US3515748A

US3515748A - Preparation of aromatic carboxylic acids and nitro - substituted aromatic carboxylic acids

Info

Publication number: US3515748A
Application number: US452011A
Authority: US
Inventors: Danford H Olson; Phillip W Storms
Original assignee: Marathon Oil Co
Current assignee: Marathon Oil Co
Priority date: 1965-04-29
Filing date: 1965-04-29
Publication date: 1970-06-02
Anticipated expiration: 1987-06-02

Description

United States Patent Office 3,515,748 Patented June 2, 1970 3,515,748 PREPARATION OF AROMATIC CARBOXYLIC ACIDS AND NITRO SUBSTITUTED ARO- MATIC CARBOXYLIC ACIDS Danford H. Olson and Phillip W. Storms, Littleton, Colo., assignors to Marathon Oil Company, Findlay, Ohio, a corporation of Ohio No Drawing. Filed Apr. 29, 1965, Ser. No. 452,011 Int. Cl. C07c 79/46, 63/02 US. Cl. 260515 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved method of preparing aromatic carboxylic acids and/or nitro-substituted aromatic carboxylic acids. In particular, the present invention relates to the preparation of benzene carboxylic acids and/or nitro-substituted benzene carboxylic acids. In its more specific and especially preferred aspects, the present invention relates to an improved method of preparing nitrobenzoic acids, particularly mononitrobenzoic acids such as para-nitrobenzoic acid.

Vairous methods of preparing nitrobenzoic acids, for example, have long been known. Generally speaking, these prior art methods involve the steps of first nitrating a suitable aromatic compound and then oxidizing the nitrated compound to form the desired nitrobenzoic acid. Thus, for example, in preparing a mononitro-substituted nitrobenzoic acid such as para-nitrobenzoic acid in accordance with prior art practices, toluene is first nitrated to form the corresponding nitrotoluene. The nitrotoluene is then oxidized to obtain the desired paranitrobenzoic acid. So far as is known, no adequately satisfactory method of preparing nitrobenzoic acids, especially mononitro-substituted nitrobenzoic acids exemplified particularly .by para-nitrobenzoic acid, heretofore has been developed which avoids a multiple step procedure of the general type outlined above.

In accordance with the present invention, it have been discovered that nitrobenzoic acids, especially mononitrobenzoic acids, can be prepared in substantial yields by the direct and essentially simultaneous oxidation and nitration of certain types of aromatic compounds under conditions hereafter described in detail. The reaction goes to substantial completion in a single step and the nitrobenzoic acid formed is thereafter recovered by conventional product separation procedures.

In achieving the objectives of this invention, a reaction mixture of the aromatic compound is formed with a nitrating agent in the presence of a sulfoxide. The sulfoxide is believed to form a complex with the nitrating agent which actively participates in the oxidation-nitration reaction. The aromatic compounds having utility in the practice of the invention are characterized in that they have at least one substituent attached directly to the aromatic ring or nucleus which is capable, in the described reaction mixture, of conversion to carboxyl without substantial interference with the nitration of the aromatic nucleus.

In accordance with the especially preferred aspects of the present invention, any benzene compound containing an activating group can be utilized. An activating group can be defined as any group which makes substitu tion reactions proceed easier than on benzene itself and directs substitution predominantly to ortho and para positions. Exemplary of such groups are primary and secondary alkyl groups and derivatives thereof. The derivatives of alkyl benzenes advantageously are of the benzylic type and may include benzene hydroperoxides.

In accordance with the particularly preferred aspects of the present invention, in utilizing the method of the invention to prepare mononitro-substituted nitrobenzoic acids such as paranitrobenzoic acid, the aromatic compound employed should be monosubstituted and the substituent should be either an alkyl group, for example, or especially desirably, a group of the benzylic type described hereinabove.

A Wide choice of aromatic compounds is available for the purposes of carrying out the method of the present invention. Exemplary of aromatic compounds having particular utility in the preparation of a mononitrobenzoic acid such as para-nitrobenzoic acid are lower alkyl aromatics such as toluene, phenylethane, phenylpropanes and phenylbutanes; aromatic alcohols exemplified by benzyl alcohol, phenacyl alcohol, benzhydrol, and 2-phenyl-2-propanol; aromatic halides such as benzyl chloride and benzyl bromide; aromatic hydroperoxides such as c-umene hydroperoxide and benzyl hydroperoxide; aromatic esters exemplified by benzyl acetate and benzyl formate, and the like. The aromatic compounds utilized in preparing nitrobenzoic acids in accordance with the practice of the present invention may contain substituents other than the described activating group. The primary considerations in the selection of such an aromatic compound for this purpose are the susceptibility of the substituent, or substituents, thereon, other than the described activating group, to oxidation under the conditions of the reaction, and, less importantly, steric hinderance characteristics of the substituent. In addition to the foregoing aromatic compounds, various lower polyalkyl substituted aromatics can be utilized to prepare a wide variety of nitro-substituted aromatic carboxylic acids. The alkyl substituents advantageously should contain from 1 to 5 carbon atoms and should be positioned with relation to one another on the aromatic nucleus to favor nitration. Xylenes are particularly suitable for this purpose. It should be noted that, in carrying out the reaction with any of the aforementioned aromatic compounds, the position of the substituent on the aromatic nucleus with relation to the activating group thereon will influence the. position on the aromatic nucleus at which the nitro group attaches.

The nitrating agent employed in the method of the present invention should be capable of furnishing nitronium ion and, concomitantly, of complexing with the sulfoxide used in forming the reaction mixture. Of especial utility in this connection is dinitrogen tetroxide. This compound is available commercially in various grades, but advantageously is used in a substantially pure form. Apart from dinitrogen tetroxide, nitric acid also can be used as the nitrating agent. The nitric acid may vary considerably in strength. Good results can be attained with aqueous solutions of nitric acid of strength of from about 32 to 86%, with especially desirable results being obtained with aqueous solutions containing from about 50 to weight percent of nitric acid.

The proportions of aromatic compound and nitrating agent utilized in the method of the present invention can be varied Within appreciable limits and will, in the main, be determined by the character of the aromatic compound and nitrating agent involved in the nitration reaction. Thus, for example, in forming a reaction mixture of toluene with dinitrogen tetroxide as the nitrating agent, approximately stoichiometric or theoretical proportions of toluene and dinitrogen tetroxide, that is, a tolu cue to dinitrogen tetroxide molar ratio of about 1:3, are used. When forming a reaction mixture of toluene with nitric acid as the nitrating agent, on the other hand, a molar ratio of about 1 of toluene to 4 of nitric acid is employed. In accordance with the preferred practice of the invention, it has been found advantageous to employ a slight excess, of the order of 5 to over stoichiometric or theoretical proportions, of the nitrating agent.

As indicated hereinabove, the objectives of the present invention are attained by carrying out the reaction between the aromatic compound and the nitrating agent in the presence of a sulfoxide of the type having a formula corresponding to wherein Rand R are the same or difi'ere'nt, and may be alkyl or aryl. Dimethylsulfoxide is especially useful for this purpose. Other sulfoxides that can be used are diethylsulfoxide, methylsulfinylethane, methylsulfinylpropane, methylsulfinylbutane, diphenylsulfoxide, phenylsulfinylethane, and the like, and compatible mixtures of the same.

Apart from its function of reacting with the nitrating agent to form a complex which acts as a carrier for the nitronium ion furnished by the nitrating agent thereby to facilitate nitration of the aromatic compound, the sulfoxide advantageously also is used in the method of this invention to provide a medium for carrying out the oxidation-nitration reaction. More specifically, in this latter connection, due to the exothermic character of the reaction, the volume of the sulfoxide utilized can be regulated in a manner to enable the reaction mixture to be maintained within a temperature range most favorable to the formation of the nitrobenzoic acid. In accordance with the preferred practice of this invention, preparation of the reaction mixture is initiated by first introducing the aromatic compound into the sulfoxide. Similarly, particularly when dinitrogen tetroxide is used, the nitrating agent is separately incorporated into a suitable volume of the sulfoxide. The temperature of the reaction mixture advantageously can then be controlled by adding the sulfoxide solution of the nitrating agent to the aromatic compound solution gradually or in increments.

The temperature at which the method of the present invention is carried out may range from about 40 degrees C. to about 100 degrees C., more advantageously from degrees C. to 80 degrees C., with about 75 degrees C. being especially preferred. While not required, temperature control equipment can be utilized to assure control of the temperature of the reaction mixture within the ranges indicated.

'While the method of the present invention has been described with reference to its particular utility in the preparation of nitro-substitu ted aromatic compounds, especially nitro-substituted benzene compounds, the method also can be used to advantage in the preparation of aromatic carboxylic acids. In accordance with this aspect of the invention, any benzene compound containing a deactivating group can be defined as any group which, under the conditions of the described reaction, is converted to a carboxyl group and does not influence nitration on the benzene ring. Exemplary of compounds containing such a deactivating group are aromatic ketones exemplified by acetophenone, ethylphenylketone, and benzophenone; aromatic aldehydes such as benzaldehyde and m-tolualdehyde; aromatic esters exemplified by methylbenzoate and ethylbenzoate; and aromatic amides such as benzamide. In carrying out the reaction of this invention with an aromatic compound containing both an activating group and a deactivating group as defined hereinabove, the nature of the product, or products, ob

tained would be determined by the group which had the greatest elfect.

In order that the full details of the present invention will be even better understood, the following examples are provided. These examples are illustrative of the practice of the method of the invention and it should be understood that variations may be made therein in a number of particulars without in any way departing from the fundamental principles and teachings provided herein. The examples, therefore, are not to be construed in any way as limitative of the scope of the invention.

Example 1 Example 2 To a solution of 0.1 gram-mole of cumene hydrot peroxide in 150 ml. of dimethylsulfoxide is addeda solution of 0.163 gram mole of dinitrogen tetroxide .in 50 ml. of dimethylsulfoxide. The addition rate is regulated to maintain the reaction temperature at 50 degrees, C. The; reaction mixture is stirred for one hour and the dimethyli sulfoxide is then removed by distillation in vacuo. A solid product weighing 14.7 grams is obtained. The solid product is dissolved in 25 ml. of a 10 percent sodium hydroxide solution and washed with ether. Acidification of the caustic solution yields a solid which is purified by sublimation. The pure product is identified as para-nitrobenzoic acid.

Example 3 To a solution of 0.1 gram mole of cumene hydroperoxide in 150 ml. of methylsulfinylethane at 20 degrees C. is added slowly a solution of 0.16 gram mole of dinitrogen tetroxide in 50 ml. of methylsulfinylethane. The temperature of the reaction rises to 5060 degrees C. where it is maintained by controlled rate of addition of the dinitrogen tetroxide solution. After addition of the dinitrogen tetroxide solution is completed, the solution is stirred for one hour. The methylsulfinylethane and excess.

dinitrogen tetroxide are evaporated in vacuo leaving 15.1 grams of a solid product which is base-soluble. The product is identified as para-nitrobenzoic acid by its infrared spectrum compared to that of an authentic sample;

yield 88.3%.

Example 4 To a solution of 0.1 gram mole of cumene hydroperoxide in 150 ml. of dimethylsulfoxide, 15 grams (0.16 gram mole) of 70% nitric acid in 25 ml. of dimethylsulfoxide is added dropwise. The temperature of the reaction mixture rises to degrees C. and is maintained at that temperature until all of the nitric acid solution is added. The mixture is stirred for 30 minutes and isathen evaporated in vacuo. The resulting solid product is dissolved in 20 ml. of a 10 percent solution of sodium hydroxide and washed with ether. Acidification of the canstic solution yields a solid which is purified by sublimation. The pure product is identified as para-nitrobenzoic acid.

Example 5 A stream of dinitrogen tetroxide is passed into a solution of 25 g. of m-xylene in 150 ml. of dimethylsulfoxide at degrees C. for 2 hours. The excess dinitrogen tetroxide is removed with a stream of nitrogen and the solution is poured into 200 ml. of water and made basic with sodium carbonate. The solution is extracted with methylene chloride and the aqueous solution is evaporated to dry salts. The salts are acidified With concentrated hydrochloric acid and again evaporated to dryness. The dry acid salts are washed with isopropyl alcohol. The alcohol solution is evaporated to dryness giving a yellow solid. The solid is dissolved in aqueous sodium carbonate and the solution is acidified with hydrochloric acid. A yellow precipitate is slowly formed which is filtered and dried. Infrared and nuclear magnetic resonance spectra show the yellow solid to be m-toluic acid containing 4-nitro and 6-nitro-m-toluic acids.

Example 6 To a solution of 0.1 gram-mole of meta-tolualdehyde in 150 ml. of dimethylsulfoxide is added 0.16 gram-mole of dinitrogen tetroxide in 100 ml. of dimethylsulfoxide. The procedure outlined in Example 2 is followed. The product obtained is identified as m-toluic acid.

Example 7 To a solution of 0.1 gram-mole of 2 methylacetophenone in 150 ml. of dimethylsulfoxide is added a solution of 0.15 gram-mole of dinitrogen tetroxide in 50 ml. of dimethylsulfoxide. The procedure outlined in Example 2 is followed. The product obtained is identified as otoluic acid.

While the invention has been described in detail, it should be understood that various modifications may be made in the light of the teachings hereof without departing from the spirit and scope of the invention.

What is claimed is:

1. A method of preparing nitrobenzoic acid comprising forming a reaction mixture consisting essentially of a substituted benzene compound, a nitrating agent selected from the group consisting of dinitrogen tetroxide and nitric acid, and a di-lower alkyl sulfoxide solvent, the benzene compound having at least one substituent on the benzene nucleus, said at least one substituent being characterized in that it contains a benzylic carbon atom with at least one hydrogen or oxygen attached directly to the benzylic carbon atom, allowing the reaction to proceed at a temperature of from about 40 C. to about 100 C., and recovering the nitrobenzoic acid formed.

2. A method of preparing nitrobenzoic acids comprising forming a reaction mixture consisting essentially of a substituted benzene compound, a nitrating agent selected from the group consisting of dinitrogen tetroxide and nitric acid, and a di-lower alkyl sulfoxide solvent, the benzene compound having at least one substituent of the benzylic type, allowing the reaction to proceed at a temperature of from about 40 C. to about 100 C., and recovering the nitrobenzoic acid formed.

3. A method of preparing benzene carboxylic acids comprising forming a reaction mixture consisting essentially of a substituted "benzene compound and the reaction product of a nitrating agent selected from the group consisting of dinitrogen tetroxide and nitric acid, and a di-lower alkyl sulfoxide solvent, the benzene compound having at least one substituent attached directly to the aromatic nucleus, said at least one substituent being characterized in that it contains a benzylic carbon atom with at least one hydrogen or oxygen attached directly to the benzylic carbon atom, allowing the reaction to proceed at a temperature in the range of from about 40 C. to about 100 C., and recovering the benzene carboxylic acid formed.

4. A method of preparing nitrobenzoic acids comprising forming a reaction mixture consisting essentially of a substituted benzene compound and the reaction product of a di-lower alkyl sulfoxide solvent and a nitrating agent selected from the group consisting of dinitrogen tetroxide and nitric acid, the benzene compound having at least one substituent attached directly to the aromatic nucleus, said at least one substituent being characterized in that it contains a benzylic carbon atom with a least one hydrogen or oxygen attached directly to the benzylic carbon atom, allowing the reaction to proceed at a temperature of from about 40 degrees to 100 degrees C., and recovering the nitrobenzoic acid formed.

5. A method of preparing para-nitrobenzoic acid comprising forming a reaction mixture consisting essentially of a mono-substituted mononucleated benzene compound and a reaction product of a nitrating agent selected from the group consisting of dinitrogen tetroxide and nitric acid, and a di-lower alkyl sulfoxide solvent, the substituent on the benzene compound being characterized in that it contains a benzylic carbon atom with at least one hydrogen or oxygen attached directly to the benzylic carbon atom, allowing the reaction to go to substantial completion at a temperature of from about 40 C. to about 100 C., and recovering the para-nitrobenzoic acid formed.

6. A method of preparing para-nitrobenzoic acid comprising forming a reaction mixture consisting essentially of a mono-substituted mononucleated benzene compound, dinitrogen tetroxide and dimethylsulfoxide, the substituent on the benzene compound being characterized in that it contains a benzylic carbon atom with at least one hydrogen or oxygen attached directly to the benzylic carbon atom, allowing the reaction to proceed at a temperature of from about 40 C. to about 100 C., and recovering the para-nitrobenzoic acid formed.

7. A method of preparing para-nitrobenzoic acid comprising a reaction mixture consisting essentially of cumene hydroperoxide, a nitrating agent selected from the group consisting of dinitrogen tetroxide and nitric acid, and a di-lower alkyl sulfoxide solvent, allowing the reaction to proceed at a temperature of from about 40 C. to about 100 C., and recovering the para-nitrobenzoic acid formed.

8. A method of preparing para-nitrobenzoic acid comprising forrning a reaction mixture consisting essentially of toluene, a nitrating agent selected from the group consisting of dinitrogen tetroxide and nitric acid, and a dilower alkyl sulfoxide solvent, allowing the reaction to proceed at a temperature of from about 40 C. to about 100 C., and recovering the para-nitrobenzoic acid formed.

9. A method of preparing nitrobenzoic acid comprising forming a reaction mixture consisting essentially of xylene, dinitrogen tetroxide and dimethylsulfoxide, allowing the reaction to proceed at a temperature of from about 40 C. to about 100 C., and recovering the nitrobenzoic acid formed.

10. A method of preparing para-nitrobenzoic acid comprising forming a reaction mixture of cumene hydroperoxide and dinitrogen tetroxide in the presence of dimethylsulfoxide, maintaining the reaction at a temperature of from about 40 degrees C. to 100 degrees C. until the reaction has gone to substantial completion, and recovering the para-nitrobenzoic acid formed.

11. A method of preparing para-nitrobenzoic acid comprising forming a reaction mixture of cumene hydroperoxide and dinitrogen tetroxide in the presence of dimethylsulfoxide, allowing the reaction to proceed at a temperature of about degrees C., and recovering the paranitrobenzoic acid formed.

References Cited UNITED STATES PATENTS 9/ 1966 Bartholome et a1 260524 OTHER REFERENCES JAMES A. PATTEN, Primary Examiner U .8. Cl. X.R. 260-524 Patent NO. 3, 515,148 Dated June 2, 1970 Danford H. Olson and Phillip W. Storms Inventor(s) It is certified that error appears in the above-identified patent and LhaL said Letters Patent are hereby corrected as shown below:

Col. 1, line 16: "aromaic should read -aromatic Col. 1, line 52: "have' should read -has-- Col', 3, line 64: should read -ing a "deactivating group" can be utilized. A "deactivating group" may be defined as any group Signed and sealed this 18th day of January 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GQTTSCHALK Attesting Officer Acting Commissioner of Patents