DE597242C - Process for the preparation of 1-chloro-2-methylanthraquinone by chlorination of 2-methylanthraquinone in weak oleum - Google Patents

Description

It is already known i-chloro-2-methylanthraquinone by chlorination of 2-methylanthraquinone in weak oleum means to produce elemental chlorine. In doing so, 5 oleum will have a strength of not over approximately 20 0/0 used.

The purpose of the invention is to improve the known method. It turned out as a result of a number of investigations that despite the teaching that chlorination and bromination should be carried out at relatively high temperatures, rarely only at normal room temperatures, the chlorination in the process mentioned already at low temperatures, e.g. B. around o ° begins. Characterized in that such low temperatures selected, namely those of the order of o ° and not greater than about 15 ^0, are obtained many advantages. For example, it has been found that when chlorinating at elevated temperatures there is a possibility that the product may be mixed with isomers which do not contain the chlorine in the 1-position. By using the lower temperature, the amount of isomers is further reduced, while the proportion of 1-chloro-2-methylanthraquinone is increased. The product obtained is therefore much more suitable as an intermediate product for the production of pyranthrone or the like than what has been obtained up to now. It is well known that the entry of the halogen into any position other than the i position is worthless for this purpose.

The 1-chloro-2-methylanthra- ₍ quinone) obtained in this way is much more valuable for the production of the i-chloro-2-carboxylic acid of anthraquinone, which is an intermediate product in the production of anthraquinone-i, 2-naphthacridone (Caledon Rot BN) as the substance obtained by the known method described above.

The process is particularly useful in the conversion of 4'-methyl-2-benzoylbenzoic acid into the 1-chloro-2-carboxylic acid of anthraquinone in one process (cf. British patent specification 207 840).

Briefly summarized, the invention is that ¹ 2-methylanthraquinone in weak oleum, ζ. B. in oleum in a strength of not more than about 20 0/0, at temperatures around ⁰ ° C and not above about 15 0 C is chlorinated.

The 2-methylanthraquinone can then be prepared in one process be converted into the 1-chloro-2-carboxylic acid of anthraquinone.

The products made in this way are used to manufacture pyranthrone, anthraquinone-1, 2-naphthacridone and the like are used.

3046!

MICROFILMED BY FIAT

The following examples illustrate the practice of the invention. Parts and Percentages mean parts by weight and percentages by weight.

Example ι

130 parts of 2-methylanthraquinone and 4 parts of iodine are dissolved in 1,300 parts of 3.5% oleum. Chlorine is then passed in at a rate of 6 parts per hour with stirring, the temperature still being maintained at 1 2 ⁰ . A total of about 45 parts of chlorine are reacted. After the last amount of chlorine has been introduced

The stirring is continued for another 2 or 3 hours long away, then takes a sample and analyzes it. When the chlorine level is below the theoretical value, a further amount can be made to react. The exact amount of what is necessary Chlorine depends to a certain extent on the apparatus used, but it depends on one or two chlorinations no longer necessary to determine by taking a sample, when the chlorination is finished. After the chlorination becomes the sulfuric acid solution Poured into 13,000 parts of water, then boiled, allowed to settle, and the supernatant siphoned off The solution is removed, the batch is filtered off, washed with a little 10% soda solution, and finally with it pure water and dry.

Example 2

14 parts of 4'-methyl-2-benzoylbenzoic acid are sprinkled into 130 parts of 50% oleum. The mixture is heated to iio °

and keep it at this temperature for 3 hours. Then you cool off. You bet on that Sufficient 230% oleum is added to reduce the strength of the oleum to 3.5 to 4% of free sulfur trioxide bring to. 1.3 parts of iodine are added, whereupon chlorine is passed in and while maintaining the temperature at 0 ° until the chlorine content of the reaction mass is approximately 13.80 / 0.

The mass is then blown into enough water _{to dilute the acid to about 5 o / o} sulfuric acid, then boiled, filtered, washed acid-free and dried.

The invention is not restricted to the examples given above. After the described One can process i-chloro-2-methylanthraquinone obtained almost entirely free of isomers conveniently and richly in a practically useful manner.

Claims (2)

Patent claims: 1. Process for the preparation of i-chloro-2-methylanthraquinone by chlorination of 2-methylanthraquinone in weak oleum, characterized in that one carries out the chlorination at temperatures around 0 ° and not above about 15 °. 2. The method according to claim 1, characterized in that the oleum solution of 2-methylanthraquinone, as is known in the art by condensation of the 4 '- methyl - 2 - benzoylbenzoic acid is obtained by means of sulfuric acid, up to the in-essence concentrated free sulfur trioxide and then chlorinated.