GB1574441A

GB1574441A - Preparation of hydroxybenzophenones

Info

Publication number: GB1574441A
Application number: GB28674/76A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1976-07-09
Filing date: 1976-07-09
Publication date: 1980-09-10
Also published as: JPS539735A; FR2357517A1; UST970006I4; DE2730991A1

Description

(54) PREPARATION OF HYDROXY-BENZOPHENONES (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London, SW1P 3JF a British Company do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the manufacture of halophenols and in particular to the manufacture of halophenols of formula

where Xis halogen. The halogen atom X is preferably ortho or para to the group CO. Such halophenols may be polymerised to form polyetherketones, e.g. by conversion to the corresponding alkali metal salt which may be self condensed, in the melt, or in an inert solvent, such as sulpholane or diphenyl sulphone, as described in British patent specification 1153 035. Alternatively the halophenol can be polycondensed by reaction with an alkali metal carbonate, for example as described in Canadian patent specificaton 847 963.

The halophenols are thus valuable chemical intermediates in the manufacture of polymers.

Methods of making such halophenols previously proposed include hydrolysis of one halogen atom of a dihalide

where the halogen atoms X are ortho or para to the group CO, with an alkali in the presence of an ionising solvent, e.g. dimethyl sulphoxide, followed by conversion of the alkali metal mono salt to the corresponding halophenol. Such a process is proposed in British patent specification 1 153 035. However the dihalides are relatively expensive materials. An alternative method involved the hydrolysis of a carbonate or phosphorochloridate of formula

where Y = CO (in which case n = 2), or POCl2 (in which case n = 1). Such a process is described in British patent specification 1 357 344.

These precursors to the halophenols were themselves made by Friedel Crafts condensation of the compounds

where one of R and R' was -CO-X and the other was -H.

We have now devised a simpler way of making the halophenols.

Accordingly we provide a process for the manufacture of halophenols of formula

where X = halogen, comprising condensing a halo-substituted benzoic acid, or acid halide derivative thereof, of formula

where Z is OH or halogen, with phenol in the presence of a molar excess of liquid anhydrous hydrogen fluoride.

Compounds which may be condensed with phenol are thus halobenzoic acids or the corresponding acid halides. The use of the acids as opposed to the acide halides is preferred.

The halogen atom X is preferably ortho or para, particularly the latter, to the -COgroup.

The halogen is preferably fluorine, chlorine or bromine. Of these chlorine is preferred for economic reasons while fluorine is preferred as the resultant halophenol is more reactive.

As a modification of the invention the fluorophenols

may be made by a process wherein the fluorobenzoic acid or acid halide derivative thereof is made in situ by reaction of the corresponding aminobenzoic acid or acid halide with an alkali metal nitrite, e.g. sodium nitrite, in at least one mole of liquid anhydrous hydrogen fluoride. The alkali metal nitrite should be employed in at least a slight molar excess.

Hence the fluorophenols may be made by reaction of

with a molar excess of an alkali metal nitrite and of phenol in at least two moles of liquid anhydrous hydrogen fluoride. In this process the amino compound is preferably p-aminobenzoic acid, giving as the fluorophenol, 4-fluoro-4'-hydroxybenzophenone.

These reactants are condensed in substantially equimolar amounts although a slight excess of the phenol may be employed if desired. An excess of the substituted benzoic acid or an acid halide derivative thereof is less desirable because of the risk of disubstitution reactions.

The condensation is catalysed by liquid anhydrous hydrogen fluoride which may also act as a diluent. An amount of hydrogen fluoride well in excess of the molar proportion specified is preferred.

The hydrogen fluoride may be recovered and recycled.

The reaction is preferably carried out at 20-1000C.

The invention is illustrated by the following Examples.

Example I 4-chlorobenzoic acid (31.3 g 0.2 mole) and phenol (22.0 g 0.234 mole) were charged into a nickel autoclave (capacity 500 ml). Hydrogen fluoride (150 g) was condensed into the autoclave which was then sealed and heated to 75"C for 6 hours.

The hydrogen fluoride was then allowed to evaporate and the product was poured into crushed ice. The crude wet product was stirred with water (500 ml) at 95"C for 1.5 hours and was then collected and dried under vacuum at 90"C. The yield was 45.5 g (97.8% theoretical).

This crude product was dissolved in aqueous 10% by weight potassium hydroxide (250 ml). sodium dithionite (1.5 g) was added and the mixture heated to 75"C. Norit (1 g, decolourising charcoal) and Celite (1 g, diatomaceous earth filtration aid) were added and the suspension filtered (the words "Norit" and "Celite" are registered Trade Marks). The filtrate was poured into hot acetic acid (50 ml) and finally cold water (250 ml) was added.

The crystalline product was collected. dissolved in methylated spirit, treated again with Norit and allowed to crvstallise after the addition of some water.

The pale buff crvstals (melting point 178.5 to 180.5"C) were collected and dried in vacuo at 12ü C. The vield was 34.8 g (74.8ec overall). Assay by titration with ethanolic potassium hydroxide indicated 99.6cm by weight purity.

Examples 2 to 7 Example 1 was repeated using 4-fluorobenzoic acid in place of 4-chlorobenzoic acid and various temperatures and reaction times. The proportions of reactants were as set out in Table 1.

Reactant Molar % 2,4' isomer Crude Example Temp Time Ratios in crude Product "C (hrs) Acid:Phenol:HF product Colour 2 75 6 1:1 : 37.5 1.9 Orange 3 50 " 1:0.95 : 37.5 3.0 Pale orange 4 75 D " 1.9 Orange 5* 5 2 rr 5.2 Orange 6 100 " " 1.5 Brown 7 " 1 D 1.6 Pale orange * No stirring in Example 5.

Mass spectroscopy on the products from Examples 2, 3 and 7 showed only fluorohydroxybenzophenones.

The yields of crude product were about 90% in all the Examples.

After the work-up of dithionite treatment and charcoal followed by recrystallisation the colouration of the crude product was removed and the 2,4'-isomer content was reduced.

WHAT WE CLAIM IS: 1. A process for the manufacture of halophenols of formula

where X = halogen comprising condensing a halo-substituted benzoic acid or acid halide derivative thereof of formula

where Z = OH or halogen, with phenol in the presence of a molar excess of liquid anhydrous hydrogen fluoride.

2. A process according to claim 1 in which Z is -OH.

3. A process according to claim 1 or claim 2 in which the halogen atom X is ortho or para to the -CO- group.

4. A process according to claim 3 in which the halogen atom X is para to the -COgroup.

5. A process according to any one of claims 1 to 4 in which X is selected from chlorine, fluorine, or bromine.

6. A process according to claim 5 wherein X is fluorine and the fluoro compound

is made in situ by reaction of the compound

with a molar excess of an alkali metal nitrite in the presence of at least one mole of liquid anhydrous hydrogen fluoride.

7. A process according to claim 6 in which the alkali metal nitrite is sodium nitrite.

8. A process according to any one of claims 1 to 7 in which the reaction is performed at temperatures of 20-100 C.

9. A process for the preparation of 4-fluoro-4'-hydroxybenzophenone comprising reacting p-aminobenzoic acid, with a molar excess of phenol and of an alkali metal nitrite in the presence of at least two moles of liquid anhydrous hydrogen fluoride.

10. A process according to claim 1 substantially as hereinbefore described and with particular reference to the Example.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Examples 2 to 7 Example 1 was repeated using 4-fluorobenzoic acid in place of 4-chlorobenzoic acid and various temperatures and reaction times. The proportions of reactants were as set out in Table 1. Reactant Molar % 2,4' isomer Crude Example Temp Time Ratios in crude Product "C (hrs) Acid:Phenol:HF product Colour 2 75 6 1:1 : 37.5 1.9 Orange 3 50 " 1:0.95 : 37.5 3.0 Pale orange 4 75 D " 1.9 Orange 5* 5 2 rr 5.2 Orange 6 100 " " 1.5 Brown 7 " 1 D 1.6 Pale orange * No stirring in Example 5. Mass spectroscopy on the products from Examples 2, 3 and 7 showed only fluorohydroxybenzophenones. The yields of crude product were about 90% in all the Examples. After the work-up of dithionite treatment and charcoal followed by recrystallisation the colouration of the crude product was removed and the 2,4'-isomer content was reduced. WHAT WE CLAIM IS:

1. A process for the manufacture of halophenols of formula

2. A process according to claim 1 in which Z is -OH.

6. A process according to claim 5 wherein X is fluorine and the fluoro compound

is made in situ by reaction of the compound

11. Halophenols whenever prepared by a process as claimed in any one of claims 1 to 10.