DE2010535A1 - Process for the preparation of 2,4-dihydroxybenzophenone - Google Patents

Description

BORSODI VEGYI KOMBINAT Kazincbarcis, Hungary

PROCESS FOR THE PREPARATION OF "2,4-DIHYDRQXYBENZOFFrENONE

The 2,4-dihydroxybenzophenone is mainly used in the Plastics industry, but also widespread in other areas Used as a so-called ultraviolet absorber, it also serves as a starting material for the production of numerous important compounds, mainly ultraviolet absorbers. It is therefore easy to understand, since! 3 parallel with the high-grade. Dissemination of plastics revealed growing interest in this compound.

The 2,4-dihydroxybenzophenone was still at the end of the

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Manufactured for the first time in the last century. Apparently one of the simplest syntheses of this compound was created by A. Komarowski and St.v. Kostanecki communicated. (Derichte of the German Chemical Society, £ 2, 1997 / 1890 /). Benzotrichloride was in an aqueous medium with Reocrcin brought into reaction, whereby in addition to numerous colored and other by-products also 2,4-Dihydroxyfcenssoph.enon was won. Already these authors stated that the connection with the method they described only can be produced in low yield and that the purification of the crude product is very difficult to carry out. Some Later, Pfeiffer obtained 2,4-dihydroxybenzophenone with the same starting substances in an alcoholic medium (Annalan, 398 »165/1913 /). In this reaction it forms but understandably in large quantities of ethyl benzoate, its separation from 2,4-dihydroxybenzophenone extremely is difficult and, owing to its formation, the yield is also very low.

Other processes for the production of 2,4-dihydroxybenzophenone were later worked out, but they are all complicated, expensive and labor-intensive, since either other, more difficult-to-access compounds are used as the starting substance, such as benzoylchlorld or benzonitrile, or a completely anhydrous medium is required and cumbersome treatable and from the reaction mixture only with schwerfHlligen methods ent fernbare catalysts such as Zinkchl'orid, boron trifluoride, phosphorous pentoxide, phosphoric acid, phosphorus trichloride "aluminum chloride, tin tetrachloride, etc.

It has now been found, surprisingly, that the reaction of the benzotrichloride and resorcinol gives the 2,4-dihydroxybenzophenone with a 91 to 98% yield, based on the theoretical; Amount and in a degree of purity appropriate for most practical purposes provides »if the reaction takes place at a temperature range of 50 to 120 ⁰ C,

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BATH ORIGINAL- '

preferably from 95 to 105 ^° C. in an aqueous acetic acid medium which contains at least the amount of water stoichiometrically necessary for the reaction, but advantageously consists of 30 to 50 % acetic acid and 70 to 50% water. In contrast to practical experience that, in addition to benzotrichloride and resorcinol, both in pure water and in pure acetic acid, 2,4-dihydroxybenzophenone contaminated with numerous, mainly strongly colored by-products can only be obtained with low yield In the case of the process according to the invention, ie in acetic acid containing a fixed amount of water, secondary reactions are negligible, the product is hardly colored and the yield is excellent. In addition to its technical advantages, the process according to the invention is also very advantageous from an economic point of view, since the starting substances can be purchased easily and cheaply, the yield is high and the acetic acid used as a medium can be used again as often as desired after simple regeneration.

The implementation of the method according to the invention is explained in more detail using the following examples:

example 1

18.75 kg of water, 12.50 kg of acetic acid and 3.50 kg of resorcinol are weighed into a reactor equipped with a reflux condenser, stirrer and thermometer. The reactor is closed and its contents are heated ^{to 50 ° C. with stirring} constant stirring over the course of 3 hours, 10.3 kg of benzotrichloride are fed into the reactor, during this time heating or, if necessary, cooling ensures that the temperature of the reaction mixture is constantly between 90 and 95 ^° C. The during the Hydrochloric acid vapor formed in the reaction and escaping from the reaction mixture is diverted. After the addition of the benzotrichloride has ended, the temperature of the reaction mixture is increased to 100 to 105 ° C and a further 30

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The reaction device is kept at this temperature for minutes. It is then cooled to 10 to 15 ^° C., the crystalline 2,4-dihydroxybenzophenone which separates out is collected on a filter, washed acid-free with water and dried.

The yield was 9.70 kg, 91 # of theory.

example 2

Proceed as in Example 1, with the difference that the following amounts of substance are weighed into the reactor:

26.00 kg of water,

11.50 kg acetic acid,
5.50 kg resorcinol,

IC, 30 kg benzotrichloride.

The yield was 9.70 kg, 91 % of theory.

Example 3

The procedure is as in Example 1, with the difference that the following amounts of substance are weighed into the reactor:

15, OC kg of water,

10.00 kg acetic acid,
5.5 kg resorcinol,

10.30 kg of benzotrichloride.

The yield was 10.50 kg, 98 % of theory.

Example 4

Proceed as in Example 1, with the difference that the following substances are weighed into the reactor:

12.50 kg V / a33er,

12.50 kg acetic acid,
5 »50 kg resorcia,

12.30 kg of benzotrichloride.

The yield was 10.25 kg, 95 # of theory.

The quality of the products obtained according to the above examples is equivalent for most practical purposes

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BATH ORIGINAL

If necessary, they can be cleaned using the known methods. Their melting point is 144 to 145 ^° C

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Claims (1)

PATENTAN PRlTCH A process for the preparation of 2,4-dihydroxybenzophenone, by the reaction between resorcinol and benzotrichloride, characterized in that the Heaktion in the temperature range of 70 to 120 ⁰ C, expediently of 95 to 105 ⁰ C in an acetic acid-water mixture. is performed, and the mixture contains at least the time necessary for the reaction, calculated amount of water, preferably from 30 bi3 # 50 consists of acetic acid and 50 to 70 H "water." 009840/2229