DE1543823B - Process for the preparation of 2,4-dihydroxybenzophenone - Google Patents

Description

After driving off volatile substances from the reaction mixture, preferably by steam distillation, the mixture is cooled and filtered. The 2,4-dihydroxybenzophenone obtained as filter residue is washed with water and dried.

The amount of benzonitrile in the process according to the invention must be at least 2 moles per mole of resorcinol be. An amount of 2 moles is sufficient to achieve the highest yields and is therefore preferred. If there are difficulties in stirring the reaction mixture, larger ones can be used Add amounts of more than 2 moles of benzonitrile per mole of resorcinol, in which case the excess benzonitrile as a diluent works. The addition of more than 4 moles of benzonitrile per mole of resorcinol is usually unnecessary.

The amount of zinc chloride to be used is 0.3 to 1 mole per mole of resorcinol.

2,4-Dihydroxybenzophenone is used as an absorbent for ultraviolet light in resins and plastics, such as polystyrene, polymers of acrylonitrile and polymers and copolymers of acrylic acid and methacrylic acid esters, used. It is also suitable as an intermediate for manufacturing other ultraviolet absorbers, e.g. B. various ether derivatives.

In the following example, the parts refer to amounts by weight.

example

165 parts (1.5 moles) of resorcinol and 120Teile (0.74 mole) of anhydrous zinc chloride are added to 309 parts (3.0 mol) of benzonitrile, and the mixture is stirred for ¹ J ₂ hours at about 25 to 30 ° C. Gaseous hydrogen chloride is then passed in over the course of several hours until the reaction mixture is saturated or a total of about 95 to 109 parts (2.6 to 3.0 mol) of hydrogen chloride has been absorbed. The reaction mixture is kept at 50 ° C. for 8 hours, during which the hydrogen chloride which is evolved is allowed to escape. 800 parts of cold water are then gradually added and the reaction mixture is stirred for several hours at room temperature. The reaction mixture is then subjected to steam distillation in order to drive off volatile products. The mixture is then cooled and the 2,4-dihydroxybenzophenone is filtered off, washed with water and dried. 300 parts of 2,4-dihydroxybenzophenone are obtained (yield 93.3%> based on the resorcinol used) with a melting point of 143 to 144 ° C and a pure

degree of 97% "

Claims (2)

U.S. Patent 2,773,903). This process is disadvantageous because it works with ether and, moreover, does not achieve any ketone yields greater than 40%. When using other 1. A process for the preparation of 2,4-dihydroxy 5 ren solvents as ethers, z. B. glacial acetic acid, mixtures of benzophenone by reacting benzonitrile with chloroform and ether, methyl acetate or ethyl resorcinol in the presence of zinc chloride and chlorobromide, one gets even lower yields, hydrogen and subsequent hydrolysis of the um- The invention was therefore based on the object , a settlement product, characterized by an economic process for the production of 2,4-Dizeichnet that the conversion into Abio hydroxybenzophenone of high purity to putrefaction of solvents or diluents, which carried out without a solvent with a molar ratio of benzonitrile can be recovered and provides significantly higher yields of at least 2: 1 at 10 to 85 ⁰ C ih counter- than the previously known processes. Was from 0.3 to 1 mole of zinc chloride per mole of resorcinol. The process according to the invention for production and that of 2,4-dihydroxybenzophenone to saturate the reaction mixture by reacting The required amount of hydrogen chloride is carried out using benzonitrile with resorcinol in the presence of Zihkchlo- the hydrolysis after the cessation of the strong rid and hydrogen chloride and subsequent hydrolysis Carries out hydrogen chloride development. of the reaction product is characterized by 2. The method according to claim 1, characterized in that the implementation is drawn in the absence of solution, that the reaction at about 50 ° C 20 or diluents with a molar ratio of performs. Benzonitrile to resorcinol of at least 2: 1 at 10 to 85 ⁰ C in the presence of 0.3 to 1 mol of zinc chloride each Moles of resorcinol and that to saturate the reaction mixture required amount of hydrogen chloride through-25 and the hydrolysis after the cessation of the strong Develops hydrogen chloride. The invention relates to an improved process which is preferably carried out by filtering from the reac- for the production of 2,4-dihydroxybenzophenone. tion mixture obtained 2 _; 4-dihydroxybenzophenone The usual process for the preparation of 2,4-di- is of high purity and falls in yields of more hydroxybenzophenone is based on a Friedel-Crafts 30 as §0% of the theory, based on the re-reaction used, in the case of benzoyl chloride with resorcinol in sörciii; on. The inventive method requires In the presence of aluminum chloride, neither the presence of ether nor that of ir- (cf. H ο u b e η and Fischer, reports of the significant another solvent or diluent, see chemical society, Vol. 6Ö, 1927, p. 1759 In the process according to the invention, the gas to 1778, and Chemical Abstracts, Vol. 22, 1928, 35 formed hydrogen chloride, preferably with stirring P. 237). This method requires large amounts of a mixture of resorcinol, at least about 2 moles Aluminum chloride. Benzonitrile per mole of resorcinol and zinc chloride, preferably US Pat. No. 3,073,866 teaches a process in a closed vessel, added so long, for the production of hydroxy-alkoxy-arylphenones until the mixture is saturated with hydrogen chloride or, for example, of 2,4-dihydroxybenzophenone, by 4 ° approximately 1.6 to 2.0 moles of hydrogen chloride per mole of resorcinol condensing an aryl carboxylic acid with a phenol have been absorbed. The hydrogen chloride or phenol alkyl ether in the presence of zinc chloride, above or below the surface of the reaction mixture phosphorus trichloride and phosphoric acid. be directed. The pressure in the vessel is not sufficient From Recueil des Travaux chimiques des Pays-bas 50, decisive and can rise within the limits set by the Reak-1931, pp. 848 to 850 is a method for the production of 45 tion vessel,
of acylresorcins by condensation of acid- When the hydrogen chloride is added, the temperature chlorideii known as BenzyöichioHd with excess resofratur of the reaction mixture in the range from 10 to one. 85 ⁰ C held. The reaction is preferably However, these methods require for their implementing tion mixture to about 25 ⁰ C, if one result UIID with the Einrung a greater technical effort 50 guided by hydrochloric beginiit because the Ge'misch lower yields than the present invention is viscous at lower temperatures and procedural is difficult to stir. At temperatures above 85 ° C Another method for the production of 2,4-diene yields. Usually the reaction hydroxybenzophenone has to be cooled under the name mixture, in order to make the temperature known as "Hoesch reaction" 55 85 ⁰ G to fialton: This procedure is usually carried out after the addition of hydrogen chloride is complete by opening the reaction vessel to the outside with a mixture of equimolecular quantities, and stirring the resorcinol and benzonitrile III present vdü zirikchlo mixture until the strong hydrogen chloride and dry ether with gaseous hydrogen chloride development has ceased, which is usually not saturated with substance. If the complete implementation takes longer than 10 hours. Here, the Tempeist, the reaction product is maintained by the addition of temperature in the range of 10 to 85 ⁰ C, preferably hydrolyzed in water to 2,4-dihydroxybenzophenone about 5O ⁰ C,. (cf. “The Hoesch Synthesis” vin S ρ ο e r r i and The resulting reaction product then becomes Du B o is in "Organic Reactions", Vol. V, Chapter 9, hydrolyzed to 2,4-dihydroxybenzophenone. At the Wirt-Verlag John Wiley and Sons, Inc., New York, 1949; In the most economical way, hydrolysis is carried out by adding O 1 ah: "Friedel-CraftsandRelatedReactions", Vol. III, water for the reaction mixture and several hours Part 1, Chapter XXXII - »Houben-Hoesch and ReIa- stirring. Feuchtigted should be used until hydrolysis begins Syntheses ", Ruske, Interscience Publishers, 1964; ability to be kept away from the reaction mixture.