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3.1.2. Preparation of phenyl 2,5-dichlorobenzenesulfonate
(1a)
ꢀ15 cm3 working volume). The cell is first loaded with a
measured amount of sulfonate to within ꢄ0.002 g. To remove
entrapped air the cell is degassed with CO2 very slowly at
pressures less than 3 bar and then CO2 is transferred into the
cell gravimetrically to within ꢄ0.02 g using a high-pressure
bomb. The mixture in the cell is viewed with a borescope
(Olympus Corporation, model F100-024-000-55) placed
against a sapphire window secured at one end of the cell. A
stir bar is activated by a magnet located below the cell to mix
the contents of the cell. The solution temperature is measured to
within ꢄ0.1 8C (type K thermocouple calibrated against a
NIST certified thermometer) and is held constant to within
ꢄ0.3 8C. The system pressure is measured with a Heise
pressure gauge accurate to within ꢄ20 psi for data to
10,000 psig and with a pressure transducer (Viatran model
245) to within ꢄ50 psi for data higher than 10,000 psig. The
constant-composition mixture in the cell is compressed to a
single phase and the pressure is then slowly decreased until a
second phase appears. A dew point is obtained if a fine mist
appears in the cell and a solidification point is obtained if solid
particles appear in the cell. The pressure–temperature data
points of any given isopleth are averaged values from phase
transition measurements reproduced two-to-three times to
within ꢄ30 psi. Once an isopleth is obtained, more CO2 is
added to the cell to dilute the solution, and measurements are
repeated at this new concentration. The solution concentrations
of a given isopleth have an accumulated error of ꢀ1.0%.
Solution density data are also determined in the single-phase
region just prior to the phase transition using a linear
displacement technique [19,20] given in detail elsewhere
[21]. At a given pressure and temperature the volume of the cell
is determined by detecting the location of the internal piston
with an LVDT coil (Lucas Schaevitz Co., model 2000-HR) that
fits around a 1.43 cm high-pressure tube and tracks the
magnetic tip of a steel rod connected to the piston. Solution
densities are calculated knowing the amount of material in the
cell and the cell volume. The solution densities have an
accumulated uncertainty of ꢄ1.5% [21].
A flask was charged with 2,5-dichlorobenzenesulfonyl
chloride (10.0 g, 40.7 mmol), phenol (4.0 g, 44.8 mmol),
dichloromethane (100 mL), and then in one portion triethyla-
mine (5.9 mL) was added and the mixture was allowed to react
with stirring at ambient temperature for 2 h. The mixture was
diluted with ether (300 mL) and washed with water
(2 ꢃ 150 mL), and then brine (ꢀ50 mL). The organic layer
was separated and dried over magnesium sulfate, filtered, and
the solvents removed under reduced pressure. The crude
product was recrystallized from hexanes to afford 1a as
colorless crystals (10.8 g, 87%, mp 85–87 8C). 1H NMR
(200 MHz CDCl3): d 7.85 (dd, J = 2.0, 0.9 Hz, 1H), 7.47
(overlapping d, 2H), 7.30–7.20 (m, 3H), 7.11–7.04 (m, 2H); 13
C
NMR (50 MHz CDCl3): d 144.1, 129.8, 129.75, 128.2, 128.0,
126.9, 126.4, 124.8 (C30 & C50), 122.4, 116.7 (C20 & C60).
Anal. Calcd for C12H8Cl2O3S: C, 47.53; H, 2.64. Found: C,
47.79; H, 2.63.
3.1.3. Preparation of pentafluorophenyl 2,5-
dichlorobenzenesulfonate (1b)
A flask was charged with pentafluorophenol (8.24 g,
44.8 mmol), dichloromethane (100 mL), 2,5-dichlorobezene-
sulfonyl chloride (10.0 g, 40.8 mmol), and then in one portion
triethyl amine (5.9 mL) was added and the mixture was allowed
to react with stirring at ambient temperature for 2 h. The
mixture was diluted with ether (300 mL) and washed with
water (2 ꢃ 150 mL), and then brine (ꢀ50 mL). The organic
layer was separated and dried over magnesium sulfate, filtered,
and the solvents removed under reduced pressure. The crude
product was recrystallized from hexanes (ꢀ250 mL) to afford
1
1b as colorless crystals (11.0 g, 70%, mp 120–122 8C). H
NMR (200 MHz CDCl3): d 7.92 (dd, J = 2.0, 0.9 Hz, 1H), 7.56
(d, J = 2.0 Hz, 1H), 7.55 (d, J = 0.9 Hz, 1H). Anal. Calcd for
C12H3Cl2F5O3S: C, 36.67; H, 0.77; F, 24.17. Found: C, 36.77;
H, 0.76; F, 24.26.
3.1.4. Preparation of 2,2,3,3,4,4,5,5-octafluoropentyl 2,5-
dichlorobenzenesulfonate (1c)
3.1.6. Single-crystal molecular structure determinations
for phenyl 2,5-dichlorobenzenesulfonate (PDBS) and
A flask was charged with octafluoropentanol (10.4 g,
44.8 mmol), dichloromethane (100 mL), 2,5-dichlorobezene-
sulfonyl chloride (10.0 g, 40.8 mmol), and then in one portion
triethyl amine (5.9 mL) was added and the mixture was allowed
to react with stirring at ambient temperature for 2 h. Work up as
detailed above and then Kugelrhor distillation (0.2 mm, 150–
160 8C) afforded 1c as a light amber oil (11.0 g, 70%). 1H NMR
(200 MHz CDCl3): d 8.02 (dd, J = 2.0 Hz, 1H), 7.55 (d,
J = 2.0 Hz, 1H), 7.49 (s, 1H), 5.95 (tt, J = 5, 51 Hz, 1H), 4.57 (t,
J = 13 Hz, 2H). Anal. Calcd for C11H6Cl2F8O3S: C, 29.94; H,
1.36; F, 34.47. Found: C, 30.21; H, 1.38; F, 34.28.
pentafluorophenyl 2,5-dichlorobenzenesulfonate (FPDBS)
Single-crystals of PDBS were grown from cooling a hot
hexanes solution and FPDBS from a hot methanol solution.
Crystals were selected and mounted on glass fibers and epoxied
in place for data collection on a Siemens R3 4-circle
diffractometer using graphite monochromated Mo Ka radia-
tion. Data collection in u–2u mode yielded 2206 unique
reflections with Rint = 0.026 for PDBS and 2428 unique
reflections with Rint = 0.023 for FPDBS. The structures were
solved using SHELXTL-PC software [22] by direct methods.
Hydrogen atoms were included in the final refinements and
refined in the riding mode. Least squares refinement PDBS
using 1725 reflections (Fo > 4s), 163 parameters, resulted in
R1 = 0.0393, GOF = 1.06 and for FPDBS, 1747 (Fo > 4s)
reflections gave R1 = 0.0695 and a GOF = 1.67. The details of
the data collection and refinement are summarized in Table 1.
3.1.5. Phase behavior measurements
Described elsewhere are the apparatus and techniques used
to obtain sulfonate-CO2 phase behavior data [5,18]. The main
component of the experimental apparatus is a high-pressure,
variable-volume cell (Nitronic 50, 7.0 cm o.d. ꢃ 1.5 cm i.d.,