Patent GB-318837-A (GB)
IPC: C07C309/48
Filed: 1929-09-09
Abstract: 318,837. I. G. Farbenindustrie Akt.- Ges. Sept. 7, 1928, [Convention date]. 1-Methyl- 2-halogen- 3 -chlor- 4 -aminobenzene- 5-and-6-sulphonic acids.-By sulphonating 1- methyl-2-halogen-3-chlor-4-aminobenzene with monohydrate at 180-200‹ C., or at 100-130‹ C. with fuming sulphuric acid containing a molecular proportion of sulphur trioxide, the corresponding 5-sulphonic acid is obtained, whereas sulphonation with oleum containing an excess of sulphur trioxide gives the 6-sulphonic acid. When a mixture of the parent body, with 1- methyl-2-halogen-5-chlor-4-aminobenzene is sulphonated, the latter remains unattacked and may be separated. The method may accordingly be used for separating the two bases; the mixture of the two bases is treated with sulphuric mono hydrate and the resulting 1-methyl-2-halogen-3- chlor-4-aminobenzene-5-sulphonic acid, after separation of the 1-methyl-2-halogen-5-chlor-4- - aminobenzene heated with dilute sulphuric acid to remove the sulphonic group. According to examples; (1) 1-methyl-2: 3-dichlor-4-aminobenzene and 1-methyl-2-brom-3-chlor-4-aminobenzene (prepared by the method of Specification 294,078) are sulphonated with monohydrate at 180-200‹ C. to give the corresponding 5-sulphonic acids; (2) 1-methyl-2 : 3-dichlor-4-aminobenzene is sulphonated, using oleum containing a molecular proportion of sulphur trioxide, in order to obtain the 5-sulphonic acid; (3) 1-methyl-2 : 3-dichlor-4- aminobenzene is sulphonated, using oleum containing excess sulphur trioxide. The precipitated 6-sulphonic acid obtained on pouring on to and adding salt is freed from a small amount of the 5-sulphonic acid by forming a weakly alkaline solution therof by the addition of caustic soda, and filtering. The soluble alkali salt of the 1- methyl - -2:3- dichlor - 4 - aminobenzene - 6 - sulphonic acid, on precipitation by adding hydrochloric acid, yields the corresponding free acid; (4) a mixture of 2 : 3-dichlor- and 2 : 5-dichlor-4- amino-1-methyl benzenes is sulphonated, using oleum containing large excess of sulphur trioxide, the unchanged 1-methyl-2: 5-dichlor-4-amino-1 methylbenzene separated from the alkali solution of the products, and the 1-methyl-2: 3-dichlor-4- aminobenzene-6-sulphonic acid worked up as in example (3) above; (5) a mixture of 2 : 3-dichlor- and 2 : 5-dichlor-4-amino-1-methylbenzenes is sulphonated with monohydrate, and the former isolated as 1-methyl- : 3-dichlor-4-aminobenzene-5- sulphonic acid after separation of the latter uncharged. By heating with aqueous sulphuric acid the sulphonic group is removed from the 1-methyl- 2: 3-dichlor-4-benzene-5-sulphonic acid. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the following examples : (1) 1-methyl-2-brom-3-chlorbenzene is sulphonated using excess oleum to give 1-methyl- 2-brom-3-chlorbenzene-6-sulphonic acid : (2) a mixture of 1-methyl-2-brom-3-chlor- and 1-methyl- 2-brom-5-chlorbenzene is sulphonated with oleum containing 1 mol. sulphur trioxide. The products are separated by treating the heated presscake paste with ammonia or magnesia and then extracting with an organic solvent, such as chlorbenzene, dichlorbenzene or tetrachlorethane, which removes the unchanged 1-methyl-2-brom-5-chlor 4-aminobenzene. The 1-methyl-2-brom-3-chlor-4- aminobenzene-5-sulphonic acid, in the form of its ammonium or magnesium salt, is heated under pressure with sulphuric acid whereby the sulphate of 1-methyl-2-brom-3-chlor-4-aminobenzene is obtained, which is finally converted into the free base by means of alkali. 2:3-Dichlor-1-methyl-4-aminobenzene in admixture with 2 : 5-dichlor-1-metlyl-4-aminobenzene may be prepared by the action of chlorine, in the presence of acetic anhydride, upon the acetvl derivative of 1-chlor-4-amino-1-methylbenzene (which may be prepared by heating the latter with acetic anhydride), and saponifying the mixture of the two isomeric dichlor-4-acetylamino-1- methylbenzenes by means of sulphuric acid. The resulting mixture of the two sulphates are then decomposed by means of alkali. - 2 - Brom-3-chlor-4-amino-1-methylbenzene admixed with 2-brom-5-chlor-4-amino-1-methylbenzene may be prepared by chlorinating 2-brom- 4-acetylamino-1-methylbenzene, saponifying with sulphuric acid, and liberating the mixture of the free bases by means of alkali. This subjectmatter does not appear in the Specification as accepted.