Paper
For the determination of the critical micelle concentrations
RSC Advances
1-Dodecyl-3-(2-hydroxyethyl)-imidazolium chloride (3). N-
(
CMCs) of the surface-active ionic liquids a similar protocol to Dodecylimidazole (5.00 g, 21.2 mmol) was mixed with 2-chlor-
36
ꢀ
our previous work was followed. Solutions at various concen- oethanol (2.90 g, 36.0 mmol). The mixture was heated to 50 C
trations of the ionic liquids were prepared with doubly-distilled for 76 h. Aer evaporation of the remaining volatile materials,
ꢂ1
Millipore Milli-Q water and le under shaking at 360 min for the crude product was twice crystallized from anhydrous THF to
2
4 h at room temperature (RT) to equilibrate. For conductivity yield 1-dodecyl-2-(2-hydroxyethyl)-imidazolium chloride (3) as
1
measurements, samples were previously equilibrated at 25 ꢃ a colourless solid in 74% yield. H NMR (400 MHz, CDCl ; 22
3
ꢀ
ꢀ
0.1 C in a HAAKE K15 thermostat. Conductivity measurements
C): d (ppm) ¼ 9.72 (1H, s, H(2)-im), 7.68 (1H, s, H(5)-im), 7.32
were performed on a Mettler Toledo Seven Excellence system, (1H, s, H(4)-im), 5.13 (1H, m, OH), 4.53 (2H, t, HOCH CH N, J ¼
2
2
equipped with an InLAB 741-ISM electrode (cell constant k ¼ 4.31 Hz), 4.41 (2H, t, NCH , J ¼ 7.21 Hz), 3.83 (2H, t, HOCH -
2
2
0
.105). The conductometer was calibrated with a standard KCl CH N, J ¼ 4.13 Hz), 1.77 (2H, m, NCH CH ), 1.13 (18H, m,
2
2
2
13
solution and two independent measurements were performed. C H CH ), 0.75 (3H, t, NC H CH , J ¼ 7.13 Hz). C NMR (100
9
18
3
11 22
3
ꢀ
The CMC was calculated as the intersection point of the two MHz; CDCl ; 22 C): d (ppm) ¼ 138.10 (d, C(2)-im), 124.12 (d,
3
linear regimes in the conductivity/concentration graph. Surface C(5)-im), 121.72 (d, C(4)-im), 62.69 (t, HOCH CH N), 52.00 (t,
2
2
tension was determined with the Du No u¨ y ring method on HOCH CH N), 50.13 (t, NCH ), 30.11–26.74 (t, C H CH CH ),
2
2
2
8
16
2
3
a Kr u¨ ss manual tensiometer K6 at room temperature. Each 22.48 (t, NCH CH ), 13.93 (q, CH ). The data was in accordance
2
2
3
4
0
measurement was repeated 5 times.
with the literature.
-Dodecyl-3-(2-methoxyethyl)-imidazolium chloride (4). N-
Dodecylimidazole (5.00 g, 21.2 mmol) was mixed with 1-chloro-
1
Synthesis of ionic liquids
2
-methoxyethane (3.60 g, 38.1 mmol). The mixture was heated
and to 80 C for 76 h. Aer evaporation of the remaining volatile
ꢀ
Unfunctionalized imidazolium salts [C12mim]Cl
1
[
C m im]Cl 2 were synthesized according to standard meth- materials, the crude product was twice crystallized from anhy-
12 2
odologies, which include the alkylation of N-methylimidazole or drous THF to yield 1-dodecyl-3-(2-methoxyethyl)-imidazolium
1
dimethylimidazole with the appropriate dodecyl chloride to chloride (4) as a colourless solid in 78% yield. H NMR (400
ꢀ
afford the corresponding imidazolium halide. The imidazolium MHz, CDCl ; 22 C): d (ppm) ¼ 10.67 (1H, s, H(2)-im), 7.49
3
salts were repeatedly crystallized in order to obtain colorless (1H, s, H(5)-im), 7.24 (1H, s, H(4)-im), 4.63 (2H, t, CH OCH -
3
2
solids. All ionic liquids were dried for at least 48 h at room CH N, J ¼ 4.66 Hz), 4.27 (2H, t, NCH , J ¼ 7.45 Hz), 3.75 (2H, t,
2
2
temperature and 0.01 mbar before use and were stored under an CH OCH CH N, J ¼ 4.65 Hz), 3.35 (3H, s, OCH ), 1.88 (2H, m,
3
2
2
3
argon atmosphere.
2 2 9 18 3 11 22 3
NCH CH ), 1.22 (18H, m, C H CH ), 0.84 (3H, t, NC H CH ,
1
3
ꢀ
1
-Dodecyl-3-methylimidazolium chloride (1). Aer following J ¼ 7.21 Hz). C NMR (100 MHz; CDCl ; 22 C): d (ppm) ¼
3
the general procedure the product was repeatedly recrystallized 136.97 (d, C(2)-im), 123.23 (d, C(5)-im), 121.58 (d, C(4)-im),
1
from THF and obtained in 80% yield. H NMR (400 MHz; CDCl
3
;
70.36 (t, CH OC CH N), 58.85 (q, OCH ), 49.49 (t, NCH ),
3 2 2 3 2
ꢀ
2
2 C): d (ppm) ¼ 10.57 (1H, s, H(2)-im), 7.54 (1H, s, H(5)-im), 31.70 (t, CH OCH CH N), 30.22–26.34 (t, C H CH CH ), 22.60
3
2
2
8
16
2
3
7
(
.35 (1H, s, H(4)-im), 4.27 (2H, t, NCH
), 1.86 (2H, m, NCH CH
, J ¼ 6.36 Hz). C NMR (100 H 10.66, N 8.46; found C 65.36, H 11.16, N 8.34.
1-Dodecyl-3-(2-(methylthio)ethyl)-imidazolium chloride (5).
2
, J ¼ 14.83 Hz), 4.09 (t, NCH CH ), 13.91 (q, CH ). ATR-IR (neat): l ¼ 3394, 2922,
2
2
3
ꢂ1
3H, s, NCH
3
2
2
18 35 2
), 1.20 (18H, m, 2853, 1563, 1465, 1166, 1120 cm . C H ClN O: calcd C 65.33,
1
3
C
9
H
18CH
3
), 0.83 (3H, t, NC11
H
22CH
3
ꢀ
MHz; CDCl
3
; 22 C): d (ppm) ¼ 137.35 (d, C(2)-im), 123.76 (d,
C(5)-im), 121.83 (d, C(4)-im), 49.83 (t, NCH ), 36.38 (q, NCH ), Dodecylimidazole (5.00 g, 21.2 mmol) was mixed with (2-
2
3
2
CH
6.09–31.72 (t, C H CH CH ), 22.48 (t, NCH CH ), 13.93 (q, chloroethyl)(methyl)sulfane (2.46 g, 22.2 mmol). The mixture
8 16 2 3 2 2
33
ꢀ
was heated to 80 C for 76 h. Aer evaporation of the remaining
3
). The data was in accordance with the literature.
-Dodecyl-2,3-dimethylimidazolium chloride (2). Aer volatile materials, the crude product was twice crystallized from
1
following the general procedure the product was repeatedly anhydrous THF to yield 1-dodecyl-3-(2-(methylthio)ethyl)-
1
recrystallized from THF and obtained in 92% yield. H NMR imidazolium chloride (5) as a colourless solid in 89% yield.
ꢀ
1
ꢀ
(
2
400 MHz; CDCl
3
; 22 C): d (ppm) ¼ 7.78 (1H, d, H(5)-im, J ¼
H NMR (400 MHz, CDCl ; 22 C): d (ppm) ¼ 10.52 (1H, s, H(2)-
3
.08 Hz), 7.44 (1H, d, H(4)-im, J ¼ 2.04 Hz), 4.10 (2H, t, NCH
2
,
im), 7.80 (1H, s, H(5)-im), 7.37 (1H, s, H(4)-im), 4.56 (2H, t,
J ¼ 14.88 Hz), 3.93 (3H, s, NCH ), 2.70 (3H, s, –CCH ), 1.67 (2H, NCH , J ¼ 6.63 Hz), 4.18 (2H, t, CH SCH CH N, J ¼ 7.58 Hz),
3
3
2
3
2
2
m, NCH CH ), 1.11 (18H, m, CH C H CH ), 0.74 (3H, t, 2.95 (2H, t, CH SCH CH N, J ¼ 4.7.56 Hz), 2.08 (3H, s, SCH ),
2
2
2
9
18
3
3
2
2
3
1
3
ꢀ
NC11
H
22CH
3
, J ¼ 6.86 Hz). C NMR (100 MHz; CDCl
3
2 2 9 18 3
; 22 C): 1.80 (2H, m, NCH CH ), 1.12 (18H, m, C H CH ), 0.75 (3H, t,
1
3
ꢀ
d (ppm) ¼ 143.44 (d, C(2)-im), 123.31 (d, C(5)-im), 121.15 (d, NC H CH , J ¼ 7.09 Hz). C NMR (100 MHz; CDCl ; 22 C):
1
1
22
3
3
C(4)-im), 49.84 (t, NCH
CH ), 22.55 (t, NCH
). The data was in accordance with the literature.
Functionalized imidazolium salts 3–8 were synthesized NCH CH ), 15.51 (q, SCH ), 14.05 (q, CH ). ATR-IR (neat): l ¼
2
), 35.88 (q, NCH
3
), 31.76–26.42 (t, d (ppm) ¼ 138.00 (d, C(2)-im), 123.07 (d, C(5)-im), 121.61 (d,
C
CH
8
H16CH
2
3
2
CH ), 14.00 (q, CH
2
3
), 10.47 (q, C(4)-im), 50.05 (t, CH SCH CH N), 48.59 (t, NCH ), 31.76 (t,
3
2
2
2
33
3
3 2 2 8 16 2 3
CH SCH CH N), 30.44–26.34 (t, C H CH CH ), 22.53 (t,
2
2
3
3
ꢂ1
through a two step procedure involving the alkylation of 1- 3378, 2916, 2847, 1573, 1560, 1467, 1173 cm . C H ClN S:
1
8
35
2
dodecylimidazole which was previously synthesized following calcd C 62.30, H 10.17, N 8.07; found C 62.14, H 10.41, N 8.06.
a procedure reported in the literature and distilled before use
47
with the appropriate halide.
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RSC Adv., 2017, 7, 41144–41151 | 41149