J. Chem. Sci. (2018) 130:48
Page 3 of 13 48
of 2,2-bis ((3-methylimidazolidin-1-yl) methyl) propane-1,3- was dispersed in dry methanol (15 mL). The [HFDAIL] ionic
diol bromide salt (IL-Br): A mixture of 1-methylimidazole liquid (0.25 g) was dissolved in hot methanol (10 mL) and
(6.25 mmol, 0.5 mL) and 0.65 g of 2,2-bis (bromomethyl)- addedslowlyintothepreparedmixture. Afterthat, themixture
1,3-propanediol (2.5 mmol) was heated at 150 ◦C for 8 h was stirred at room temperature for 24 h. Upon completion
under magnetic stirring. After cooling to room temperature, of the process, the solvent (methanol) was evaporated under
the obtained solid was washed three times with acetonitrile reduced pressure. Finally, the resulting solid was washed with
◦
and the residue was dried in an oven at 100 C for 2 h, ◦giv- acetone (2 ×10 mL) and dried under vacuum at 70 ◦C for 5 h
ing IL-Br as a white powder (yield: 95.25 %, M.p.: 150 C). togivenanosilica-supportedhydroxyl-functionalizeddiacidic
1H NMR (DMSO-d6): δ 3.24 (4H, s, CH2N), 3.84 (6H, s, ionic liquid (nanosilica@[HFDAIL]) as a white powder.
CH3), 4.31 (4H, s, CH2OH), 4.72 (2H, s, OH), 7.42 (4H,
dd, J = 10 Hz, J = 5 Hz, CH = CH) and 8.72 (2H, s,
2.2c Immobilization of [SFDAIL] onto the silica nano-
NCHN) ppm; 13C NMR (DMSO-d6): δ 35.94, 45.21, 48.58,
particles: Silica nanoparticles were dried in an oven at
250 ◦C for 6 h. In a round bottom flask, 1.5 g of nanosil-
ica was dispersed in dry methanol (15 mL). The [SFDAIL]
ionic liquid (0.5 g) was dissolved in hot methanol (10 mL) and
addedslowlyintothepreparedmixture. Afterthat, themixture
was stirred at room temperature for 24 h. Upon completion
of the process, the solvent (methanol) was evaporated under
reduced pressure. Finally, the resulting solid was washed with
acetone (2 ×10 mL) and dried under vacuum at 70 ◦C for 5 h
to give nanosilica supported sulfonated diacidic ionic liquid
(nanosilica@[SFDAIL]) as a white powder.
ν
58.48, 123.72, 123.86 and 137.38 ppm; FT-IR (KBr)
:
max
621, 771, 830, 1061, 1165, 1451, 1573, 1760, 1656, 2935 and
3261 cm−1
.
2.2.1bPreparationof3,3’-(2,2-bis((sulfoxy)methyl)propane-
1,3-diyl) bis (1-methyl-1H-imidazole-3-ium) bromide
[SFDAIL]: The sulfonic acid-functionalized ionic liquid, was
prepared by nucleophilic substitution reaction of IL-Br salt
with chlorosulphonic acid. To do this, 0.8 g of IL-Br salt
(2 mmol) was dissolved in acetonitrile. Then 0.5 mL of
chlorosulphonic acid (8 mmol) was added slowly at room
temperature. Then, the mixture was stirred for 4 h at the same
temperature. The reaction mixture was filtered to give yellow
precipitate. It was washed with toluene three times and dried
under vacuum at 100 ◦C for 1 h, giving SFDAIL as a yellow
2.3 Typical procedure for the esterification reaction
with nanosilica@[HFDAIL]
1
The typical procedure for esterification of phthalic anhy-
dride with butanol as an example, was performed as follows:
phthalic anhydride (1 mmol, 0.15 g), butanol (5 mmol, 0.46
mL, 0.37 g) and nanosilica@[HFDAIL] as catalyst (10 mol%
to phthalic anhydride, 0.05 g) were poured into a 50 mL round
bottom flask equipped with a dean-stark apparatus, reflux con-
denser and a magnetic stirrer. Then the mixture was stirred
at 125 ◦C for 8 h. The completion of reaction was monitored
by TLC using (EtOAC/Hexane 2:8) as eluent. After comple-
tion of the reaction as indicated by TLC, ethyl acetate was
added to dissolve the product and then the reaction mixture
was filtered to separate the catalyst from the reaction mixture.
Then, ethyl acetate was evaporated under vacuum to afford
the desired product as yellow oil liquid at 92% yield (0.25
g, B.p.: 340 ◦C). The obtained product (dibutyl phthalate)
solid (yield: 97.5%). H NMR (DMSO-d6): δ 3.33 (4H, s,
CH2N), 3.47 (6H, s, CH3), 4.04 (4H, s, CH2OH), 5.33 (2H,
s, SO3H), 7.06 (4H, d, J = 5 Hz, CH = CH) and 8.30 (2H, s,
NCHN) ppm; 13C NMR (DMSO-d6): δ 36.19, 43.83, 48.27,
ν
63.89, 123.88, 124.26 and 137.79 ppm; FT-IR (KBr)
:
max
587, 783, 1019, 1252, 1459, 1585, 1709 and 3160 cm−1
.
2.2.1.cPreparationof3,3’-(2,2-bis(hydroxymethyl)propane-
1,3-diyl) bis (1-methyl-1H-imidazole-3-ium) hydrogen sulfate
[HFDAIL]: The hydroxyl functionalized ionic liquid was pre-
pared by anion exchange of IL-Br salt. 0.5 g (1.2 mmol)
of IL-Br salt, obtained in the first stage, was dissolved in
methanol (30 mL) under stirring. After that, the system was
◦
slowly heated up to 60 C in an oil bath. Then, 0.13 mL of
sulfuric acid (2.4 mmol) was added drop-wise and stirred for
24 h. Upon completion of the reaction, the solvent was evapo-
rated under vacuum. The resultant material was washed with
dichloromethane (3 × 5 mL) and then dried under vacuum at
100 ◦C for 2 h to afford HFDAIL as yellow viscous oil liquid
◦
was subjected to drying under vacuum at 70 C for 5 h. The
solid catalyst was washed with acetone to remove the residual
product and dried under vacuum at 70 ◦C.
1
in 95% yield. H NMR (DMSO-d6): δ 3.20 (4H, s, CH2N),
3.81 (6H, s, CH3), 4.27 (4H, s, CH2OH), 4.74 (2H, s, OH),
7.39 (4H, dd, J = 10 Hz, J = 5 Hz, CH = CH) and 8.69
(2H, s, NCHN) ppm; 13C NMR (DMSO-d6): δ 36.73, 44.97,
49.63, 59.53, 124.31, 124.58 and 138.73 ppm; FT-IR (KBr)
3. Results and Discussion
3.1 Catalyst characterization
νmax
: 590, 776, 880, 1054, 1223, 1458, 1572, 1642, 2510,
For the preparation of supported acidic ILs, [HFDAIL]
and [SFDAIL] were initially synthesized using read-
ily available or pre-synthesized precursors. Then, the
prepared acidic ILs were immobilized onto the nanosil-
ica via hydrogen bonding of either sulfonic acid or
3096 and 3329 cm−1
.
2.2b Immobilization of [HFDAIL] onto the silica
nanoparticles: Silica nanoparticles were dried in an oven
at 250 ◦C for 6 h. In a round bottom flask, 0.75 g of nanosilica hydroxyl group in ILs with surface hydroxyl group of