2,960,544 United StatesPatent O. 1C6 Patented Nov. 15, 1960 1 2 to addition reactions with alkali metals and, hence, such 2,960,544 benzenes have been considered for and used as inert carrier mediums for preparing ?nely divided dispersions PROCESS FOR PREPARING DI-ALKALI METAL AROMATIC HYDROCAR'BONS AND PRODUCTS of the alkali metals for use in reaction for adding sodium THEREFROM to condensed ring systems. Substitution reactions are known wherein an aliphatic derivative of an alkali metal, Irving L. Mador and Theodore S. Soddy, Cincinnati, such as amylsodium or amylpotassium will metalate Ohio, assignors to National Distillers and Chemical benzene to replace a hydrogen atom to produce phenyl ‘Corporation, New York, N.Y., a corporation of Vir ginia sodium or phenylpotassium 'or disodio- or dipotassioben 10 zene, but in such substitution reactions the aromatic con No Drawing. Filed May 12, 1958, Ser. No. 734,390 jugation is left intact and dihydro derivatives are not formed. Thus, in the case of toluene, the substitution 12 Claims. (Cl. 260-665) reaction with amylsodium takes place on the alkyl group initially so that benzylmetal compounds are formed. This invention relates broadly to a process for prepara 15 Moreo"er, it is also known that benzene may be reduced liOn of alkali metal adducts of certain aromatic hydro to dihydrobenzene by reaction with sodium and an alco carbons and, more particularly, to a method for preparing hol in liquid ammonia but, in such a reaction, the alcohol alkali metal derivatives, such as potassium derivatives, is essential for reaction with the sodium whereby to pro of benzene and alkyl-substituted benzenes. duce hydrogen that undergoes addition to the benzene. It is an object of this invention to provide a method 20 In the present process, the desired adduct formation carried out under selected reaction conditions whereby is effected by reacting benzene, or an alkyl—substituted an alkali metal is added to benzene and alkyl-substituted benzene with certain alkali metals in certain reaction benzenes to provide the corresponding metallo deriva media at a temperature of below about —10° C. and, tive of dihydrobenzene and alkyl-substituted dihydro preferably, substantially below —10° C. For use in such benzenes and which metal adducts can be subjected to 25 a reaction and, in addition to benzene itself, homologs further reactions to produce highly valuable and useful thereof such as alkyl-substituted benzenes in which the derivatives. alkyl-substituent contains from one to six carbon atoms It is a further object of this invention to provide a may be used with speci?c examples being toluene, the process for preparation of alkali metal adducts of ben xylenes, ethylbenzene, durene, etc. zene and alkyl-substituted benzenes, in which the de 30 Although temperatures of below about —10° C. may sired adduct-forming reaction is effected rapidly and to be used, substantially lower temperatures are preferred, a substantial extent. such as below about -—20° C. and even substantially Still another object of this invention is the provision lower as the still lower temperatures are more favorable of a method for preparation of alkali metal adducts of to the desired reaction. Thus, temperature as low as dihydrobenzene and alkyl-substituted dihydrobenzenes, —100° C. are particularly suitable with a highly satis and conversion thereof to salts of dihydroaromatic di factory range being from about —20" C. to about carboxylic acids, followed by liberation of the free acids ~75° C. from their salts with a speci?c object being the ultimate The alkali metal employed is preferably potassium production of terephthalic acid and cyclohexanediacids 40 although other alkali metals such as rubidium and cesium by dehydrogenation or hydrogenation reactions, respec may be used. Thus, suitable for practice are alkali tively. metals such as potassium, rubidium, cesium and alloys A still further object is the preparation of glycols by of such metals with sodium, and the like. a method starting with reaction of an alkali metal with The alkali metal can be used in a variety of forms. benzene and alkyl-substituted benzenes to prepare alkali 45 Thus, it may be used in ?nely dispersed form or as large metal adducts of dihydrobenzene and of alkyl-substituted pieces with the ?nely dispersed form being preferred as dihydrobenzenes and conversion thereof, by reaction with it expedites the desired reaction. When use is made of epoxy compounds, to glycols. the alkali metal as a ?nely divided suspension, it can be A further object is to provide a method for prepara suspended in a variety of inert media such as, for ex tion of alkali metal adducts of benzene and alkyl-sub ample, in isooctane, n-octane, kerosenes, mineral spirits, stituted benzenes which undergo Grignard reactions with paraf?ns, other saturated para?inic hydrocarbons, etc. Grignard type reactants to provide highly valuable and Certain ethers may also be used as dispersion media pro useful derivatives. vided they are not susceptible to extensive cleavage by The present invention is based on the discovery that the alkali metal, suitable examples thereof being ethers certain alkali metal adducts of dihydrobenzene and alkyl 55 such as butyl ether and 1,2-dimethoxyethane, and others. substituted dihydrobenzene can be prepared by reaction Moreover, for the dispersing medium, use may also be of an alkali metal with benzene or alkyl-substituted made of the benzene or alkyl-substituted benzene of benzene under de?ned conditions of temperature and which the adduct formation, as is embodied herein, is certain reaction mediums whereby an alkali metal adds desired. Thus, in carrying out the reaction embodied to the double bond’ system of benzene and alkyl-sub herein to form the adduct of benzene or alkyl-substituted stituted benzenes. That benzene and alkyl-substituted benzene, the alkali metal can be dispersed in benzene or benzenes can be effectively reacted to provide such a re an alkyl-substituted benzene and the resulting dispersion cult is clearly novel and unexpected as is apparent from added to the reaction medium at the temperature condi the following remarks. tions effective for forming the alkali metal adduct. It is known that, under certain selected reaction con 65 The reaction media most suitable for the process em ditions, alkali metals will add to condensed ring systems bodied herein comprise certain types of ethers and ter such as naphthalene, anthracene, etc. to produce alkali tiary amines which also promote the alkali metal addi metal adducts and that alkali metals will add to non tion reaction. Such ethers include aliphatic mono ethers condensed polyaryls such as terphenyls, quaterphenyls, in which the ratio of the number of oxygen atoms to the etc. However insofar as we are aware, the simple ring 70 number of carbon atoms is not less than 1:4, and which systems such as benzene, toluene, the xylenes, ethyl will not be cleaved during the reaction period to produce benzenes and related members have been considered inert cleavage products which may consume appreciable 2,900,544 3 '4 amounts of the reaction products or function as nega substituted dihydrobenzenes prepared in accordance with tive catalysts. Examples include cyclic ethers such as this invention may be isolated as such but preferably, tetrahydrofuran and dioxane and ethers containing a they are directly and immediately upon preparation sub methoxy group such as dimethyl ether, methyl ethyl jected to further reactions to form valuable derivatives. ether, methyl n-propyl ether, methyl isopropyl ether, and 6 For example, subsequent carbonation of the reaction mix mixtures of these ethers. Certain aliphatic polyethers are ture containing the products yields the salts of dihydro also quite satisfactory. These include polyethers which aromatic dicarboxylic acids which, in the case of benzene, are derived by replacing all of the hydroxyl hydrogen is the dialkali metal salt of 1,4-dihydroterephthalic acid. atoms of the appropriate polyhydric alcohol by alkyl The carbonation may be carried out by subjecting the groups. Typical examples are the ethylene glycol dialkyl 10 adducts to contact with dry gaseous carbon dioxide, with ethers such as the dimethyl, methyl ethyl, diethyl, methyl solid carbon dioxide or by adding the adducts to a solu butyl, ethyl butyl, dibutyl, and butyl lauryl ethylene tion of CO2 in an inert liquid. The temperature of car glycol ethers; trimethylene glycol dimethyl ether, glycerol bonation should be held below —l0° C. to avoid decom trimethyl ether, and glycerol dimethyl ethyl ether. Ma position and formation of undesirable by-products. The terials such as N-methylmorpholine, trimethylamine and 15 salts obtained from such carbonation of the adducts will the like also may be used. The simple methyl mono contain two more carbon atoms per molecule than the ethers, as dimethyl ether, and the polyethers of ethylene dialkali metal derivative of the dihydroaromatic com glycols, such as ethylene glycol dimethyl ether, are pre pound from which they are produced. In the case where ferred. benzene and potassium/are the starting reactants, there The ethers should not contain any groups such as 20 results by this method the selective production of 1,4 hydroxyl, carboxyl and the like which are distinctly re dipotassio-2,5-cyclohexadiene. Acidi?cation and dehy active towards alkali metal. Although the ether may drogenation of this material following carbonation re react in some reversible manner, it must not be subject to sults in production of terephthalic acid. It is also pos cleavage to give irreversible reaction products during the & sible to hydrogenate the l,4-dicarboxy-2,S-cyclohexadiene addition reaction as such cleavage action destroys the 25 ‘to obtain 1,4-dicarboxylcyclohexane. These acids are ether and introduces into the reacting system metallic useful in preparation of polyesters, polyurethanes, poly alkoxides which, in turn, tend to prevent the addition meric plasticizers and synthetic polymers. reaction from taking place or destroy the addition prod The adducts of benzene and alkyl-substituted benzenes uct once formed. produced by the method herein may also be reacted with Inert liquids can be employed in limited amounts in 3'0 epoxides, such as ethylene oxide, to produce glycols with mixture with the aforesaid reaction media. In general, a speci?c example thereof being bis-l,4-(2'-hydroxy such inert liquids are introduced with the alkali metals ethyD-dihydrobenzene which, for example, can be hy~ and especially so when the alkali metal is used as a drogenated and/or dehydrogenated to provide products suspension. Moreover, the reaction mixture should be useful in the preparation of polyesters, polyurethanes free of impurities such as water, alcohols, unsaturated 35 and the like. compounds or other materials which would react with The adducts of benzene and alkyl-substituted benzenes either the alkali metal reactant or the adducts formed produced by the process of this invention may be further in the reaction to produce by-products which would in utilized in the preparation of diamines by reaction with terfere with or prevent the desired addition reaction from a haloamine, such as chloramine, to prepare diamines taking place. 40 useful as the amine component in the preparation of In carrying out the invention embodied herein, reac highly useful polyamides. tion between the alkali metal and benzene or an alkyl In addition to carbonation, the adducts of benzene and substituted benzene is substantially instantaneous, but, alkyl-substituted benzenes may be reacted with any of to insure substantial completion of reaction, a period many other Grignard type reactants having carbonyl, of from about one-half to about four hours is normally 45 thionyl, nitrile and halogen groups to form highly valu allowed. 'However, factors such as temperature, alkali able products. Typical examples of such Grignard type metal particle size and rate of agitation may necessitate reactants are oxygen, formaldehyde, acetaldehyde, ace variations in the time allowed for substantial completion tone, acetonitrile, propionitrile, sulfur, sulfur dioxide, sul of the reaction. Thus, whereas use of 1-2 micron par fur trioxide, thionyl chloride, chloromethyl ether, di ticle size average dispersion may react substantially com 50 methyl sulfate, methyl chloride, ethyl chloride, chlorine pletely in about one-half hour or less at a temperature and the like. Thus, the alkali metal adduct of benzene of —75° C., use of substantially larger particles, e.g., one can be reacted in typical Grignard type reactions with quarter inch pellets of an alkali metal may require a sulfur to produce a dimercaptan, with sulfur dioxide to substantially longer time, e.g., four or more hours and a disul?nic acid, with formaldehyde to a diol, with in some cases up to twenty-four hours for substantial 65 cyanogen chloride to a dinitrile, or the adducts may be completion of reaction. used generally as Grignard type reactants to provide ad The reaction may be carried out in either batch-wise, dition reactions with esters, anhydrides and nitriles. Still semi-continuous or in a continuous fashion. further, cyanogen and cyanogen chloride are suitable for The desired reaction can be carried out using the re reaction with the alkali metal adducts of benzene and actant in substantially stoichiometric amounts or, either 60 alkyl-substituted benzenes to provide highly useful de of the reactants in excess. Thus, when it is desired to rivatives thereof. substantially completely react the alkali metal, it is used The adducts produced by the method embodied herein in substantially stoichiometric or less amount. On the by reaction of the alkali metal with benzene or an alkyl other 'hand when it is desired to substantially com substituted benzene may be used per se, or in combination pletely react the benzene reactant, the alkali metal is 65 with other catalysts, as polymerization catalysts for a used in excess, as for example, in excess of 2 and up variety of ole?ns such as ethylene, styrene, butadiene and to about 2.2 g. atoms of alkali metal to one mole of similar materials. the benzene or alkyl-substituted benzene. , In order to further describe the invention, several em However, the preferred aspect of this invention in~ bodiments thereof are set forth hereinafter for purposes volves the use of an excess of the aromatic compound 70 of illustration and not limitation. over the theoretical quantity required to form the di alkali metal derivative, e.g., use of a ratio of 2 gram Example 1 atoms of the alkali metal to from more than one and up A 0.37 g. atom portion of ?nely dispersed potassium to about 8 moles of the aromatic compound. metal (particle size 1 to 38 microns, stabilized with 0.5% The alkali metal adducts of dihydrobenzene and alkyl 75 aluminum stearate) in 40 m1. of alkylate and 200 ml. of 2,960,544 5 anhydrous 1,2-dimethoxyethane were introduced into a carbonation was effected by passing carbon dioxide over round-bottomed ?ask. The suspension was cooled to the surface of the reaction mixture for 35 minutes. By —72° C. and stirred for 1 hour whereupon a solution of hydrolysis of the reaction mixture, separation of the re 0.6 mole of benzene in 60 ml. of 1,2-dimethoxyethane sulting basic layer, and acidi?cation to a pH of 1 with was added. The reaction mixture was stirred at --76° C. concentrated hydrochloric acid, 1,4-dicarboxy-2,5-cyclo for 3 hours, and then carbonated by passing carbon di hexadiene was obtained. oxide over its surface for 2 hours. The resulting carbo Example 5 nated mixture, when warmed to 0° C., was hydrolyzed with 50 m1. of a 1:3 water-dimethoxyethane mixture and, Into a 1000 ml. ?ask was introduced 5.7 g. (0.22 g. ?nally, was diluted with 100 ml. of water. The basic 10 atom) of a potassium-sodium dispersion (1:4) and 100 layer was washed with diethyl ether to produce a yellow ml. of dimethoxyethane. on cooling this suspension to brown product which, on acidi?cation with hydrochloric —70° C., a blue color was formed. To this mixture acid produced 10.5 g. of crude 1,4-dicarboxy-2,5-cyclo was added dropwise 7.8 g. (0.1 mole) of benzene in 50 hexadiene (M.P.>270° C.) in a yield of 54% based on ml. of dimethoxyethane over a 30 minute period where the amount of potassium employed: 15 by a yellow complex salt was formed. After the yellow Upon analysis, the acid thus obtained gave the follow complex salt intermediate had precipitated, the reaction ing values: mixture was carbonated on solid carbon dioxide. After hydrolysis of the carbonation mixture, the basic extract 1,4-dlcarboxy-2,5-cyclohexadiene was acidi?ed to a pH of 1 whereupon 1,4-dicarboxy-2,5 20 cyclohexadiene was obtained. Found Calculated Example 6 f0r(CsHsO4) Into a 1000 ml. ?ask was introduced 8.6 g. (0.22 g. Iodine No 2021 b 167 2381.47 atom) of a potassium dispersion in 200 ml. of dimeth 0mm _Hydmgen ------\Hydrogen—4.83o%___I ar on—57. .____ 4.76%.0_ . oxyethane. In cooling the suspension to —70° C., a Neutralization Equivalent ______.. 86.5 ______-_ 84. blue color was noted. Four grams (0.05 mole) of ben zene was added dropwise in 50 ml. of dimethoxyethane. Example 2 The color turned green, and 1,4-dipotassio-2,S-cyclohexa diene separated. Ethylene oxide (35.2 g., 0.8 mole) A 0.44 g. atom portion of ?nely dispersed potassium 30 was passed over the reaction mixture by entrainment metal in 70 ml. of mineral spirits and 100 ml. of anhy with argon. Red-brown and dark red color sequences drous 1,2-dimethoxyethane were introduced into a round were observed. The reaction mixture was hydrolyzed, bottomed ?ask and cooled to —70° C. At the end of 1 and the ether layer separated and combined with two di hour, 15.6 g. (0.2 mole) of benzene in 50 ml. of dimeth ethyl ether extracts (50 ml. each) of the water layer. oxyethane was added over a period of 20 minutes. The The combined organic extracts were dried over anhy reaction mixture was then stirred at —75 ° C. for 2 hours, drous magnesium sulfate. The dried ether extract was and carbonated by passing carbon dioxide gas over the concentrated, and the residue distilled to yield a yellow surface of the reaction mixture for 1 hour. oil (B.P. 150-155” C. at 1 to 0.1 mm.), i.e., bis-1,4-(2’ The mixture was then hydrolyzed by adding dropwise hydroxyethyl)-2,5-cyclohexadiene which analyzed as fol a 50 ml. solution of 1:4 water-dimethoxyethane mixture, 40 lows: a 1:2 water-dimethoxyethane mixture, and, ?nally, 100 Calc. for CIOHIQOQ; C, 70.43; H, 9.52. Found: C, ml. of water. The basic extract was separated, treated 69.87; H, 9.28. with charcoal and ?ltered. On acidi?cation of this extract with concentrated hydrochloric acid to a pH of 1, crude Example 7 1,4-dicarboxy-2,S-cyclohexadiene was obtained as a white Into a small ?ask was placed 5 g. of 1,4-dicarboxy amorphous powder in a yield of 18 g. (54% based on 45 2,5-cyclohexadiene and 1.2 g. of sulfur. This mixture benzene) which darkened on heating over 270*’, but did was heated to 250-275° C. for 1 hour. The odor of not melt. hydrogen sul?de was quite distinct. The residue which The acid was esteri?ed by a conventional esteri?cation remained on cooling the ?ask was extracted with caustic; reaction with phosphorous pentachloride and methanol, treated with charcoal, and ?ltered. The ?ltrate was acidi such esteri?cation being accomplished with simultaneous 50 ?ed to yield 2.5 g. (50%) of terephthalic acid. dehydrogenation to produce the dimethyl ester of terephthalic acid which melted at 144-145 ° C. (140 Example 8 141° C. corr’n.), i.e., the literature value for the methyl Into a dried, nitrogen-?ushed gas bottle was introduced ester of terephthalic acid. ‘A mixed melting point of the 55 20 ml. of reduced platinum on carbon and 5.1 g. (0.03 ‘ ester thus produced with a known sample of the dimethyl mole) of 1,4—dicarboxy-2,5-cyclohexadiene which was dis ester of terephthalic acid showed no depression and the solved in 50 ml. of 10% sodium hydroxide. This mix infrared spectra of both samples were identical. ture was attached to a rocking hydrogenation apparatus Example 3 for 15 hours at 48 p.s.i.g. of hydrogen. The ?ltered 60 solution was acidi?ed and the crude acid crystallized A potassium dispersion was prepared from 14 g. of from water to give 2.5 g. of 1,4-dicarboxycyclohexane potassium in a bal?ed ?ask by high speed stirring in a melting at 160—161° C. suspending media of mineral spirits (125 ml.) and di methoxyethane (125 ml.). The dispersion was cooled to Example 9 —70° C., 50 ml. of anhydrous benzene was added, and the mixture stirred at —74° C. for one hour. The re 65 A mixture of 2 g. of a potassium dispersion in mineral action mixture was then carbonated with carbon dioxide spirits and 20 mls. of dimethyl ether under an argon at- ' and hydrolyzed in the manner described in Example 1 mosphere was cooled to —75° C. and a yellow-brown whereby there was produced 1,4-dicarboxy-2,5-cyclo color developed. Upon addition of benzene, the surface hexadiene in a 34% yield based on the potassium used. of the metal turned yellow as in Example 5 showing the 70 formation of the potassium-benzene adduct. Example 4 While there are above disclosed but a limited number To a mixture of 16.2 g. of sodium-potassium (1:4) of embodiments of the process of the invention herein alloy and 250 ml. of anhydrous dimethoxyethane was presented, it is possible to produce still other embodi added 50 ml. of anhydrous benzene at -—100° C. The ments without departing from the inventive concept here reaction mixture was permitted to rise to —78° C. and 75 in disclosed, and it is desired therefore that only such 2,980,544 7 . limitations be imposed on the appended claims as are 7. A process, as de?ned in claim 1, wherein the alkali stated therein. 1 metal is ?nely divided. What is claimed is: 8. A process, as de?ned in claim 1, wherein the reac 1. A process which comprises reacting an alkali metal tion mixture comprising the alkali metal adduct of the from the group consisting of potassium, rubidium and aromatic hydrocarbon is reacted with a Grignard reactant. cesium with an aromatic hydrocarbon from the group 9. A process which comprises reacting benzene with consisting of benzene and alkyl-substituted benzenes at potassium at below about -10° C. in a reaction medium below about —-10° C. in an inert liquid reaction medium comprising 1,2-dimethoxyethane to form a potassium ad to form the alkali metal adduct of said aromatic hydro~ duct of benzene. carbon. - 10 10. A di-alkali metal addition product of benzene. 2. A process, as de?ned in claim 1, wherein the alkali 11. A dipotassio adduct of benzene. metal is potassium. 12. l,4-dipotassio-2,S-cyclohexadiene. 3. A process, as de?ned in claim 1, wherein the aro matic hydrocarbon is benzene. . References Cited in the ?le of this patent 4. A process, as de?ned in claim 1, wherein the reac 15 UNITED STATES PATENTS tion medium is an ether from the group consisting of 2,019,832 Scott ______.. Nov. 5, 1935 aliphatic monoethers having an oxygen to carbon ratio 2,548,803 Little ______- Apr. 10, 1951 of not less than 1:4 and polyethers derived from an ali r 2,750,411 Fisher et a1. ______June 12, 1956 phatic polyhydric alcohol having all hydroxyl hydrogen 2,765,334 Stinson et al. ______Oct. 2, 1956 atoms replaced by alkyl groups, and mixtures of said 20 2,788,377 Barber ______._ Apr. 9, 1957 ethers. 2,795,624 Nobis et al. ______- June 11, 1957 5. A process, as de?ned in claim 1, wherein the reac 2,812,363 Mills ______.._ Nov. 5, 1957 tion medium is 1,2-dimethoxyethane. 2,816,935 Watson et al. ______Dec. 17, 1957 6. A process, as de?ned in claim 1, wherein the reac 2,823,238 Beets et al. ______Feb. 11, 1958 tion is carried out at from about -20° C. to about 25 2,852,568 Schmerling ______Sept. 16, 1958 —75° C. 2,868,842 Closson et al. ..___' ______Jan. 13, 1959