Preparations of benzoquinone and derivatives thereof
United States Patent [1 1 Costain et al.  
 [ Apr. 29, 1975 PREPARATIONS OF BENZOQUINONE AND DERIVATIVES THEREOF [75] Inventors: Winston Costain; Bernard William Hugh Terry, both of Manchester, England [73] Assignee: Imperial Chemical Industries Limited, London England [22] Filed: Mar. 23, 1971 [21] Appl. No.1 127,406  
 [30] Foreign Application Priority Data Apr. 22. l97() United Kingdom 19287/70 [52] U.S. Cl 260/396 R [51] Int. Cl. C07c 49/64 [58] Field of Search 260/575, 580, 396 R [56] References Cited UNITED STATES PATENTS 2.295.446 9/1942 Behnisch 260/396 2.480.071 8/1949 Ziegler 260/396 Primary ExaminerVivian Garner Attorney, Agent, or FirmCushman, Darby &amp; Cushman [5 7] ABSTRACT 6 Claims, No Drawings PREPARATIONS ()F BENZOQLTINONE AND DERIVATIVES THEREOF This invention relates to a process for the manufacture of benzoquinone compounds.  
  Benzoquinone is manufactured commercially by the oxidation of aniline with manganese dioxide or with sodium dichromate and sulphuric acid. The manganese dioxide process requires long reaction times at temperatures less than 10C and forms considerable quantities of manganese sulphate as an unwanted byproduct. It is however the more commonly used process, oxidation of aniline with sodium dichromate and sulphuric acid, also at temperatures less than 10C. having hitherto been considered to be a less satisfactory process giving poorer yields. This latter process is described in the literature as.a process in which dichromate is added in two distinct stages with very long reaction times of the order of 24-36 hours and operated in this way it gives yields of the order of 50607(. Thus R. O. C. Norman in Principles of Organic Synthesis (Methuen &amp; Co. Ltd. 1968) at page 509 records that &#34;aniline is oxidised to p-benzoquinone in 60% yield by dichromate&#34;.  
  lt has now been found that, contrary to all teaching on the subject, improved yield of benzoquinone can be obtained by operating this latter process for short periods and that the temperature employed may be very much higher than 10C provided that the operating time is sufficiently short.  
  According to the invention therefore a process for the manufacture of benzoquinone or a nuclearly substituted benzoquinone comprises uninterruptedly bringing together and mixing aniline or an oor msubstituted aniline with chromic acid in sulphuric acid medium in a reaction zone at to 100C and keeping these substances in the reaction zone for a total time effective to produce benzoquinone but not exceeding minutes, the relationship between and the temperature y in C being according to the equation provided that in no case does exceed 360.  
  In the process of the invention optimum yields of benzoquinone may be obtained while using smaller proportions of chromic acid than are used in prior art processes. Advantageously from 0.65 to 0.9 and more particularly from 0.7 to 0.8 moles of chromic acid per mole of aniline or substituted aniline may be used. Even lower proportions of chromic acid may be used, if lower yields of benzoquinone are acceptable. As in prior art processes however, the proportion of chromic acid may be increased if desired, proportions up to 2 molar per mole of aniline having no marked adverse effect on the yield of benzoquinone.  
  0- or m-substituted anilines which may be oxidised by the process of the invention include o-methylaniline. o-ethylaniline, and higher o-alkyl and o-aryl anilines, o-haloanilines, o-nitro aniline. m-methyl aniline and higher m-alkyl and aryl anilines, m-halo anilines, mnitro aniline and o-/m-polysubstituted anilines.  
  The strength of the sulphuric acid used is not a critical feature of the process of the invention. Acid of N to N strength can be used to produce benzoquinone compounds in high yield. For economic reasons, however, and for avoidance of hazards it is desirable to avoid using sulphuric acid of greater than lON strength, and generally acid of 3N to lON strength is preferred.  
  The concentration of the aniline or substituted aniline in the sulphuric acid may be for example between 0.1% and 7% by weight preferably 0.5 to 4.0% by weight depending on the acid strength used.  
  Preferred temperatures are from 10 to 40C ordinary atmospheric temperatures being satisfactory. The oxidation is not so exothermic as to cause difficulty in controlling the temperature. ,Within the stated limits strict temperature control is not of great importance so long as the residence time is adjusted accordingly.  
  Bringing together and mixing of the reactants can therefore be effected quite rapidly. At the higher temperatures ofthe range total residence times are so short that in practice they may substantially correspond to the minimum amount of time required to bring together and mix the reactants, i.e. the aniline and chromic acid, with each other. Even at lower temperatures benzoquinone formation is substantially complete in a much shorter time than those used in prior art processes, but subject to the above-stated limits the yields of benzoquinone at low temperatures is not substantially decreased by keeping the mixture in the reaction zone after mixing is complete. For economic reasons however it is preferred not to exceed an overall residence time of 360 minutes.  
  An essential feature of the process is that the reactants should be brought together and mixed without substantial interruption. Conveniently solutions of the aniline in sulphuric acid and of ammonium, sodium or potassium dichromate or chromium trioxide in sulphuric acid may be prepared and the one added to and mixed with the other uninterruptedly.  
  As desired the process may be operated batchwise or continuously. In either case it is preferred to bring together and mix the reactants in such a way that, during substantially the whole of the period of time occupied thereby, unoxidised or incompletely oxidised aniline or substituted aniline is present in the reaction zone. Thus for batchwise operation it is preferred to add chromic acid to the aniline or substituted aniline in sulphuric acid medium. Reverse operation i.e. by adding the aniline in sulphuric acid medium to chromic acid gives lower, but still practicable yields of benzoquinone compounds. Likewise for continuous operation it is preferred to feed the aniline or substituted aniline solution into the reaction zone in advance of the chromic acid.  
  The benzoquinone compound may be isolated in known manner from the mixture produced by the process of the invention, for example by steam distillation and/or by solvent extraction. Suitable solvents include chloroform, methyl chloroform, methylene chloride, ethylene dichloride, 1,2,2-trichloroethylene, diethyl ether, hexane or other normal or iso-paraffins, cyclohexane, methyl cyclohexane, toluene, benzene or nitrobenzene. If desired butadiene (under slight pressure) can be used for the extraction, thus producing a solution which is directly useful for submission to a Diels- Alder reaction as a step in the production of anthraquinone or naphthaquinone.  
  After removal of the benzoquinones the spent acid may be electrolytically oxidised to regenerate chromic acid.  
  If desired, solvent may be present during the process of the invention, thus reducing the amount of contact between the product benzoquinone compounds and the chromic acid and thereby lessening the extent to which the desired product is decomposed by further oxidation.  
  Wetting agents, for example, quaternary ammonium salts, such as cetyl trimethyl ammonium bromide. and higher alkyl or alkenyl sulphonic acid salts. may be present during the process of the invention or during a subsequent solvent extraction if desired.  
  The process is economically attractive compared with prior art procedures. reaction times being only a fraction of those previously used. Other advantages are reduced chromic acid requirement, much less critical temperature control and considerably higher yields. with consequent lower production of unwanted byproducts and simplification of purification procedures.  
  The aniline or substituted aniline used as starting material in the process of the invention may be in admixture with a p-aminophenol which, as is already known, can be oxidised to a benzoquinone by means of chromic acid in sulphuric acid.  
  According to a further feature of the invention therefore a process for manufacture of benzoquinone or a substituted benzoquinone comprises reducing nitrobenzene or an or m-substituted nitrobenzene in known manner to produce a mixture of a paminophenol and an aniline and uninterruptedly bringing together said mixture with chromic acid in sulphuric acid under the conditions previously described.  
  Mixtures of a p-aminophenol and an aniline may be produced for example by catalytic hydrogenation of a nitrobenzene in presence of sulphuric acid using a platinium-on-carbon catalyst.  
  Benzoquinone manufactured by the process of the invention may be used as an intermediate for the production of other chemicals. Thus:  
  Naphthaquinone, an intermediate in the dyestuffs industry. may be produced in known manner by reaction of the benzoquinone with one molar proportion of butadiene, followed by oxidation of the resultant tetrahydronaphthaquinone.  
  Anthraquinone. an intermediate in the dyestuffs industry, may be produced in known manner by reaction of the benzoquinone with two molar proportions of butadiene, followed by oxidation of the resultant octahydroanthraquinone.  
  1,4-Cyclohexanediol, an intermediate useful to the production of polymers, for example polyesters. and  
 plasticisers, may be produced in known manner by catalytic hydrogenationof the benzoquinone. using for example a Raney nickel or Raney cobalt catalyst.  
 Hydroquinone, useful in photography may be produced in known manner by reduction of the benzoqui- Example 1 12 parts of sodium dichromate dihydrate dissolved in 50 parts of 4N sulphuric acid were added uniformly during 18 minutes to an agitated solution of 4.65 parts of aniline in 250 parts 4N sulphuric acid, the temperature being maintained at 25 i 1C throughout the addition. Stirring was continued for 1 minute with the temperature held at 25 i 1C and the resulting solution was extracted with 5 X 100 parts of methylene chloride and an aliquot estimated iodemetrically. The benzoquinone yield was 85.3% of theoretical on the aniline added. The isolated and recrystallised benzoquinone had a m.p. and mixed m.p. of 116-7C.  
 Examples 2-27 In each of these Examples 4.65 parts of aniline were oxidised to benzoquinone in the manner generally described in Example 1, with the quantities of sodium dichromate and sulphuric acid, and the normality of the sulphuric acid, the temperature and the times of addition and holding varied as indicated in the following table. The yield of benzoquinone are indicated in the last column.  
  Examples 2, 6, 8 and 26 were carried out in presence of 150 ml of methylene dichloride.  
  Example 4 was carried out by simultaneous addition of the dichromate and aniline to the acid, in presence of 150 ml of methylene dichloride.  
  In Example 5 the aniline in 150 ml of methylene chloride was added to the dichromate in sulphuric acid.  
  In Examples 7, 20 and 22 the sulphuric acid was equally distributed between the aniline and the dichromate.  
  SULPHURIC ACID Addition Holding Example Na Cr. ,O 2H O parts Normality Temp. Time Time 71 yield of parts by vol. in C in Min. in Min. bcnzoquinonc 2 300 4 -25 31 l 82.9 3 15 300 4 20-25 30 1 82.1 4 I5 300 4 20-25 33 8 76.0 5 15 300 4 23-25 31.5 1 57.5 6 15 300 4 38-39 30 1 83.5 7 I2 300 7 24 24 1 92.6 8 12 300 4 20 50 1 90 9 12 150 7 19 1 84.0 l0 I2 450 2 25 l 78.2 1 1 I2 200 10 25 6 l 80.7 12 1 l 300 5 23 31 1 85.4 13 10 300 5 25 31 1 79.0 14 9 300 5 25 28 I 60.6 l5 12 300 4 8-12 1 l O 74.0 l6 I2 300 4 8-12 11 300 76.8 l7 12 300 4 54 5.5 1 62.9 18 12 300 4 78-80 0.5 0 60.5 19 12 300 4 77 21 1 14.5 20 I2 300 I0 24 24 1 91.9 21 12 450 4 30 1 90.5 22 12 300 4 20 23 1 88.6 23 I2 300 4 100 0.5 I 46.1 24 I2 300 4 I I 54.4 25 12 300 5 23- 5 32 1 85.0 26 15 300 4 6-8 46 4 83.7 27 12 350 4 10 176.5 0 85.9  
 Example 28 Example 1 was repeated using 5.35 parts of otoluidine in place of the aniline and adding the dichromate in sulphuric acid during 29 minutes at 25C. An 81.1% yield of toluquinone. m.p. 66.568.5C was obtained.  
 Example 29 Example 25 was repeated using 5.35 parts of mtoluidine and 4N sulphuric acid. A 59.7% yield of toluquinone was obtained. m.p. 68-69.5C.  
 Example 30 Example 25 was repeated using 6.35 parts of ochloroaniline and 4N sulphuric acid with the dichromate/sulphuric acid mixture added during 36 minutes at 23-25C. A 17.2% yield of chlorobenzoquinone. m.p. 5760C. was obtained.  
 Example 31 Nitrobenzene (12.3 parts). 59; platinum-on-carbon catalyst (0.2076 part). cetyl trimethylammonium bromide (0.05 part) and 4N sulphuric acid (400 parts by volume) were heated to 85 i 1C and maintained at this temperature during reaction. at atmospheric pressure. with hydrogen. Absorption started immediately the system was agitated and averaged 71 parts by vol.- lminute during the 80 minute reaction time. The agitation was then stopped. the system cooled and the hydrogen atmosphere replaced with nitrogen. Analysis of the reaction mixture. after filtering free from catalyst. showed it to contain p-aminophenol (7.42 parts) and aniline (298 parts).  
  Half of the catalyst-free reaction mixture was oxidised directly with sodium dichromate dihydrate (7.0 parts) in 4N sulphuric acid (25 parts by vol.) at 5-l0C during seventy minutes and the resultant benzoquinone was extracted with methylene chloride. 4.09 parts of benzoquinone were produced. The benzoquinone yield was therefore 75.67r. which is about 10% greater than the theoretical yield from the paminophenol present.  
 We claim:  
  1. A process for the manufacture of benzoquinone or an alkyl or halogenobenzoquinone which comprises uninterruptedly bringing together and mixing aniline or a monosubstituted oor m-alkyl or halogenoaniline with from 0.65 to 2.0 molar proportions of chromic acid in sulphuric acid medium ofN to N strength, the concentration of aniline or alkyl or halogenoaniline in the sulphuric acid being from 0.1% to 7% by weight. in a reaction zone at 0 to 100 C and keeping the mixed substance in the reaction zone for a total time effective to produce benzoquinone or an alkyl or halogenobenprovided that for temperatures (y) which according to said equation would be related to a maximum residence time (x) in excess of 360. the maximum residence time in no case exceeds 360 minutes.  
  2. Process according to claim 1 operated at 10 to 40C.  
  3. Process according to claim 1 operated by bringing together and mixing the aniline or alkyl or halogenoaniline with the chromic acid in such a way that. during substantially the whole of the period of time occupied thereby. unoxidised or incompletely oxidised aniline or alkyl or halogenoaniline is present in the reaction zone.  
  4. Process according to claim 3 operated batchwise by adding chromic acid to the aniline or substituted aniline in sulphuric acid.  
  5. Process according to claim 3 operated continuously by feeding aniline or substituted aniline solution into the reaction zone in advance of the chromic acid to maintain unoxidised or incompletely oxidised aniline or substituted aniline in said zone.  
  6. Process for the manufacture of benzoquinone or an alkyl or halogenobenzoquinone which comprises catalytically hydrogenating nitrobenzene or a monosubstituted oor m-substituted nitrobenzene in the presence of sulphuric acid to produce a mixture of a paminophenol and an aniline. uninterruptedly bringing together and mixing the resultant mixture with from 0.65 to 2.0 molar proportions of chromic acid in sulphuric acid medium of 3N to ION strength. the concentration of aniline or alkyl or halogenoaniline in the sulphuric acid being from 0.1% to 7% by weight, in a reaction zone at0 to C and keeping the mixed substances in the reaction zone for a total time effective to produce benzoquinone or an alkyl or halogenobenzoquinone but not exceeding .r minutes, the relationship between x and the temperature y in C being according to the equation provided that for temperatures (y) which according to said equation would be related to a maximum residence time (.r) in excess of 360. the maximum residence time in no case exceeds 360 minutes.