FULL PAPERS
Niklaas J. Buurma et al.
chloride was from Sigma, cesium hydroxide hydrate was from
Acros and 4-n-propylbenzenesulfonyl chloride was from
Lancaster and all were used as received. Sodium 4-methyl-
benzenesulfonate and sodium 4-ethylbenzenesulfonate were
prepared by neutralizing the corresponding acid using a
sodium hydroxide solution, followed by filtration and evapo-
ration of the solvent. Cesium 4-methylbenzenesulfonate was
prepared analogously using CsOH hydrate. All prepared salts
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1
were tested and found pure using H NMR and elemental
analysis. All hydrotropes were stored in a desiccator over P O
2
5
or KOH. NMR spectra were recorded on Varian Gemini 200
1
1
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(
H: 200 MHz) and VRX 300 ( H: 300 MHz) spectrometers,
7
with HOD set to 4.79 ppm. In the determination of the
1
[18] H. Benak, J. B. F. N. Engberts, M. J. Blandamer, J. Chem.
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concentration dependence of the H NMR spectra of 2b, 2d
and 2e, methanol was added as a second reference. The signal
of methanol did not shift with respect to the set signal of HOD.
Elementalanalyseswere performed byH. Draayer andJ. Ebels
of the analytical section of this department.
[
21] S. E. Friberg, L. Fei, S. Campbell, H. F. Yang, Y. C. Lu,
Colloids Surf. A 1997, 127, 233 ± 239.
Sodium 4-n-Propylbenzenesulfonate (2d)
[
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4
-n-Propylbenzenesulfonyl chloride, 15 g (65 mmol) was sus-
pended in 1 M aqueous NaOH and stirred vigorously for 2 days
at 40 8C. The resulting acidic solution was neutralized and the
solvent evaporated, resulting in a 1:1 sodium 4-n-propylben-
zenesulfonate/NaCl mixture; yield: 18.2 g (65 mmol). The
mixture was extracted continuously overnight in a Soxhlet
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propylbenzenesulfonate was extracted to avoid contamination
[
[
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5
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with NaCl. The absence of sodium chloride was confirmed
1
using a silver nitrate precipitation test. H NMR (D O): d
2
0
.88 (3H, CH CH CH , t), 1.61 (2H, CH CH CH , sextet), 2.64
2 2 3 3 2 2
(
2H, CH CH CH , t), 7.36 and 7.71 (4H, phenyl, AB-system);
3 2 2
anal. calcd. for C H SO Na: C 48.64, H 4.99, S 14.43%; found:
9
11
3
[28] V. Srinivas, D. Balasubramanian, Langmuir 1995, 11,
C 48.30, H 4.84, S 14.30%.
2
830 ± 2833.
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849.
[
[
[
[
[
1
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À1
1
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[
[
[
[
[
[
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2
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420
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