Ionic liquids and their use as solvents
Ionic compounds with a freezing point of up to 100° C. are formed by the reaction of an one amine salt of formula (I) R 1 R 2 R 3 R 4 N + X − , such as choline chloride with an organic compound (II) capable of forming a hydrogen bond with X; such as urea, wherein the molar ration of I to II is from 1:1.5 to 1:2.5. R 1 , R 2 , R 3 and R 4 may be H, optionally substituted C 1 to C 5 alkyl, optionally substituted C 6 to C 10 cycloalkyl, optionally substituted C 6 to C 12 aryl, optionally substituted C 7 to C 12 alkaryl, or R 1 and R 2 taken together may represent a C 4 to C 10 optionally substituted alkylene group, thereby forming with the N atom of formula I a 5 to 11-membered heterocyclic ring and all of R 1 , R 2 , R 3 and R 4 are not identical, X − may be NO 3 − , F, Cl − , Br − , I − , BF 4 − , ClO 4 − , CN − , SO 3 CF 3 − , or COOCF 3 − . The ionic compounds are useful as solvents, and electrolytes for example in electroplating, electrowinning, and electropolishing, and as catalysts.
1. An ionic compound, having a freezing point of up to 100° C. formed by the reaction of at least one amine salt of the formula
R 1 R 2 R 3 R 4 N + X − (I)
with at least one organic compound (II) which is capable of forming a hydrogen bond with X − , wherein R 1 , R 2 , R 3 and R 4 are each independently:-
H,
optionally substituted C 1 to C 5 alkyl,
optionally substituted C 6 to C 10 cycloalkyl,
optionally substituted C 6 to C 12 aryl
optionally substituted C 7 to C 12 alkaryl, or wherein
R 1 and R 2 taken together represent a C 4 to C 10 optionally substituted alkylene group, thereby forming with the N atom of formula (I) a 5 to 11-membered heterocyclic ring, X − , is NO 3 − , F − , Cl − , Br − , I − , BF 4 − , ClO 4 − , CN − , SO 3 CF 3 − , or COOCF 3 − , and wherein the term “optionally substituted” means that the group in question may or may not be substituted with one or more groups selected from OH, SH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , CHO, COR 5 and OR 5 , wherein R 5 is a C 1 to C 10 alkyl or cycloalkyl group,
wherein all of R 1 , R 2 , R 3 and R 4 are not identical, and
wherein compound (II) is a compound of the formula R 6 COOH, R 7 R 8 NH, R 9 CZNH 2 , or R 10 OH, wherein:-R 6 , R 7 , R 8 , R 10 are each H, a C 1 –C 8 alkyl group, an aryl group, or a C 7 –C 12 alkaryl group optionally substituted with from 0 to 6 group selected from OH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , COR 5 and OR 5 , wherein R 5 is H, a C 1 –C 10 alkyl or cycloalkyl group, R 9 is a C 1 –C 8 alkyl group, C 1 –C 12 an aryl group, or a C 7 –C 12 alkaryl group optionally substituted with from 0 to 6 groups selected from OH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , COR 5 and OR 5 , wherein R 5 is H, a C 1 to C 10 alkyl or cycloalkyl group, or wherein R 9 is NHR 11 , wherein R 11 is H or a C 1 –C 6 alkyl group, and Z is O and wherein formula (I) and compound (II) are utilized in a molar ration from 1:1.5 to 1:2.5
2. The ionic compound of claim 1 , wherein compound (II) is an organic compound which is solid at 20° C.
3. The ionic compound of claim 1 , wherein compound (II) is urea, acetamide, glyoxylic acid, malonic acid, oxalic acid dihydrate, trifluoroacetic acid, benzoic acid, benzyl alcohol, phenol p-methyl phenol, o-methyl phenol, m-methyl phenol, p-chloro phenol, D-fructose, or vanillin.
4. The ionic compound of claim 1 , wherein compound (II) is urea, aniline or a substituted aniline, a C 1 –C 6 hydroxyaliphatic acid, or a dicarboxylic acid of the formula HOOC(CH 2 ) n COOH, wherein n is 0 or 1, acetamide, a phenol or a substituted phenol, an alkylene glycol, or citric acid.
5. The ionic compound of claim 1 , wherein compound (II) is urea, acetamide; oxalic acid dihydrate, phenol, ethylene glycol, or citric acid.
6. The ionic compound of claim 1 , wherein compound (II) has a freezing point of less than 160° C.
7. The ionic compound of claim 5 , wherein compound (II) has a freezing point of 20° C. or less.
8. The ionic compound of claim 1 , wherein compound (II) contains only one type of functional group capable of acting as hydrogen bond donor.
9. The ionic compound of claim 1 , wherein the molar ratio of formula (I) to compound (II) is about 1:2.
10. The ionic compound of claim 1 , wherein R 4 is a C 1 to C 10 alkyl or a cycloalkyl group, substituted with at least one group selected from OH, Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , COR 5 , CHO and OR 5 .
11. The ionic compound of claim 1 , wherein each of R 1 , R 2 , R 3 , independently is a C 1 –C 5 alkyl or a cycloalkyl group, and R 4 is hydroxyl-alkyl.
12. The ionic compound of claim 7 , wherein each of R 1 , R 2 , R 3 , is methyl, and R 4 is hydroxyethyl.
13. The ionic compound of claim 1 , wherein X − is chloride.
14. The ionic compound of claim 1 , wherein R 1 , R 2 , R 3 , and R 4 have the one of following meanings
R 1
R 2
R 3
R 4
Me
Me
Me
C 2 H 4 OH
Me
Me
Benzyl
C 2 H 4 OH
Me
Me
Et
C 2 H 4 OH
Me
Me
Me
Benzyl
Me
Me
Me
C 2 H 4 OCOMe
Me
Me
Me
C 2 H 4 Cl
Me
Me
Me
ClCH 2 CHOHCH 2 (R)
Me
Me
Me
ClCH 2 CHOHCH 2 (S)
Me
H
H
H
Me
Me
H
H
Et
Et
Et
H
Et
Et
Et
Benzyl
Me
Benzyl
C 2 H 4 OH
C 2 H 4 OH
Me
H
H
CH 2 COOH
Me
Me
Me
BrC 2 H 4
Me
Me
Me
C 2 H 4 F
Me
Me
Me
Me(CH 2 ) 11
Et
Et
Et
Me
ET
Et
Et
Benzyl
Me
Me
C 2 H 4 OH
C 2 H 4 OH
15. A method of preparing an ionic compound, having a freezing point of up to 100° C., which method comprises reacting at least one amine salt of the formula
R 1 R 2 R 3 R 4 N +X − (I)
with at least one organic compound (II) which is capable of forming a hydrogen bond with X − , wherein R 1 , R 2 , R 3 and R 4 are each independently:-
H,
optionally substituted C 1 to C 5 alkyl,
optionally substituted C 6 to C 10 cycloalkyl,
optionally substituted C 6 to C 12 aryl,
optionally substituted C 7 to C 12 alkaryl, or wherein
R 1 and R 2 taken together represent a C 4 to C 10 optionally substituted alkylene group, thereby forming with the N atom of formula (I) a 5 to 11-membered heterocyclic ring, X − is NO 3 − , F − , Cl − , Br − , I − , BF 4 − , ClO 4 − , CN − , SO 3 CF 3 − , or COOCF 3 − , and wherein the term “optionally substituted” means that the group in question may or may not be substituted with one or more groups selected from OH, SH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , CHO, COR 5 and OR 5 , wherein R 5 is a C 1 to C 10 alkyl or cycloalkyl group,
wherein all of R 1 , R 2 , R 3 and R 4 are not identical, and
wherein compound (II) is a compound of the formula R 6 COOH, R 7 R 8 NH, R 9 CZNH 2 , or R 10 OH, wherein:-R 6 , R 7 , R 8 , R 10 are each H, a C 1 –C 8 alkyl group, an aryl group, or a C 7 –C 12 alkaryl group optionally substituted with from 0 to 6 groups selected from OH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , COR 5 and OR 5 , wherein R 5 is H, a C 1 to C 10 alkyl or cycloalkyl group, R 9 is a C 1 –C 8 alkyl group, C 1 –C 12 an aryl group, or a C 7 –C 12 alkaryl group optionally substituted with from 0 to 6 groups selected from OH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , COR 5 and OR 5 , wherein R 5 is H, a C 1 to C 10 alkyl or cycloalkyl group, or wherein R 9 is NHR 11 , wherein R 11 is H or a C 1 –C 6 alkyl group, and Z is O and wherein formula (I) and compound (II) have a molar ratio from 1:1.5 to 1:2.5.
16. The method of claim 15 , further comprising heating the amine salt of formula (I) with the compound (II).
17. A method of recovering a metal from a metal oxide, which method comprises forming a solution of the metal oxide in the ionic compound of claim 1 , and electrolysing the solution to recover the metal.
18. The method of claim 17 , wherein the metal is platinum or palladium.
19. A method of electropolishing a metal article, which method comprises immersing the metal article in the ionic compound of claim 1 , and applying a voltage to the metal article to electropolish the metal.
20. A method of forming a solution of a solute, which method comprises dissolving the solute in an ionic compound having a freezing point of up to 100° C., the said ionic compound being formed by the reaction of at least one amine salt of the formula
R 1 R 2 R 3 R 4 N +X − (I)
with at least one organic compound (II) which is capable of forming a hydrogen bond with X − , wherein R 1 , R 2 , R 3 and R 4 are each independently:-
H,
optionally substituted C 1 to C 5 alkyl,
optionally substituted C 6 to C 10 cycloalkyl,
optionally substituted C 6 to C 12 aryl,
optionally substituted C 7 to C 12 alkaryl, or wherein
R 1 and R 2 taken together represent a C 4 to C 10 optionally substituted alkylene group, thereby forming with the N atom of formula (I) a 5 to 11-membered heterocyclic ring, X − is NO 3 − , F − , Cl − , Br − , I − , BF 4 − , ClO 4 − , CN − , SO 3 CF 3 − , or COOCF 3 − , and wherein the term “optionally substituted” means that the group in question may or may not be substituted with one or more groups selected from OH, SH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , CHO, COR 5 and OR 5 , wherein R 5 is a C 1 to C 10 alkyl or cycloalkyl group,
wherein all of R 1 , R 2 , R 3 and R 4 are not identical, and
wherein compound (II) is a compound of the formula R 6 COOH, R 7 R 8 NH, R 9 CZNH 2 , or R 10 OH, wherein:-R 6 , R 7 , R 8 , R 10 are each H, a C 1 –C 8 alkyl group, an aryl group, or a C 7 –C 12 alkaryl group optionally substituted with from 0 to 6 groups selected from OH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , COR 5 and OR 5 , wherein R 5 is H, a C 1 to C 10 alkyl or cycloalkyl group, R 9 is a C 1 –C 8 alkyl group, C 1 –C 12 an aryl group, or a C 7 –C 12 alkaryl group optionally substituted with from 0 to 6 groups selected from OH, SR 5 , Cl, Br, F, I, NH 2 , CN, NO 2 , COOR 5 , COR 5 and OR 5 , wherein R 5 is H, a C 1 to C 10 alkyl or cycloalkyl group, or wherein R 9 is NHR 11 , wherein R 11 is H or a C 1 –C 6 alkyl group, and Z is O and wherein formula (I) and compound (II) have a molar ratio from 1:1.5 to 1:2.5.