48
Y. Wang et al. / Journal of Molecular Catalysis A: Chemical 379 (2013) 46–52
Table 1
The solubility of PEG-DILs and PEG-DAILs at room temperature.a
Entry
IL
H2O
EtOH
Et2O
Acetone
Benzene
AcOEt
PhNO2
PhMe
1
2
3
4
5
6
7
PEG200-DIL
PEG400-DIL
PEG1000-DIL
PEG2000-DIL
PEG4000-DIL
PEG200-DAIL
PEG1000-DAIL
s
s
s
s
s
s
s
s
s
s
s
s
s
s
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
s
s
s
s
s
s
s
i
i
i
i
i
i
i
a
s, soluble; i, insoluble.
PEG200-DIL: 1H NMR (500 MHz, CDCl3, ppm) ı 2.68 (s, 6H,
2 × SO3CH3), 3.58–3.61 (m, 11H, (OCH2CH2)n), 3.84 (4H, 2 × CH2),
4.0 (s, 6H, 2 × NCH3), 4.46 (s, 4H, 2 × CH2), 7.64 (s, 2H, 2 × CH), 7.67
(s, 2H, 2 × CH), 9.36 (s, 2H, 2 × CH); 13C NMR (126 MHz, CDCl3,
ppm) ı 36.2, 39.6, 49.4, 68.8, 70.1, 70.3, 123.2, 123.5, 137.4; IR
(KBr, cm−1): 3460, 3107, 2874, 1842, 1514, 1408, 1371, 1352, 1144,
808, 721, 642; ESI-MS: 184.22 (M++/2, n = 4), 206.12 (M++/2, n = 5),
228.31 (M++/2, n = 6), 250.11 (M++/2, n = 7), 272.23 (M++/2, n = 8),
83.14 (100).
2.5. General procedure for acetalization in PEG1000-DAIL/toluene
system
Aromatic aldehydes (2 mmol) and alcohols (3 mmol) were
added into a 10 mL tube reactor preloaded with PEG1000-DAIL
(2 mL) and toluene (2 mL). The reacution mixtre was stirred at 80 ◦C
for 1 h. After the reaction, the mixture was cooled to room temper-
ature and the mixture separated into two phases. After decantation
of the upper phase, the below phase was reused for the next time
after removing water under vacuum at 80 ◦C for 1 h.
PEG400-DIL: 1H NMR (500 MHz, CDCl3, ppm) ı 2.68 (s, 6H,
2 × SO3CH3), 3.47–3.49 (m, 33H, (OCH2CH2)n), 3.73 (4H, 2 × CH2),
3.89 (s, 6H, 2 × NCH3), 4.36 (s, 4H, 2 × CH2), 7.48 (s, 2H, 2 × CH), 7.57
(s, 2H, 2 × CH), 9.46 (s, 2H, 2 × CH); 13C NMR (126 MHz, CDCl3, ppm)
ı 36.2, 39.5, 49.5, 69.1, 70.2, 70.3, 122.8, 123.6, 138.1; IR (KBr, cm−1):
3447, 3106, 2883, 1853, 1576, 1458, 1377, 1350, 1192, 858, 721,
640; ESI-MS: 294.12 (M++/2, n = 9), 316.42 (M++/2, n = 10), 338.13
(M++/2, n = 11), 360.33 (M++/2, n = 12), 382.13 (M++/2, n = 13), 108.9
(95).
2.6. General procedure for acetalization in
PEG1000-DIL/toluene/PTSA system
Aromatic aldehydes (2 mmol), ethylene glycol (3 mmol) and
para-toluenesulfonic acid (3 mmol) were added into a 10 mL tube
reactor preloaded with PEG1000-DIL (2 mL) and toluene (2 mL). The
reaction mixture was stirred at 80 ◦C for 4 h, the mixture was then
cooled to room temperature to let phase separation. After decanta-
tion of the upper phase, the below phase was reused for the next
run after removing water under vacuum at 80 ◦C for 1 h.
PEG1000-DIL: 1H NMR (500 MHz, CDCl3, ppm) ı 2.78 (s, 6H,
2 × SO3CH3), 3.61–3.77 (m, 87H, (OCH2CH2)n), 3.77 (m, 4H,
2 × CH2), 4.01 (s, 6H, 2 × NCH3), 4.52 (t, J = 4.5 Hz, 4H, 2 × CH2), 7.30
(s, 4H, 4 × CH), 7.67 (s, 2H, 2 × CH); 13C NMR (126 MHz, CDCl3, ppm)
ı 36.1, 39.6, 49.3, 68.8, 70.2, 70.3, 123.3, 137.5, 137.6; IR (KBr, cm−1):
3445, 3107, 2874, 1840, 1531, 1456, 1410, 1319, 1107, 849, 771,
625; ESI-MS: 448.17 (M++/2, n = 16), 470.20 (M++/2, n = 17), 492.20
(M++/2, n = 18), 514.27 (M++/2, n = 19), 558.27 (M++/2, n = 21), 580.30
(M++/2, n = 22), 602.33 (M++/2, n = 23), 624.36 (M++/2, n = 24), 646.36
(M++/2, n = 25), 668.37 (M++/2, n = 26), 690.43 (M++/2, n = 27), 712.43
(M++/2, n = 28), 153.07 (100).
3. Results and discussion
3.1. The solubility of PEG-DILs and PEG-DAILs in organic solvents
were tested at different temperatures. It was found that PEG-DILs
such as ethanol and nitrobenzene, but insoluble in less polar sol-
vents such as diethyl ether, acetone, benzene, ethyl acetate and
toluene at room temperature (Table 1). Among them, PEG1000-DIL
temperature-dependent biphasic system with toluene. The phase
diagrams of PEG1000-D(A)IL/toluene systems were shown in Fig. 1.
The thermoregulated process of PEG1000-DAIL/toluene system
was demonstrated in Fig. 2. It was obvious from Fig. 2 that the phase
separation was totally complete. The volume and color of toluene
phase (upper layer) was unchanged. Actually, the quantitative test
of the solubility of PEG1000-DAIL in toluene was done and found
that the solubility was no more than 0.2 wt% at 0 ◦C and 0.6 wt%
at 20 ◦C, in average of ten dissolution–separation cycles. In com-
parison, that of PEG1000-DIL was no more than 0.3 wt% at 0 ◦C and
0.9 wt% at 20 ◦C, furthermore, much longer time was required to
ensure complete phase separation. Another most important point
was that the mixture could form a homogeneous solution at 80 ◦C
since it was complete transparent and no micelle could be observed.
PEG2000-DIL: 1H NMR (500 MHz, CDCl3, ppm) ı 2.73 (s, 6H,
2 × SO3CH3), 3.44–3.71 (m, 177H, (OCH2CH2)n), 3.72–3.81(m, 4H,
2 × CH2), 3.96 (d, J = 7.0 Hz, 6H, 2 × NCH3), 4.45 (s, 4H, 2 × CH2), 6.99
(s, 4H, 4 × CH), 7.61 (s, 2H, 2 × CH); 13C NMR (126 MHz, CDCl3, ppm)
ı 36.6, 39.9, 49.8, 70.6, 70.7, 70.8, 123.4, 123.8, 138.4; IR (KBr, cm−1):
3441, 3149, 2883, 1846, 1523, 1466, 1398, 1319, 1113, 843, 719,
627.
PEG4000-DIL: 1H NMR (500 MHz, CDCl3, ppm) ı 3.06 (s, 6H,
2 × SO3CH3), 3.29–3.74 (m, 362H, (OCH2CH2)n), 3.88 (s, 6H,
2 × NCH3), 4.35 (s, 4H, 2 × CH2), 7.29 (s, 4H, 4 × CH), 8.56 (s, 2H,
2 × CH); 13C NMR (126 MHz, CDCl3, ppm) ı 37.4, 39.7, 49.7, 61.4,
67.7, 69.9, 70.7, 122.3, 124.0, 136.9; IR (KBr, cm−1): 3460, 3144,
2883, 1842, 1537, 1468, 1402, 1319, 1147, 843, 689, 627.
2.4. General procedure for esterification in PEG1000-DAIL/toluene
system
Aromatic acids (2 mmol) and alcohols (3 mmol) were added
into a 10 mL tube reactor preloaded with PEG1000-DAIL (2 mL) and
toluene (2 mL). The reaction mixture was stirred thoroughly at 80 ◦C
for 1 h. After the completion of reaction, the mixture separated into
two phases at room temperature, the upper phase was decanted for
analysis and the below phase was reused for the next time directly
or after removing water under vacuum at 80 ◦C for 1 h.
3.2. Esterification of aromatic acids in PEG1000-DAIL/toluene
catalyst–medium system
Esterification is one of the most traditional and basic reaction in
synthetic chemistry and chemical engineering. It is also extensively