Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-02-15
2001-10-16
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C562S045000, C562S493000, C564S184000, C568S323000, C558S411000
Reexamination Certificate
active
06303812
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of isolating the products formed when certain haloaromatics are dehalogenated. In particular, it relates to the dilution of the reaction products with water to form separate phases followed by decantation.
In U.S. Pat. No. 5,886,210, Example 14(d), 2,3,5-trichloro4-methylmethylbenzoate (TCMMB) was mixed with elemental copper and propionic acid and reacted at about 130 to 135° C. to produce 3,5-dichloro4-methylmethylbenzoate (DCMMB). The product mixture was diluted with xylenes and filtered. The solids were washed with xylenes and the filtrates combined. The filtrates were washed with 1 M HCl and the product DCMMB was dried.
SUMMARY OF THE INVENTION
We have discovered that, under the conditions of this invention, adding water to a mixture containing a cuprous halide, a cuprous carboxylic acid salt, and certain dehalogenated aromatic products, such as DCMMB, will cause the mixture to separate into an organic phase containing the product and an aqueous phase containing copper salts; the two phases can be separated by decantation. (If the product has a high melting point, an inert solvent can be added to dissolve it prior to the addition of water to form the two phases.) This method of separating the components of the mixture is superior to the prior method because it is a simpler process since filtration is eliminated and usually no solvent is needed. For many purposes, the decanted product is sufficiently pure that it need not be distilled. Also, the copper in solution can be reduced to elemental copper and reused and the carboxylic acid can also be recovered.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Substrates useful in the dehalogenation reaction that forms the product mixture treated using the process of this invention have the general formula
where X is the halogen to be removed to form the product, R′ is COOH, COOR, COR, CN, COH(R)
2
, or SO
3
H, each R″ is independently selected from halogen, R, or OR or two vicinal R″ groups form one or more fused aromatic rings, R is alkyl from C
1
to C
18
or aryl from C
6
to C
18
, and n is 1 to 4. Preferably, X is chlorine, R′ is COOR, R is alkyl from C
1
to C
4
(most preferably methyl), R″ is a halogen (preferably chlorine) and/or methyl, and n is 2 as those compounds are commercially more important. More preferably, at least one R″ is a halogen (preferably chlorine) in the meta position as a solvent is usually not needed to dehalogenate those substrates. Examples of substrates useful in this invention include TCMMB, methyl-2,5-dichloro-4-methylbenzoate, 2,4-dichloroacetophenone, 2,5-dichlorobenzoic acid, methyl 2,5-dichlorobenzoate, 2,3-dichlorobenzoic acid, 2,5-dichlorobenzonitrile, and 2,5-dichlorobenzamide.
The elemental copper used in the dehalogenation reaction should be finely divided. About 1 to about 2.5 equivalents of copper should be used as less copper will leave too much unreacted substrate and more copper will leave too much unreacted copper. Preferably, about 1.7 to about 2.1 equivalents of copper are used.
Any carboxylic acid can be used in the dehalogenation reaction. Preferably, the carboxylic acid is a liquid at the reaction temperature. Examples of carboxylic acids that can be used include acetic acid, propionic acid, butyric acid, and benzoic acid. The preferred carboxylic acids are acetic acid and propionic acid as they are commercially available liquids and are not too malodorous. About 1.5 to about 3.5 equivalents of the carboxylic acid should be used per halogen to be removed as less is less effective and more is unnecessary and wasteful; preferably, about 1.9 to about 2.1 equivalents are used.
The dehalogenation reaction is best performed at or near the boiling point of the acid, but lower temperatures can be used if desired. For propionic acid, the temperature range can be about 100 to about 200° C., though about 140 to about 170° C. is preferred. The reaction normally requires about 2 to about 20 hours.
After the reaction is complete, the product mixture is cooled and water in an amount about 1 to about 5 times the weight of the substrate is added. Less water may not dissolve all the salts and more water is unnecessary. The preferred amount of water is about 1 to about 2 times the weight of the substrate. As an example, the product mixture can be cooled to about 80° C and hot water in an amount about equal to the substrate weight can be added so that the resulting temperature of the product mixture is about 40 to about 800° C.
If the product differs in density from the density of the aqueous solution formed by at least about 0.1 g/cc, then no solvent is needed and organic and aqueous phases will form, with the product in the organic phase and the copper salts in the aqueous phase. (If the product has a high melting point, a solvent can be used to dissolve it.) If the product is DCMMB and the carboxylic acid is propionic acid, the DCMMB will form a lower phase and the aqueous solution will form the upper phase. If the product does not differ in density from the density of the aqueous solution by at least about 0.1 g/cc, either a sufficient amount of a dense solvent, such as methylene chloride, chloroform, dichloroethane, or chlorobenzene, should be used so that the solution of the product is at least 0.1 g/cc denser than the aqueous solution, or a sufficient amount of a less dense solvent, such as hexane, toluene, or ethyl acetate, should be used so that the aqueous solution is at least 0.1 g/cc denser than the solution of the product. Alternatively, additional water may be added in order to lower the salt concentration in the aqueous phase, thus lowering its density. Preferably, the difference in densities should be at least about 0.2 g/cc so that the two phases form quickly.
The organic phase can be decanted and washed with water. The purity of the product in the organic phase may be high enough so that distillation is not needed. Elemental copper can be recovered from the aqueous phase by electrolysis. The carboxylic acid can be recovered from the aqueous phase by, for example, distillation.
REFERENCES:
patent: 5886210 (1999-03-01), Rayle
Derwin William S.
Fifolt Michael J.
Johnson David C.
Savidakis Michael C.
Spohn Ronald
Brookes Anne E.
Fuerle Richard D.
Killos Paul J.
Occidental Chemical Corporation
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