possessing a cup-shaped structure, is capable of
selective interaction with many organic molecules.2,3Figs. 5
and 6 show the plot of log k for three groups of homologous
series (alcohols, alkylbenzenes and halo derivatives) on the two
calixarene columns against the boiling-point.
It is obvious that benzene and toluene molecules are all
included on both columns. The steric arrangement of benzene
and toluene molecules is relatively more suitable for the cavity
of the calixarene than is that of other aromatic homologous
molecules, which strengthen the interaction with the calixar-
enes, including CH3(host)–p (guest) and CH3(guest)–p (host)
interactions.
The log k of ethanol deviates from linearity on both columns
because the ethanol molecules are encapsulated in the two kinds
of calix[4]arene cavity. Methanol only can form inclusion
complexes with C[4]TECM-PSO. This may because the cavity
size of C[4]TECM-PSO is more suitable for methanol mole-
cules and C[4]TECM-PSO has higher polarity than C[4]TB-
PSO.
The retentions for trichloromethane on both columns are
retarded. The molecules of trichloromethane have a stronger
electrostatic force than the other homologues with these
calixarene phases, which increases the probability of inclusion
in the calix[4]arene cavity.
Conclusion
The two new calixarene phases were modified by introducing
different functional groups on the lower rims, and then
polymerized. These two columns possess good thermal stabil-
ity, wide temperature ranges and unique selectivity for alcohols,
aromatic compounds and positional isomers. Solution thermo-
dynamic parameters show that the functional groups on the
Table 4
DS)
Values of DH/kJ mol21, DS/J mol21K21, DG/kJ mol21and (DS/DH)/1023K21on C[4]TB-PSO and C[4]TECM-PSO (DG = DH 2 0.373
C[4]TB-PSO (A)C[4]TECM-PSO (B)
CompoundIsomer
2DH
2DS
2DG
DS/DH
2DH
2DS
2DG
DS/DH
Elution
sequence
Nitrochlorobenzene
o-
m-
p-
49.20
47.58
48.04
107.47
104.71
105.26
9.11
8.52
8.78
2.18
2.20
2.19
78.04
77.25
76.51
178.10
176.86
175.76
11.61
11.28
10.95
2.28
2.29
2.30
(A) m, p, o
(B) p, m, o
Nitrotoluene
o-
m-
p-
49.52
47.86
47.97
108.13
105.33
104.89
9.19
8.57
8.85
2.18
2.20
2.19
79.54
78.48
77.72
181.48
179.67
178.48
11.85
11.46
11.15
2.28
2.29
2.30
(A) m, p, o
(B) p, m, o
Nitroethylbenzene
o-
m-
p-
46.79
48.34
49.06
104.32
105.10
105.45
7.88
9.14
9.73
2.23
2.26
2.15
71.78
73.61
74.48
165.45
167.12
167.84
10.07
11.27
11.88
2.30
2.27
2.25
(A) m, p, o
(B) o, m, p
Dinitrobenzene
o-
m-
p-
56.06
56.88
58.05
113.89
114.90
116.42
13.58
14.02
14.63
2.03
2.04
2.22
54.96
55.02
56.26
113.89
113.36
114.52
12.48
12.74
13.54
2.07
2.06
2.04
(A) o, m, p
(B) o, m, p
Chlorophenol
o-
m-
p-
49.43
47.74
52.07
121.46
108.37
116.34
4.13
7.32
8.68
2.46
2.27
2.23
50.20
74.07
68.40
120.57
159.30
149.91
5.16
14.65
12.48
2.41
2.15
2.19
(A) o, m, p
(B) o, p, m
Dinitrotoluene (DNT) 2,6-59.83
60.79
60.92
65.70
66.69
64.12
122.32
122.49
121.59
132.20
133.57
126.61
14.20
15.10
15.57
16.39
16.87
16.90
2.04
2.01
2.00
2.01
2.00
1.97
73.01
76.16
78.28
75.65
80.69
81.69
153.46
158.72
161.60
156.17
166.54
166.59
15.77
16.96
18.00
17.40
18.57
19.55
2.10
2.08
2.06
2.06
2.06
2.04
(A) 2,6, 2,5,
2,3, 2,4,
3,5 3,4
(B) 2,6, 2,5,
2,4, 2,3,
3,5, 3,4
2,5-
2,3-
2,4-
3,5-
3,4-
Fig. 5
point. (-) Alkan-1-ols (methanol, ethanol, propan-1-ol, butan-1-ol and
pentan-1-ol); (5) aromatics (benzene, toluene, ethylbenzene, propylben-
zene and butylbenzene); (:) chloromethanes (dichloromethane, trichloro-
methane and tetrachloromethane).
Relationship between logkof (C[4]TECM-PSO) phase and boiling-
Fig. 6
point. Symbols as in Fig. 5.
Relationship between logk of (C[4]TB-PSO) phase and boiling-
Analyst, 2000, 125, 843–848
847