2,899,465 atent 1C6 Patented Aug. ll, 1959

1 2 manner is oxidized by nitric acid and it is_'believed that 2,899,465 this reaction proceeds as follows: TRICHLOROBENZENE COMPOUNDS AND THEIR PRODUCTION Theodore A. Girard, Wayne Township, Passaic County, and David X. Klein, Upper Montclair, N.J., assignors 01 to Heyden Newport Chemical Corporation, a corpora tion of Delaware 00011 10 No Drawing. Application March 21, 1955 01 01 ’ ‘ Serial No. 495,781 + H1803 + 4HNO1 +501 6 Claims. (Cl. 260-523) C1 In accordance with the last mentioned reaction each mole The present invention relates to the production of tri 15 of the thiosulfuric acid compound requires 4 moles of chlorobenzoic acid and is primarily concerned with the nitric. acid. However, if the trichlorobenzyl thiosulfuric production of 2,3,6-trichlorobenzoic by the oxidation with acid is formed in situ'from' the trichlorobenzyl sodium nitric acid of one of the novel compounds, 2,3,6-tri thiosulfate, then the stoichiometric amount of nitric acid lchlorobenzylamine, 2,3,6-trichlorobenzyl sodium thio is 5 moles per mole of starting material. The foregoing sulfate, 2,3,6-trichlorobenzyl thiosulfuric acid or di(2,3,6 20 description refers to sodium thiosulfate and it is to be trichlorobenzyl) sul?de. understood that other alkali'metal thiosulfates may be Benzylehloride having either no nuclear chlorination used in the same manner. or nuclear monochlorination can be oxidized With potas The sul?de'can be readily prepared by reacting 2,3,6. sium permanganate to the corresponding benzoic acid. trichlorobenzyl chloride with alkali metal sul?de. This Dilute nitric acid can be used to oxidize benzylchloride 25 reaction may be represented by the‘following equation: to benzoic acid but concentrated nitric acid tends to eifect nuclear nitration. Trichlorobenzyl compounds enter into OHgCl CH2 . S-————CH2 reactions involving the benzyl side chain with relatively great dif?culty and this is especially true of the 2,3,6-tri chlorobenzyl compounds, for example, 2,3,6-trichloro 30 benzyl chloride.’ Thus, While, 2,3,6-trichlorobenzy1 chlo ride can be readily formed from 2,3,6-trichlorotoluene, This sul?de can be oxidized upon heating with nitric acid such a route for preparing 2,3,6-trichlorobenzoic acid to form the corresponding ben‘zoic acid and it is believed presents serious difficulties. We have discovered that 2,3,6-trichlorobenzyl chloride 35 that this reaction proceeds as follows: can be converted to 2,3,6-trichlorobenzylamine, 2,3,6 trichlorobenzyl sodium thiosulfate or di(2,3,6-trichloro benzyl) sul?de in good yield and then either one of these last mentioned compounds can be reacted with concen trated nitric acid to form 2,3,6-trichlorobenzoic acid with 40 out e?’ecting substantial ring nitration. ' The 2,3,6-trichlorobenzy1 sodium thiosulfate can be formed by reacting 2,3,6-t1'ichlorobenzy1 chloride with sodium thiosulfate. It is believed that this reaction pro ceeds as follows: 45

CHzCl CHQSS O3Na Thus, each mole of trichlorobenzyl sul?de requires 7 moles of nitric acid. C1 C1 C1 ~Cl The 2,3,6-trichlorobenzyl amine can be formed by re + Nagsgog -——--P + NaOl 50 acting trichlorobenzyl chloride with ammonia in the C1 ——C1 presence of a solvent and, this reaction may be represented by the following equatiom‘ This sodium salt can be readily converted to the acid ‘ 011,01 oniNn, form, trichlorobenzyl thiosulfuric acid, by a strong min 55 or 01 V. 01 _o1 eral acid such as H2SO4,HCl or HNO3 in accordance with + NH3 -—> I + H01 the following reaction using nitric acid: '

OHzSSOaNa CHZSSOaH The trichlorobenzyl amine can be oxidized with nitric I 60 acid and this reaction may be represented by the follow Cl- ~01 C1 C1 ing equation: + HNO; -———> + NaNO3 CH2NH2 00011 ~ C1 —C1 ’

65 01 c1 ' Y ' > I ' i The trichlorobenzyl thiosulfurie acid produced in accord ance with the above reaction or produced in any other U C1 +4HNOsE-—'' . O+3HN02+NOB+NH4NO2 2,899,465 3 . 4. . As shown, each mole of trichlorobenzyl amine requires product apparently was trichlorobenzyl sodium thiosul 4 moles of nitric acid. fate and after drying it weighed 120 g., a yield of 50% In the foregoing oxidation reactions, one mole of 2,3,6 based on the trichlorobenzyl chloride charged. trichlorobenzyl thiosulfuric acid or 2,3,6-trichlorobenzyl The 120 g. (0.38 mole) of product obtained above was amine requires 4 moles of nitric acid while one mole of charged into a reactor along with 430 g. (4.8 mole) of di(2,3,6-trichlorobenzyl) sul?de requires 7 moles of nitric 70% nitric acid over a period of 45 min. On the assump acid. These molal ratios are the stoichiometric amounts. tion that 0.38 mole of the'nitric acid reacted with the Preferably an excess of'nitricTacid is‘ used't‘o increase the trichlorobenzyl sodium thiosulfate, then the molal ratio yield. Large excesses of nitric _acid,mayi,be used. As of trichlorobenzyl thiosulfuric acid to nitric acid was used herein when the term “nitric acid” is accompanied 10 0.38 :4.42 or about 1:12. The charge was heated to re?ux by a percentage ?gure, the ?gure refers to the percentage and held at this temperature for 8 hours. The reaction of nitric acid present in the material used with the re mixture was cooled and ?ltered to separate the crude mainder being water plus the small arnount of impurities trichlorobenzoic acid. This crude product was puri?ed present in commercial nitric acid. Thus,‘ 70% nitric by dissolving it‘ in'dilute-aqueous sodium hydroxide and acid” refers to the fact that the nitric acid used contained 15 then reprecipitating the trichlorobenzoic acid by acidfy about 70% nitric acid and 30% water. Nitric acid of ing the solution with hydrochloric acid. > In ‘this manner other concentrations may be used ‘with the preferred con there was obtained 24 g. (26% yield based on the tri centration being in the'rari‘ge of ‘BO-85%. chlorobenzyl sodium thiosulfate) of trichlorobenzoic acid Example I containing a high percentage of th'e'2,3,6-isomer. 20 Example III Chlorine gas may be passediover the surface ofa body of mixed‘ isomersv of‘trichlorotolue‘ne ‘at "about 205-210° The following materials were charged into a reactor C. until the weight increase corresponds to the theoretical equipped with a re?ux condenser: as determined in accordance ‘with the‘ following reaction: 173 g. (0.75 mole) trichlorobenzyl chloride (mixed iso 25 mers) I (‘3113 (‘513101 66 g. (0.6 mole) potassium sul?de 450 ml. ethanol The mixture was re?uxed for 72'hours, drowned in cold water and the sul?de oil was separated and washed with The mixture’ is then blown with air at 100° ‘C. to remove water. Then 167 g. (0.42 mole) of this di(trichloro any free chlorine and hydrogen chloride present.‘ In this 'benzyl) sul?de was placed’in’a reactor with 810 g. (9 manner trichlorobenzyl chloride ’ may be obtained in moles) of 70% nitric acid. The‘ mixture was heated and re?uxed‘for 6 hours and'then drowned in cold water. 100% yield based on the trichlorotoluene charged. The The crude was separated by ?ltration and'puri?ed by dis isomer or isomers present in the product is the same as solving-in aqueous sodium ‘hydroxide followed by re the isomer or isomers of the starting’ material. In this precipitating with hydrochloric‘ acid. The separated tri particular case a mixture of trichlorotoluene isomers was chlorobenzoic acid which was a'r?ix'tur'e of isomers con~ used in which a major portion consisted of 2,3,’6-trichloro taining a high'lper‘centage of the 2,3,6aisomer weighed toluene and a minor portion consisted of a mixture of the '33 g., 19% yield‘bas'ed ‘on the di(trichlorobenzyl)sul?de. 2,3,4-isorner, 2,3,5-isomer, _ 2,4,5-isomer and 2V,‘4,6_-is'_omer. Accordingly/the trichlorobenzyl chloride was a mixture Example IV of the corresponding isomers in the same‘ proportions. Two hundred thirty-one grams‘ of' mixed isomers of All of the various isomers of trichlorobenzyl chloride trichlorobenzyl.chloride,‘ like that of Example I, were can be prepared in any suitable manner and may be pre charged into'a reactor and their therewas' slowly added pared, for example, by the s'idep'chain chlorination ‘of a solution of 255g. (15 moles)'of"ammonia gas dissolved isomers of trichlorotoluene. While the present invention in 2 liters of methanol while‘cooling‘ to maintain ‘the is primarily concerned with the'production‘of 2,3,6-tri temperature below 20° C. 'The'mixture was then stirred chlorobenzoic acid from 2,3,6-triclilorobenzyl chloride, at room temperature for 72 hours. The excess methanol the other isomers of trichlorobenzoic acid can be pre "and ammonia'were removed'under’ partial vacuum. The pared in the same manner. In general, the arrangement 50 residue was treated withi'200'g. of'40%‘sodii1m'hydroxide ofthe three chlorine atoms on the ring in the trichloro solution‘ and then‘ extractedwith two-one liter portions benz'oic acid are 'the sanie as ‘the arrangement in the start of ether. The combined extracts werejdriedt over anhy ing material. The trichlorobenzoic acids which do not drous sodium sulfate and then evaporated to dryness. contain the 2,6,-arrangement_are, if anything, more readily The product, ‘crude trichlorobenzyl amine, weighed 205 produced as these other isomers are more reactive. The g., a yield of 97.4% based on the trichlorobenzyl chloride spatial arrangement of the 2,3,6 isoir'ier renders it ‘less charged. reactive. Such a mixture ~of isomers was useid'in the‘fol The 205 g. (.97 mole) of product obtained above was lowing examples so that the itrichlo'r'obenioicacidr'pro cooled to 10° C. and mixed with 1080 (12 moles) of 70% duced was a’ mixture'of isomers with 2,3,6itrichlor'oben 60 nitric acid. The mixture was stirred at room temperature zoic acid predominating. Pure ' or substantially pure for 30 min. and then heated at re?ux for 8 hours. The 2,3,6-trichloroben‘zyl chloride may be used" in the same reaction was then‘ cooled to‘ room‘ temperature “and the manner. spent'acid'was decanted from the residual crude trichloro~ Example 11 ben'z'o'id acid Two 1250 ml. portions of water were used The following materials were charged into a reactor to wash the residue which‘ was" then dissolved in 2000 g. equipped with a re?ux condenser: of 10% sodium hydroxide. This solution was treated with 500 ml. of chloroform to remove the alkali insoluble 173‘ g. (0,75'm'ole) trichlorobenzyl chloride',‘mixedisomers impuritities. The solution was then treated with 10 g. of 230g. (1.5 mole) ‘sodium thio‘sulfa'te' activated charcoal to effect decolorization, ?ltered, and 600 g. water 70 acidi?ed with 500 ml. of ‘concentrated hydrochloric acid 500 g. ethanol to recrystallize the trichlorobenzoic acid. The precipi The mixture was heated and re?uxed for 8lhours, then tate was separated by ?ltration, washed with water and cooled and the liquor decanted from the residue present. air dried at 50° C. The product weighed 97.5 g., 43.3% The liquor was concentrated under partialvacuum to yield based on the’tr'ichlorob'enzyl amine. 500 ml., cooled and ?ltered to separate the product. This 75. In each of Examples II, III and IV, the trichlorobenzyl 2,899,465 5 6 chloride was a mixture of isomers containing a high per consisting of 2,3,6-trichlorobenzyl thiosulfuric acid, 2,3,6 centage of the 2,3,6-isomer such as described in Example trichlorobenzylamine and di(2,3,6-trichlorobenzyl) sul?de I. Accordingly, the trichlorobenzoic acid product was a with an amount of 60-85% nitric acid in excess of the mixture of isomers containing a high percentage of 2,3,6 stoichiometric amount to form 2,3,6-trichlorobenzoic acid trichlorobenzoic acid. Other isomer mixtures could be separating crude 2,3,6-trichlorobenzoic acid from the re used ‘as well as pure or substantially pure, 2,3,6-trichloro sulting reaction mixture, dissolving the separated crude benzyl chloride as a starting material. 2,3,6-trichlorobenzoic acid in an aqueous solution of an We claim: alkaline, alkali metal compound, treating the solution 1. In the process of producing 2,3,6-trichlorobenzoic with mineral acid to precipitate the 2,3,6-trichlorobenzoic acid, heating at re?ux temperature under atmospheric 10 acid, and separating the precipitated 2,3,6-trichloroben pressure a trichlorobenzyl compound selected from the zoic acid. group consisting of 2,3,6-trichlorobenzyl thiosulfuric acid, 6. In the process of producing trichlorobenzoic acid, di-(2,3,G-trichlorobenzyl) sul?de and 2,3,6-trichloroben the steps comprising re?uxing under atmospheric pres zylarnine with ‘an amount of concentrated nitric acid in sure a trichlorobenzyl compound selected from the group excess of the stoichiometric amount to form 2,3,6-tri 15 consisting of trichlorobenzyl thiosulfuric acid, di-(tri chlorobenzoic acid. chlorobenzyl) sul?de and trichlorobcnzylamine with at 2. In the process of producing 2,3,6-trich1orobenzoic least the stoichiometric amount of concentrated nitric acid, the steps comprising re?uxing 60-85% nitric acid acid to form trichlorobenzoic acid, said trichlorobenzyl under atmospheric pressure with 2,3,6-trichlorobenzyl compound and said trichlorobenzoic acid each having a thiosulfuric acid in a molal ratio greater than 4 to form chlorine atom in the 2—position and the 6-position on the 2,3,6-trichlorobenzoic acid, and then recovering the 2,3,6 ring. trichlorobenzoic acid. 3. In the process of producing 2,3,6-trichlorobenzoic References Cited in the ?le of this patent acid, the steps comprising re?uxing 60-85% nitric acid UNITED STATES PATENTS under atmospheric pressure with 2,3,6-trichlorobenzy1 1,878,462 Britton ______Sept. 20, 1932 amine in a molal ratio greater than 4 to form 2,3,6-tri 2,172,954 Clark ______Sept. 12, 1939 chlorobenzoic acid, and then recovering the 2,3,6-tri 2,195,539 Mikeska et al ______._ Apr. 2, 1940 chlorobenzoic acid. 2,606,208 Burtner ______Aug. 5, 1952 4. In the process of producing 2,3,6-trichlorobenzoic 30 2,618,657 Vaughn et a1. ______..... Nov. 18, 1952 acid, the steps comprising re?uxing 60-85% nitric acid 2,635,114 Schlatter ______Apr. 14, 1953 under atmospheric pressure with di(2,3,6-trichloroben 2,666,786 Kulka et a1. ______. Jan. 19, 1954 zyl) sul?de in a molal ratio greater than 7 to form 2,712,547 Lecher ______.. July 5, 1955 2,3,6-trichlorobenzoic acid, and then recovering the 2,3,6 2,740,811 Lotz ______Apr. 3, 1956 trichlorobenzoic acid. 5. In the process of producing 2,3,6-trichlorobenzoic 35 OTHER REFERENCES acid, the steps comprising re?uxing at atmospheric pres Brimelow: J. Chem. Soc., pp. 1208-12 (1951). sure a trichlorobenzyl compound selected from the group Brimelow: Chem. Abs., vol. 46, col’s. 2002-3 (1952).