Synthesis of lactam based ionic liquid

Abstract

Lactamium based ionic liquids are described. They comprise at least one of: the reaction product of a lactam compound having a formula (IV) ##STR00001## wherein n is 1, 2 or 4 to 8, and a Brøsted acid HX; or a Brøsted acid HX, where X is a halide, and a metal halide; where the reaction product is p-toluenesulfonate, halide, or the halometallate; or the reaction product of a lactam compound having a formula (V) ##STR00002## wherein the ring has at least C—C one double bond, and n is 1 to 8, and a Brøsted acid HX; or a Brøsted acid HX, where X is a halide, and a metal halide; or the reaction product of a lactam compound having a formula (VI) ##STR00003## wherein n is 1 to 8, m is 1 to 8, and the rings can be saturated or unsaturated; and a Brøsted acid HX; or a Brøsted acid HX, where X is a halide, and a metal halide.

Claims

1. A lactamium based ionic liquid selected from the group consisting of: a reaction product of a lactam compound having formula ##STR00022## wherein n is 1, and a Brønsted acid HX; or a Brønsted acid HX, where X is a halide, and a metal halide; where the reaction product is a halide, or a halometallate.

2. A method of making a lactamium based ionic liquid comprising: reacting a lactam compound having formula ##STR00023## wherein n is 1, with a Brønsted acid HX; or a Brønsted acid HX, where X is a halide, and a metal halide; where the reaction product is a halide, or a halometallate.

3. The method of claim 2 wherein the lactam compound has the general formula (IV).

4. The method of claim 2 wherein the reaction takes place in a solvent.

5. The method of claim 4 wherein the solvent comprises water, toluene, dichloromethane, liquid carboxylic acids, alcohols, or combinations thereof.

6. The method of claim 2 wherein a ratio of the Brønsted acid HX to the lactam compound is about 1:1 to about 3:1.

7. A lactamium based ionic liquid, the ionic liquid having formula: ##STR00024## wherein n is 1, and X.sup.− is an anion group of a Brønsted acid HX or a halometallate, and wherein is X.sup.− is halide, or the halometallate.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention provides cost effective ionic liquids capable of being produced on an industrial scale. The ionic liquids are lactamium based ionic liquids. Lactam compounds can be converted to ionic liquids through reactions with strong acids followed by a second reaction with a metal halide if needed. Lactamium based ionic liquids can be used in numerous applications and can have an economic benefit.

(2) One type of lactamium based ionic liquid has the formula:

(3) ##STR00013##

(4) wherein n is 1 to 8, and X.sup.− is an anion group of a Brøsted acid HX or a halometallate, and wherein is X.sup.− is p-toluenesulfonate, halide, or the halometallate, with the proviso that when n is 3, X.sup.− is not a zinc halometallate.

(5) Another way to represent this compound is:

(6) ##STR00014##

(7) wherein n is 1 to 8, and X.sup.− is an anion group of a Brøsted acid HX or a halometallate, and wherein is X.sup.− is p-toluenesulfonate, halide, or the halometallate, with the proviso that when n is 3, X.sup.− is not a zinc halometallate.

(8) Formula (I) is intended to cover both representations.

(9) Suitable halides include, but are not limited to, bromide, chloride, and iodide.

(10) Halometallates are mixtures of halides, such as bromide, chloride, and iodide, and metals. Suitable metals include, but are not limited to, Sn, Al, Zn, Mn, Fe, Ga, Cu, Ni, and Co. In some embodiments, the metal is aluminum, with the mole fraction of aluminum ranging from 0<Al<0.25 in the anion. Suitable anions include, but are not limited to, AlCl.sub.4.sup.−, Al.sub.2Cl.sub.7.sup.−, Al.sub.3Cl.sub.10.sup.−, AlCl.sub.3Br.sup.−, Al.sub.2Cl.sub.6Br.sup.−, Al.sub.3Cl.sub.9Br.sup.−, AlBr.sub.4.sup.−, Al.sub.2Br.sub.7.sup.−, Al.sub.3Br.sub.10.sup.−, GaCl.sub.4.sup.−, Ga.sub.2Cl.sub.7.sup.−, Ga.sub.3Cl.sub.10.sup.−, GaCl.sub.3Br.sup.−, Ga.sub.2Cl.sub.6Br.sup.−, Ga.sub.3Cl.sub.9Br.sup.−, CuCl.sub.2.sup.−, Cu.sub.2Cl.sub.3.sup.−, Cu.sub.3Cl.sub.4.sup.−, ZnCl.sub.3.sup.−, FeCl.sub.3.sup.−, FeCl.sub.4.sup.−, Fe.sub.3Cl.sub.7.sup.−, PF.sub.6.sup.−, and BF.sub.4.sup.−.

(11) Another type of lactamium based ionic liquid has the formula:

(12) ##STR00015##

(13) wherein the ring has at least one C—C double bond, n is 1 to 8, and X.sup.− is an anion group of a Brøsted acid HX or a halometallate.

(14) The ring has at least one C—C double bond. Larger rings may have more than one C—C double bond. The C—C double bond(s) can be between any two adjacent carbons capable of forming a double bond.

(15) Suitable X.sup.− groups include, but are not limited to, carboxylates, nitrates, phosphates, phosphinates, phosphonates, imides, cyanates, borates, sulfates (including bisulfates), sulfonates (including fluoroalkanesulfonates), acetates, halides, halometallates, and combinations thereof. Examples of X.sup.− groups include, but are not limited to, tetrafluoroborate, triflate, trifluoroacetate, chloroacetate, nitrate, hydrogen sulfate, hydrogen phosphate, dicyanoimide, methylsulfonate, and combinations thereof.

(16) Another way to represent this compound is

(17) ##STR00016##

(18) wherein the ring has at least one C—C double bond, n is 1 to 8, and X.sup.− is an anion group of a Brøsted acid HX or a halometallate.

(19) Formula (II) is intended to cover both representations.

(20) Examples of Formula (II) ionic liquids include, but are not limited to, 1,5-dihydro-pyrrol-2-one based ionic liquids, and 1,3-dihydro-2H-pyrrol-one based ionic liquids.

(21) Another type of lactamium based ionic liquid has the formula:

(22) ##STR00017##

(23) wherein n is 1 to 8, m is 1 to 8, X.sup.− is an anion group of a Brøsted acid HX or a halometallate, and the rings can be saturated or unsaturated.

(24) The heterocyclic ring (ring with n) can be saturated or unsaturated. The hydrocarbon ring (ring with m) can be saturated, unsaturated, or aromatic. If the ring is unsaturated, the C—C double bond can be between any two carbons capable of forming a double bond. There can be one or more C—C double bonds in either ring or in both rings.

(25) Another way to represent this compound is

(26) ##STR00018##

(27) wherein n is 1 to 8, m is 1 to 8, X.sup.− is an anion group of a Brøsted acid HX or a halometallate, and the rings can be saturated or unsaturated.

(28) The heterocyclic ring (ring with n) can be saturated or unsaturated. The hydrocarbon ring (ring with m) can be saturated, unsaturated, or aromatic. If the ring is unsaturated, the C—C double bond can be between any two adjacent carbons capable of forming a double bond. There can be one or more C—C double bonds in either ring or in both rings.

(29) Formula (III) is intended to cover both representations.

(30) Examples of Formula (III) ionic liquids include, but are not limited to, octahydro-2H-indol-2-one ionic liquids, and 2-oxindole ionic liquids.

(31) A lactamium based ionic liquid can be made by reacting a lactam compound having a formula

(32) ##STR00019##

(33) wherein n is 1 to 8,

(34) with a Brøsted acid HX; or a Brøsted acid HX where X is a halide, and a metal halide; where the reaction product is p-toluenesulfonate, halide, or the halometallate. In some embodiments, when n is 3, the reaction product is not a zinc halometallate.

(35) Another lactamium based ionic liquid can be made by reacting a lactam compound having a formula

(36) ##STR00020##

(37) wherein the ring has at least one C—C double bond, and n is 1 to 8,

(38) with a Brøsted acid HX; or a Brøsted acid HX, where X is a halide, and a metal halide.

(39) Another lactamium based ionic liquid can be made by reacting a lactam compound having a formula

(40) ##STR00021##

(41) wherein n is 1 to 8, m is 1 to 8, and the rings can be saturated or unsaturated;

(42) with a Brøsted acid HX; or a Brøsted acid HX, where X is a halide, and a metal halide.

(43) The heterocyclic ring (ring with n) can be saturated or unsaturated. The hydrocarbon ring (ring with m) can be saturated, unsaturated, or aromatic. If the ring is unsaturated, the C—C double bond can be between any two adjacent carbons capable of forming a double bond. There can be one or more C—C double bonds in either ring or in both rings.

(44) In some embodiments, when making a halometallate, the lactam compound is reacted with a Brøsted acid HX, such as HCl, where X is a halide, to form a lactamium halide. The lactamium halide is then reacted with a halometallate to form the lactamium halometallate. In one embodiment, when a lactam compound having the formula (I) and n is 3 is reacted, the lactam compound is reacted with a Brøsted acid HX, such as HCl, to form a lactamium halide. The lactamium halide is then reacted with a metal halide to form the lactamium halometallate.

(45) As is understood by those of skill in the art, the particular Brøsted acid used will depend on the anion desired. Suitable Brøsted acids for use with lactam compound (IV) include for example, p-toluenesulfonic acid, hydrochloric acid, and hydrobromic acid. Suitable Brøsted acids HX for use with lactam compounds (V) and (VI) include, but are not limited to, at least one of sulfuric acid, p-toluenesulfonic acid, hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, tetrafluoroboric acid, triflic acid, trifluoroacetic acid, chloroacetic acid, and methanesulfonic acid.

(46) The reaction can take place at temperatures in the range of about −36° C. to the decomposition temperature of the ionic liquid, or about −20° C. to less than the decomposition temperature of the ionic liquid, or about 0° C. to about 200° C., or about 0° C. to about 150° C., or about 0° C. to about 120° C., or about 20° C. to about 80° C.

(47) The reaction typically takes place at atmospheric pressure, although higher or lower pressures could be used if desired.

(48) When making halometallate compounds, the reaction should take place in an inert atmosphere.

(49) The reaction typically takes about 1 min to multiple days, depending on the ionic liquid. Those made with the Brøsted acid typically take minutes to hours, while the halometallates typically take minutes to one or more days.

(50) The reaction may be practiced in laboratory scale experiments through full scale commercial operations. The process may be operated in batch, continuous, or semi-continuous mode.

(51) Typically, the ratio of the Brøsted acid to the lactam compound is about 1:1 to about 3:1. In some embodiments, prior to making a halometallate, a lactamium halide is formed using a Brøsted acid, the ratio of Brøsted acid to the lactam compound is about 1:1.

(52) In some embodiments, the reaction can take place in the absence of a solvent. In other embodiments, it can take place in the presence of a solvent. Suitable solvents for non-halometallate ionic liquids include, but are not limited to, water, toluene, dichloromethane, liquid carboxylic acids, such as acetic acid or propanoic acid, alcohols, such as methanol and ethanol, and combinations thereof. When water is used as the solvent, an additional product may form. The products can be separated using known separation techniques. Non-protic solvents, such as dichloromethane, are suitable for use with halometallates.

(53) By the term “about,” we mean within 10% of the value, or within 5%, or within 1%.

EXAMPLES

Example 1: Preparation of Caprolactamium p-toluenesulfonate

(54) In a 20 mL vial, 1.05 g (9.2 mmol) of caprolactam was melted at 80° C. with stirring. p-toluene sulfonic acid monohydrate (9.0 mmol) was added to the caprolactam melt. After stirring for 0.75 h, volatiles were removed. Yield: 2.39 g (92.6%). The product was dissolved in dichloromethane, filtered, and volatiles were removed. .sup.1H NMR (500 MHz, d.sub.6-DMSO): 1.46-1.63 (m, 8H), 2.27 (s, 3H), 2.38 (t, 2H), 3.11 (t, 2H), 7.16 (d, 2H), 7.55 (d, 2H), 8.24 (broad s). .sup.13C NMR (125 MHz, d.sub.6-DMSO): 21.21, 22.95, 29.17, 30.08, 35.46, 42.28, 55.28, 125.91, 128.87, 139.32, 144.25, 179.44.

Example 2: Preparation of Caprolactamium Chloride

(55) In a 100 mL round bottom flask, a HCl solution (24.84, 0.22 mol) was added to a toluene solution of caprolactam (25.05 g, 0.22 mol). After stirring for 2 hours at room temperature, the volatiles were removed. Yield: 34.2 g. The solid was dissolved in dichloromethane, filtered, and volatiles were removed. .sup.1H NMR (500 MHz, d.sub.6-DMSO): 1.49-1.64 (m, 6H), 2.35 (t, 2H), 3.08 (t, 2H), 7.90 (broad s). .sup.13C NMR (125 MHz, d.sub.6-DMSO): 23.31, 29.78, 30.40, 36.16, 42.25, 178.90.

Example 3: Preparation of Caprolactamium Chloroaluminate

(56) All procedures were performed in a nitrogen glovebox. In a vial containing caprolactamium chloride (3.48 g, 0.23 mol), aluminum trichloride (6.37 g, 0.47 mol) was added slowly while stirring the mixture. After stirring for 5 hours, the mixture was allowed to settle and liquid was decanted. .sup.1H NMR (500 MHz, CDCl.sub.3): 1.85-1.94 (m, 6H), 2.90 (t, 2H), 3.63 (q, 2H), 8.07 (broad s). .sup.13C NMR (125 MHz, CDCl.sub.3): 23.31, 29.78, 30.40, 36.18, 42.24, 178.90.

(57) While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.