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R. Kordala-Markiewicz et al. / Tetrahedron 70 (2014) 4784e4789
3. Conclusion
The solution was stirred at room temperature for 15 min and after
evaporation of the solvent, the product was washed with acetone.
The inorganic salt was separated and acetone was evaporated to
give the product, which was finally dried under reduced pressure at
60 ꢀC for 24 h.
In summary, the obtained results allow us to categorize newly
synthesized 4-chloro-2-methylphenoxyactate ILs as herbicidal
ionic liquids. We demonstrated that the choice of the cation de-
termines the herbicidal effectiveness. In addition, for the first time,
the efficiency of surface tension reduction (pC20) for these HILs was
correlated with the herbicidal activity. In conclusion, the synthe-
sized HILs with longer substituents are very promising herbicidal
agents, with better herbicidal activity in comparison with com-
mercial products.
4.3.2. Alkoxymethylcyclohexyldimethylammonium salts (method
B). Sodium 4-chloro-2-methylphenoxyacetate was synthesized by
reaction of 4-chloro-2-methylphenoxyacetic acid and sodium hy-
droxide. Alkoxymethylcyclohexyldimethylammonium chloride
(0.05 mol) was dissolved in 30 cm3 of deionized water and stoi-
chiometric amount of sodium 4-chloro-2-methylphenoxy-acetate
was added. The solution was stirred at room temperature for 24 h.
Water was evaporated, and anhydrous acetone was added. The
precipitate (NaCl) was filtered and the filtrate concentrated in
a vacuum evaporator. Finally, the product was dried under reduced
pressure at 40 ꢀC for 24 h.
4. Experimental section
4.1. Materials
Cyclohexyldimethylamine, bromoalkanes, potassium, and so-
dium hydroxide as well as all the solvents were purchased from
commercial suppliers (Merck, Aldrich, POCh) and used without
further purification. 4-Chloro-2-methylphenoxyacetic acid was
purchased from Organika-Sarzyna S.A. Poland. Water for surface
activity measurements was deionized with the conductivity below
4.3.3. Cyclohexyldecyldimethylammonium 4-chloro-2-methylphen
oxyacetate (14). dH (DMSO-d6, 298 K, 402.645 MHz): 0.87 (t,
J¼6.5 Hz, 3H, NþeCH2CH2(CH2)7CH3); 1.11 (m, 1H, cyclohexyl C4
axial); 1.26e1.32 (m, 16H, cyclohexyl C3 and C5 axial,
NþeCH2CH2(CH2)7CH3); 1.43 (m, 2H, cyclohexyl C2 and C6 axial);
1.58e1.64 (m, 3H, cyclohexyl C4 equatorial, NþeCH2CH2(CH2)7CH3);
1.85 (m, 2H, cyclohexyl C3 and C5 equatorial); 2.05 (m, 2H, cyclo-
hexyl C2 and C6 equatorial); 2.14 (s, 3H, C]CCH3eC); 2.98 (s, 6H,
Nþe(CH3)2); 3.29e3.34 (m, 2H, NþeCH2CH2(CH2)7CH3); 3.36 (m,
1H, cyclohexyl C1); 4.25 (s, 2H, OeCH2eCOOꢁ); 6.71 (d, J¼6.9 Hz,1H,
COeCH]CH); 7.05 (d, J¼4.2 Hz, 1H, CH]CHeCCl); 7.10 (s, 1H,
CCH3eCH]CCl). dC (DMSO-d6, 298 K, 101.254 MHz): 13.92; 15.90;
21.57; 22.09; 24.81; 25.31; 28.51; 28.70; 28.92; 29.00; 29.05; 29.09;
31.30; 47.62; 61.57; 67.77; 70.45; 112.81; 122.77; 125.89; 127.77;
0.1
m
S cmꢁ1 from demineralizer HLP Smart 1000 (Hydrolab).
Chloromethylalkyl ethers were synthesized by passing HCl through
a mixture of formaldehyde and the appropriate alcohol, and their
purities were above 85%.
4.2. General
1H NMR spectra were recorded on an NMR Varian VNMR-S
spectrometer operating at 400 MHz with TMS as the internal
standard. 13C NMR spectra were obtained with the same in-
strument at 100 MHz. CHN elemental analyses and IR spectra were
performed at the Adam Mickiewicz University, Poznan (Poland).
The water content was determined by using an Aquastar volu-
metric Karl-Fischer titration with Composite 5 solution as the ti-
trant and anhydrous methanol as a solvent.
129.23; 155.89; 170.42. Elemental analysis for
C27H46ClNO3
(M¼468.11) requires (%): C 69.28; H 9.90; N 2.99; found: C 69.59; H
9.68; N 2.63. nmax (KBr): 3600e3100 (br), 2930, 2858, 1616, 1492,
1297, 1233, 1052, 879, 803, 648 cmꢁ1
.
Density was measured with Automatic Density Meter DDM2911
with mechanical oscillator method. Density of the samples (ca.
2.0 cm3), was measured with respect to temperature controlled via
Peltier, from 20 to 60 ꢀC. The apparatus was calibrated using
deionized water and air as reference substances. After each series of
measurements, the densimeter was washed with methanol or ac-
etone and dried. The uncertainty of measurements was estimated
4.3.4. Butoxymethylcyclohexyldimethylammonium 4-chloro-2-
methylphenoxyacetate (19). dH (DMSO-d6, 298 K, 402.645 MHz):
0.89 (t, J¼6.8 Hz, 3H, NþeCH2OCH2(CH2)2CH3); 1.10e1.15 (m, 1H,
cyclohexyl C4 axial); 1.29e1.40 (m, 6H, cyclohexyl C3 and C5 axial,
NþeCH2OCH2(CH2)2CH3); 1.56 (m, 2H, cyclohexyl C2 and C6 axial);
1.67 (d, J¼11.0 Hz, 1H, cyclohexyl C4 equatorial); 1.95 (d, J¼12.0 Hz,
2H, cyclohexyl C3 and C5 equatorial); 2.04 (d, J¼9.8 Hz, 2H, cyclo-
hexyl C2 and C6 equatorial); 2.25 (s, 3H, C]CCH3eC); 3.02 (s, 6H,
Nþe(CH3)2); 3.30 (m, 1H, cyclohexyl C1); 3.70 (t, J¼6.8 Hz, 2H,
NþeCH2OCH2(CH2)2CH3); 4.44 (s, 2H, OeCH2eCOOꢁ); 4.74 (m, 2H,
NþeCH2OCH2(CH2)2CH3); 6.71 (d, J¼8.8 Hz, 1H, COeCH]CH); 7.01
(d, J¼6.4 Hz, 1H, CH]CHeCCl); 7.06 (d, J¼3.4 Hz, 1H, CCH3eCH]
CCl); dC (DMSO-d6, 298 K, 101.254 MHz): 13.67; 16.18; 22.29; 25.12;
25.70; 29.28; 31.24; 44.75; 67.79; 69.27; 72.76; 112.59; 124.30;
125.93; 128.46; 129.87; 130.58; 155.76; 173.46.
to be less than 10ꢁ5 g cmꢁ3
.
Viscosity was determined using a rheometer (Rheotec RC30-
CPS) with cone-shaped geometry (C50-2). The viscosity of the
samples, about 1.5 cm3 was measured with respect to temperature,
from 20 to 100 ꢀC. The uncertainty of the viscosity measurement
was estimated to be less than 10ꢁ4 Pa s.
Refractive index was determined using an Automatic Re-
fractometer J357 with electronic temperature control from 20 to
60 ꢀC. The uncertainty of measurements was estimated to be less
Elemental analysis for C22H36ClNO4 (M¼413.98) requires (%): C
63.83; H 8.77; N 3.38; found: C 63.66; H 8.58; N 3.15. nmax (KBr):
3600e3100 (br), 2936, 2863, 1615, 1491, 1296, 12,323, 1054, 880,
than 10ꢁ5
.
4.3. Preparation
804, 648 cmꢁ1
.
All of the prepared ILs were characterized by 1H NMR and 13C
NMR, and elemental analysisddetails can be found in
Supplementary data.
4.3.1. Alkylcyclohexyldimethylammonium
salts
(method
A). Alkylcyclohexyldimethylammonium bromides (1e9) were syn-
thesized according to methods described earlier.17 Alkylcyclohex-
yldimethylammonium bromide (0.05 mol) was dissolved in
methanol and after addition of a stoichiometric amount of a satu-
rated methanolic solution of KOH, the solution was stirred at room
temperature for 5 min, after which the partially precipitated KBr
was filtered. Then a stoichiometric amount of a saturated meth-
anolic solution of 4-chloro-2-methylphenoxyacetic acid was added.
4.4. Thermal analysis
Thermal transitions of the prepared salts were determined by
DSC, with a Mettler Toledo Stare TGA/DSC1 (Leicester, UK) unit,
under nitrogen. Samples between 5 and 15 mg were placed in
aluminum pans and heated from 25 to 120 ꢀC at a heating rate of