ChCl
mim]Cl
Choline chloride
1-Butyl-3-methylimidazolium chloride
Dimethylformamide
Dimethyl sulfoxide
N,N¢-Dimethyl urea
Half maximal effective concentration
Environment, health, safety
1-Ethyl-3-methylimidazolium chloride
Ethyl acetate
Giftklasse (Swiss poison class)
1-Hexyl-3-methylimidazolium tetrafluorobo-
rate
High performance liquid chromatography
Ionic liquid
Median lethal concentration
Median lethal dose
12 X. Qi, M. Watanabe, T. M. Aida and R. L. Smith Jr., Ind. Eng. Chem.
Res., 2008, 47, 9234–9239.
[C
4
1
3 S. Hu, Z. Zhang, Y. Zhou, B. Han, H. Fan, W. Li, J. Song and Y. Xie,
Green Chem., 2008, 10, 1280–1283.
DMF
DMSO
DMU
EC50
EHS
14 H. Zhao, J. E. Holladay, H. Brown and Z. C. Zhang, Science, 2007,
316, 1597.
1
5 G. Yong, Y. Zhang and J. Y. Ying, Angew. Chem., Int. Ed., 2008, 47,
9
345–9348.
1
6 Aside from solution systems, solid methods like ball milling have
been introduced, however showing drawbacks because thermal and
substrate flux are limited in such systems: G. W. V. Cave, C. L. Raston
and J. L. Scott, Chem. Commun., 2001, (21), 2159.
7 G. Imperato, E. Eibler, J. Niedermeier and B. K o¨ nig, Chem.
Commun., 2005, 11701; G. Imperato, S. H o¨ ger, D. Lenoir and B.
K o¨ nig, Green Chem., 2006, 8, 1051; G. Imperato, R. Vasold and B.
K o¨ nig, Adv. Synth. Catal., 2006, 348, 2243–2247; G. Imperato, B.
K o¨ nig and C. Chiappe, Eur. J. Org. Chem., 2007, 1049; D. Reinhardt,
F. Ilgen, D. Kralisch, B. K o¨ nig and G. Kreisel, Green Chem., 2008,
10, 1170–1182; F. Ilgen and B. K o¨ nig, Green Chem., 2009, 11, 848–
854.
[
C mim]Cl
2
EtOAc
GK
1
[C
6
mim][BF ]
4
HPLC
IL
LC50
LD50
Log KOW
Me
NMR
PE
pTsOH
1
1
8 [C
4
mim]Cl: Aldrich >98.0% purity, 25 g, 385 €; [C
4 6
mim][PF ]:
Log octanol-water partitioning coefficient
Methyl-
Nuclear magnetic resonance
Petrol ether
Para-toluene sulfonic acid
Scandium (III) triflate
Acros >97,5% purity, 25 g, 117 €; [C
purity, 50 g, 329 €; Choline chloride: Sigma >98,0% purity, 0.5 kg,
35 € .
9 ChCl is used as food additive and the tolerable upper intake level
for adults was determined to be 4900 mg daily; S. C. Sweetman,
6
mim][BF ]: Aldrich >97,0%
4
(
ed) Martindale: the complete drug reference, Pharmaceutical Press,
Sc(OTf)
3
London, 33rd edn., 2002.
T
dec
Decomposition temperature
Thermogravimetric analysis
N,N¢-Tetramethyl urea
Wassergef a¨ hrdungsklasse (German water haz-
ard class)
20 ChCl is readily biodegradable according to OECD-criteria (93%
biodegradation within 14 days) in a MITI I-Test (MITI, 1992). For
the bioaccumulation, a bioconcentration factor (BCF) of 0.59 was
found indicating that no bioaccumulation is to be expected. OECD
SIDS Initial Assessment Report for SIAM 19, 2004.
TGA
TMU
WGK
2
2
2
1 Choline chloride can be used for microwave application and de-
composes detectably only with very energy pulses like g-irradiation.
Wt
Weight
◦
Keeping choline chloride for two weeks at 60 C in 1 N NaOH
solution lead to a negligible loss of 4 ppm underlining the stability
of the quaternary ammonium compound, see: C. Lester and P.
Jose, J. Pharm. Sci., 1982, 71, 470. TGA showed a decomposition
Acknowledgements
◦
temperature Tdec ~ 300 C, see: Y. Fukaya, Y. Iizuka, K. Sekikawa
We thank the S u¨ dzucker AG and the Fachagentur Nachwach-
sende Rohstoffe for the support of the project. F. I. thanks
the German Federal Environmental Foundation (DBU) for a
graduate scholarship and A. P. thanks the Fonds der Chemischen
Industrie for a thesis fellowship.
and H. Ohno, Green Chem., 2007, 9, 1155.
2 Furthermore, Abbott et al. described choline chloride/urea mixtures,
which were characterized as greener media for chemical syntheses
and processes by Avalos et al. Hence, its properties can make choline
chloride a suitable media for our HMF synthesis: A. P. Abbott, G.
Capper, D. L. Davies, R. K. Rasheed and V. Tambyrajah, Chem.
Commun., 2003, 70–71; M. Avalos, R. Babiano, P. Cintas, J. L.
Jim e` nez and J. C. Palacios, Angew. Chem., Int. Ed., 2006, 45, 3904–
3
908.
3 X. Qi, M. Watanabe, T. M. Aida and R. L. Smith Jr., Green Chem.,
008, 10, 799.
Notes and references
2
1
Y. R o´ man-Leshkov, C. J. Barrett, Z. Y. Liu and J. A. Dumesic, Nature,
24 The use of 10 mol% of catalysts was found to be optimal.
Lower catalyst loadings lead to slower conversions and increasing
amounts of side products. A recycling of the catalysts was not
2
007, 447, 982.
2
3
B. Kamm, Angew. Chem., Int. Ed., 2007, 46, 5056.
Y. R o´ man-Leshkov, J. N. Chheda and J. A. Dumesic, Science, 2006,
considered, as during aqueous workup Lewis acids, such as FeCl
3
,
3
12, 1933.
hydrolyze.
4
5
D. Peters, Chem. Ing. Tech., 2006, 78(3), 229.
25 The melt mixture is very hygroscopic. The melting point of the
mixture in reactions was therefore found to be much lower.
26 T. Wu and S. Zivanovic, Carbohydr. Polym., 2008, 73, 248.
27 S. Hu, Z. Zhang, Y. Zhou, J. Song, H. Fan and B. Han, Green Chem.,
2009, 11, 873.
M. Bicker, D. Kaiser, L. Ott and H. Vogel, J. Supercrit. Fluids, 2005,
3
6, 118.
6
7
G. W. Huber, J. N. Chheda, C. J. Barrett and J. A. Dumesic, Science,
005, 308, 1446.
Y. Nakamura and S. Morikawa, Bull. Chem. Soc. Jpn., 1980, 53,
705.
2
28 [C mim]Cl was used by Yong et al. in combination with NHC-
4
3
M complexes (N-heterocyclic carbine-metal complexes). The N-
heterocyclic carbine/metal complexes were prepared by heating a
mixture of imidazolium salts, potassium tert-butoxide and metal
chloride in dimethylformamide, see ref. 15. Since this first screening
study does not involve the used catalysts used in all evaluated alter-
native reaction media, the NHC-M complexes were not considered
further.
8
9
K. Seri, Y. Inoue and H. Ishida, Chem. Lett., 2000, 22.
K. Seri, Y. Inoue and H. Ishida, Bull. Chem. Soc. Jpn., 2001, 74,
1
2
2
145; F. S. Asghari and H. Yoshida, Carbohydr. Res., 2006, 341,
379; F. S. Asghari and H. Yoshida, Ind. Eng. Chem. Res., 2006, 45,
163.
1
1
0 L. Rigal, A. Gaset and J. P. Gorrichon, Ind. Eng. Chem. Prod. Res.
Dev., 1981, 20, 719; S. Hu, Z. Zhang, Y. Zhou, B. Han, H. Fan, W.
Li, J. Song and Y. Xie, Green Chem., 2008, 10, 1280; J. N. Chedda,
Y. R o´ man-Leshkov and J. A. Dumesic, Green Chem., 2007, 9,
29 Online material safety data sheets from Merck, Sigma-Aldrich, Roth,
IoLiTec as of February 2009. In the case of the investigated ionic
liquids, further literature references were consulted: L. Ropel, L. S.
Belv e` ze, S. N. V. Aki, M. A. Stadtherr and J. F. Brennecke, Green
Chem., 2005, 7, 83; J. Ranke, S. Stolte, R. Stoermann, J. Arning and
B. Jastorff, Chem. Rev., 2007, 107, 2183.
3
42.
1 A. Stark, B. Ondruschka, and J. Lifka, AZ 10 2008 009 9933.3,
applied for: 18.02.2008.
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Green Chem., 2009, 11, 1948–1954 | 1953