The Journal of Organic Chemistry
N,N-Diethyl-N-methylammonium terminated PIB oli-
Page 6 of 7
(5) (10 g, 8.2 mmol) was dissolved in 100 mL of heptane.
Then, acetone (100 mL) and 10 equiv. of sodium tetrafluorobꢀ
orate were added into the reaction mixture. The reaction was
stirred for 24 h. The solvents were removed under removed
pressure using a rotary evaporator. Then, hexane was added
into the crude product, where the hexane solution was extractꢀ
ed with water (3 x 50 mL). The hexane layer was dried with
Na2SO4 and the solvent was removed under reduced pressure
using a rotary evaporator to afford 8.73 g of 8 (94 % yield). 1H
NMR (300 MHz, CDCl3) δ: 0.68ꢀ1.82 (m, 276 H), 2.92ꢀ3.29
(m, 5 H), 3.29ꢀ3.60 (m, 4 H).
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gomer with benzoate anion (6) and phenol-phenolate anion
(7). In general, the ionꢀexchange reaction was done by using
an ionꢀexchange column made up of Amberlite IRA400 (hyꢀ
droxide form) resin beads. The ionꢀexchange resin was first
treated with a solution of sodium hydroxide to ensure that the
ammonium functional groups on the resins were present as
ammonium hydroxide salts. After the eluent was tested to be
basic by using a pH paper, the resins were then rinsed with
water until the eluent has a pH of 7 to remove any excess
aqueous NaOH. A solution of benzoic acid or phenol in methꢀ
anol was then added into the ionꢀexchange column until the
eluent has the same pH as the starting solution. Again, the
resins were rinsed with either methanol, acetonitrile, or hepꢀ
tane until the eluent has a neutral pH. Lastly, a solution of 0.6
g of 5 in heptane was passed through the column to generate
either N,N-diethylꢀN-methylammonium terminated PIB oliꢀ
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Tetra-n-butylammonium benzoate (TBA-benzoate).
The same procedure as mentioned in the synthesis of 6 was
used with the exception that acetonitrile was used instead of
heptane because of the insolubility of tetraꢀnꢀbutylammonium
salts in heptane. In this chemistry, 0.18 g (0.5 mmol) of tetraꢀ
nꢀbutylammonium iodide in 10 mL of acetonitrile was conꢀ
verted into 0.14 g of the TBAꢀbenzoate (78% yield). This
compound was also prepared using a 1 M solution of tetraꢀn-
butylammonium hydroxide in MeOH and equivalent amount
of benzoic acid. The reaction was stirred for 24 h in the presꢀ
ence of magnesium sulfate. The reaction mixture was filtered
and the solvent of removed under reduced pressure using a
rotary evaporator. Then the white solids were dried under vacꢀ
uum for another 24 h. 6 prepared from TBAꢀOH or by ion
exchange was equally effective and spectroscopically identiꢀ
cal. 1H NMR (400 MHz, CDCl3) δ: 0.91 (m, 12 H), 1.37 (m, 8
H), 1.47 (m, 8 H), 3.40 (dd, 1 H), 3.2 (m, 8 H), 7.21 (m, 3 H)
8.00 (m, 2 H); 13C NMR (125 MHz, CDCl3) δ: 13.4, 19.4,
23.7, 58.32, 127.1, 128.7, 129.3.
gomer with benzoate anion
6
or N,N-diethylꢀN-
methylammonium terminated PIB oligomer with phenoxide
anion 7. The majority of the heptane solvent was removed
under reduced pressure using a rotary evaporator to yield 1.2 g
of 6 as a viscous oil. The conversion of 5 to 6 was measured
by 1H NMR spectroscopy using the integral of the aryl protons
of the benzoate relative to the methyl protons of carbons adjaꢀ
cent to the cationic nitrogen of the ammonium salt. The conꢀ
version was quantitative (100 %). The larger than expected
mass for the isolated oil and the larger than expected signal for
the aliphatic protons in the ca. 0.8ꢀ2.0 δ region for 6 was asꢀ
cribed to the presence of some residual heptane in the viscous
oil product. While excess hexane or heptane in other syntheꢀ
ses of functionalized PIB oligomers can be removed on heatꢀ
ing under reduced pressure, prior studies with PIB oligomers
containing ammonium salts has indicated that heating can
produce side reactions (e.g. Hofmann eliminations) so the
viscous oil product was directly used. The ammonium salt 7
was similarly formed with 100% conversion of the end group.
The 1.1 g of the viscous oil product 7 that was isolated in the
same scale reaction was also a larger than expected mass. As
discussed above, this larger mass and the larger than expected
signal for the aliphatic protons in the ca. 0.8ꢀ2.0 δ region for 7
was ascribed to the presence of some residual heptane in the
viscous oil product 7. The resins used in synthesis of 6 and 7
were also reusable by retreatment of the spent resin with soluꢀ
tions of aqueous NaOH and benzoic acid or phenol to recycle
the resins used in the ionꢀexchange reaction. N,N-DiethylꢀN-
methylammonium terminated PIB oligomer with benzoate
anion 6: 1H NMR (300 MHz, CDCl3) δ: 0.86ꢀ1.92 (m, 420 H),
3.18 (dd, 1 H), 3.28 (dd, 1 H), 3.33 (s, 3 H) 3.68 (m, 4 H), 7.33
(m, 3 H), 8.11 (m, 2 H). 13C NMR (75 MHz, CDCl3) δ: 8.3,
multiple peaks between 23.5 and 38.3, 48.6, 53.0, multiple
peaks between 57.6 and 59.7, 69.0, 127.9, 129.8, 130.7, 136.7,
171.5. N,N-DiethylꢀN-methylammonium terminated PIB oliꢀ
gomer with phenolate anion 7: 1H NMR (300 MHz, CDCl3) δ:
0.93ꢀ1.45 (m, 364 H), 2.88ꢀ2.92 (m, 5 H), 3.23 (m, 4 H), 6.56
(m, 1 H), 6.80 (m, 2 H), 7.07 (m, 2 H). 13C NMR (75 MHz,
CDCl3) δ: 8.0, 23.2, 24.7, multiple peaks between 29.0 and
38.1, 48.2, 53.0, 56.6, multiple peaks between 57.6 and 59.5,
68.5, 115.8, 117.4, 129.3, 135.6, 162.7.
Tetra-n-butylammonium phenol-phenolate (TBA-
phenol-phenolate). This compound can be prepared by a
reported procedure.16 1H NMR (400 MHz, CDCl3) δ: 0.92 (m,
12 H), 1.29 (m, 8 H), 1.36 (m, 8 H), 2.97 (dd, 1 H), 3.2 (m, 8
H), 6.58 (m, 2 H), 6.86 (m, 4 H), 7.06 (m, 4 H); 13C NMR
(125 MHz, CDCl3) δ: 13.6, 19.5, 23.8, 58.3, 115.8, 117.1,
129.2, 162.1
Typical procedure for kinetic studies of SN2 reactions.
For the kinetic studies, a 0.1 M solution of equivalent amounts
of the substrates, the nucleophile source, and cyclooctane was
prepared in MeOH, MeCN, DMF, or heptane. The reaction
was either stirred at 35 °C or 55 °C. An aliquot (100 ꢁL) of the
reaction mixture was taken at different time intervals. In cases
where polar solvents were used, the aliquot was diluted with 1
mL of diethyl ether and washed with 1 mL of water. The two
phases with separated and the organic layer was dried with
anhydrous sodium sulfate. The solution was then submitted for
GC analysis. In the case of heptane, an aliquot (100 ꢁL) of the
reaction mixture was passed through a pipette silica gel colꢀ
umn using 1 mL of hexanes. The eluent was submitted in the
GC for analysis. The rate constant, k, was calculated by using
Solver in Excel for nonꢀlinear curve fitting.
Typical procedure for solid/liquid phase catalysis and
catalyst recycling. The reaction was carried out using a 0.1 M
solution of 1ꢀbromobutane and 10 mol% of 8 in heptane (10
mL). Potassium acetate (3 eq) was added into the reaction
mixture and the reaction was stirred for 24 h at 90 °C. After 24
h, the solution was decanted from the solid and MeCN (2 x 10
mL) was added to remove the low molecular weight species
from the heptane solution of the PIBꢀbound ammonium salt.
N,N-Diethyl-N-methylammonium terminated PIB oli-
gomer with boron tetrafluoride anion (8). N,N-DiethylꢀN-
methylammonium terminated PIB oligomer with iodide anion
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