CS257071B1 - A method for purifying and isolating a mixture of 4,4'- and 2,4'-dihydroxydiphenylsulfones - Google Patents

Abstract

The solution concerns a method of purification and isolation of a crude mixture of 4,4'-dihydroxydiphenylsulfone in an alkaline medium using carborafin and sodium dithionate. The mixture of dihydroxydiphenylsulfones is the basic raw material for the preparation of 4-benzyloxy-4'-hydroxydiphenylsulfone, an intermediate for the production of color-forming components

Description

The present invention provides a process for purifying and isolating 4,4-a '2,4'-dihydroxydiphenylsulfone from the reaction mixture.

Industrially significant 4-benzyloxy-4'-hydroxydiphenylsulfone is prepared by benzylating 4,4'-dihydroxydiphenylsulfone (Organic Synthesis 25, 9, 1945; CS AO 234 520). However, the preparation of pure 4,4'-dihydroxydiphenylsulfone (III) is quite complex. In a number of earlier works, its prepared is carried out by heating phenol (i) for several hours at 160-180 ° C with fuming sulfuric acid (II) while distilling off the water and after completion of the reaction pour the reaction mixture into water. The recrystallized product was considered to be a uniform 4,4'-dihydroxydiphenylsulfone (III). (Glutz: Liebig's Analen der Chemie 147.2; Annaheim: item 172.36).

OH

HO (I) (III) (IV)

Later, however, it has been shown (for more precise analytical methods) that the product thus prepared contains, in addition to the 4,4'-isomer (III), 4,2'-dihydroxydiphenylsulfone (IV), the separation of which is carried out by very complex and technologically inconvenient crystallization from acetone. abenzene (Hinkel LE, Summers GHR: Journal of Chemical Society 1949, 2,855). In addition, the crude mixture of 4,4'- and 2,4'-dihydroxydiphenylsulfones (hereinafter "diphenylsulfone") is contaminated with resinous and colored substances of uncertain composition. The resinous fractions are removed to a certain extent by simply boiling the crude mixture with water, the colored substances are not removed in this way and have an adverse effect on the further processing of the product. Various methods for purifying colored diphenylsulfone, such as purifying a methanolic or aqueous-alkaline solution of diphenylsulfone with an active angle (Jap. Pat. 5 247/73 and 36 264/76), extracting colored substances from diphenylsulfone with phenol (Ja-OS 11), are described in the technical literature. Or higher aliphatic alcohols under pressure at 120 ° C (Jap. Pat. 3 005/67).

The above processes do not provide sufficiently pure diphenylsulfone that could be used to activate polymerization reactions. According to ain. U.S. Pat. 2, 088, 857 and DE Pat. 3, 141, 454, is purified by diphenylsulfone by reduction with various reducing agents such as sodium formaldehyde sulfoxylate, sodium borohydride, sodium dithionite appd. in organic solvents or in an aqueous-alkali solution in the presence of nitrilotrioxtic acid, ethylenediaminotetraacetic acid or diethylenetriaminopentaacetic acid. This procedure yields a diphenylsulfone of purity purportedly sufficient to use diphenylsulfone as an intermediate for the synthesis of color photographic substances, for example in the preparation of colorformers, which is still unsatisfactory.

It has now been found that diphenylsulfone in a purity suitable for photographic purposes is obtained by combined purification with carborafine (activated carbon) and reducing agents in an aqueous alkaline solution at a temperature of about 80 ° C.

A pure mixture of 4,4'- and 3,4'-dihydroxydiphenylsulfones, devoid of any resins and colorants, is obtained by basifying the reaction mixture obtained after the reaction of the sulfuric acid with the phenol is exported with carboraffin, the carboraffin together with It is filtered and the red-colored filtrate containing the rest of the dyes is decolorized with a solution of 2 to 5% sodium dithionate.

The obtained practically colorless solution is acidified hot with conc. hydrochloric acid to congo with stirring. After cooling to 20 ° C, the precipitated substance is filtered off with suction.

The substance and satisfactory purity could not be prepared simply by boiling with carboraffin, not even by decolorizing the filtrates after boiling in carboraffin free water. A combination of both purification methods is necessary to achieve a product of acceptable purity.

The crude product does not need to be isolated and additionally purified, but the purification process can be incorporated directly into the reaction process by pouring the reaction mixture into hot water, adding carboraffin and heating to boiling after completion of the reaction. The reaction mixture is then filtered and the filtrate is decolorized with sodium dithionate.

The advantages of the above process are the simple method of purifying the mixture of 4,4'- and 2,4'-dihydroxydiphenylsulphon from their resinous color impurities and the simple method of isolation from the reaction mixture.

Example

To a 6000 ml descending condenser, thermometer and stirrer flask was charged with 613 ml of fuming sulfuric acid (monohydrate) with 2000 g of phenol, and the mixture was rapidly heated to 180-190 ° C with vigorous stirring. After distilling off the reaction water, it is poured into 19 l of hot water containing 250 g of sodium hydroxide. 300 g of carboraffin are added and the reaction mixture is maintained at 80-100 ° C for 1 hour with stirring. Then, the carboraffin, together with the resin and coloring substances, is filtered off and the filtrate is decolourised with a 2 to 5% sodium dithionate solution in the hot state. The colorless solution was acidified with conc. hydrochloric acid to congo. The suspension is cooled to 15-20 ° C and the precipitate is filtered off with suction and washed with water until neutral. A white solid, m.p. 209 DEG-244 DEG C. in a yield of 1951 g, i.e. 70% of theory.

Claims (1)

SUBJECT OF THE INVENTION Process for purifying and isolating a mixture of 4,4'- and 2,4'-dihydroxydiphenylsulfone of formulas III and IV HIM OH + HOHO (III) (IV) characterized in that the alkaline solution of their crude mixture is boiled with carboraffin and after filtration the filtrate obtained is decolourised with sodium dithionate solution and the resulting colorless solution is acidified with conc. hydrochloric acid to congo.