Sulphonation of phenols
View Patent ↗A process for the preparation of sulphonated phenols of general formula (I) where R 1 is hydrogen, a C 1 -C 20 alkyl group which is unsubstituted or substituted by halogen, cyano, hydroxyl, C 1 -C 20 alkoxy, C 2 -C 20 alkoxycarbonyl, acyloxy and/or phenyl which is unsubstituted or substituted by C 1 -C 4 alkyl, C 1 -C 4 alkoxy and/or halogen, R 2 is hydrogen, C 1 -C 20 alkyl or benzoyl of general formula (II) where R 3 and R 4 independently of one another are each hydrogen, halogen, C 1 -C 12 alkyl, C 1 -C 12 alkoxy, C 1 -C 4 haloalkyl, C 3 -C 8 cycloalkyl, C 4 -C 12 cycloalkylalkyl, cyano, hydroxyl, or hydroxyethyl or are each phenoxy, C 7 -C 10 phenylalkyl or phenyl which is unsubstituted or substituted by C 1 -C 4 alkyl, C 1 -C 4 alkoxy and/or halogen, and R 5 is hydrogen or the group SO 3 X where X can be hydrogen, a monovalent metal or a group —N(R 6 ) 3 , where each of the three radicals R 6 can be independently of one another hydrogen, C 1 -C 6 alkyl or C 1 -C 6 hydroxy alkyl, which process comprises reacting a phenol of general formula (III) where R 1 and R 2 are as defined above, with a halosulphonic acid in a solvent which is a mixture of a C 5 -C 10 aliphatic or cycloaliphatic hydrocarbon and a dialkyl carbonate of general formula (IV) R 7 —O—CO—O—R 8 where R 7 and R 8 each represent independently a C 1 -C 4 alkyl group
1. A process for the preparation of sulphonated phenols of the general formula I
where R 1 is hydrogen, a C 1 -C 20 alkyl group which is unsubstituted or substituted by halogen, cyano, hydroxyl, C 1 -C 20 alkoxy, C 2 -C 20 alkoxycarbonyl, acyloxy and/or phenyl which is unsubstituted or substituted by C 1 -C 4 alkyl, C 1 -C 4 alkoxy and/or halogen, R 2 is hydrogen, C 1 -C 20 alkyl or benzoyl of the general formula II
where R 3 and R 4 independently of one another are each hydrogen, halogen, C 1 -C 12 alkyl, C 1 -C 12 alkoxy, C 1 -C 4 haloalkyl, C 3 -C 8 cycloalkyl, C 4 -C 12 cycloalkylalkyl, cyano, hydroxyl, or hydroxyethyl or are each phenoxy, C 7 -C 10 phenylalkyl or phenyl which is unsubstituted or substituted by C 1 -C 4 alkyl, C 1 -C 4 alkoxy and/or halogen, and R 5 is hydrogen or the group SO 3 X where X can be hydrogen, a monovalent metal or a group —N(R 6 ) 3 , where each of the three radicals R 6 can be independently of one another hydrogen, C 1 -C 6 alkyl or C 1 -C 6 hydroxy alkyl which process comprises reacting a phenol of the general formula III
where R 1 and R 2 are as defined above, with a halosulphonic acid in a solvent which is a mixture of a C 5 -C 10 aliphatic or cycloaliphatic hydrocarbon and a dialkyl carbonate of the general formula IV
R 7 —O—CO—O—R 8 IV
where R 7 and R 8 each represent independently a C 1 -C 4 alkyl group.
2. The process of claim 1 wherein the phenol of general formula III is catechol, resorcinol, hydroquinone or a benzophenone.
3. The process of claim 1 wherein the benzophenone is a 4-alkoxy-2-hydroxybenzophenone.
4. The process of claim 1 wherein the halosulphonic acid is chlorosulphonic acid.
5. The process of claim 1 wherein a dialkyl carbonate in the solvent mixture is selected from the group consisting of dimethyl carbonate, diethyl carbonate or diisopropyl carbonate.
6. The process of claim 1 wherein an aliphatic or cycloaliphatic hydrocarbon in the solvent mixture is selected from the group consisting of hexane, cyclohexane, methylcyclohexane, heptane, isooctane, isononane or decane.
7. The process of claim 1 carried out with an excess of the phenol of general formula III over the halosulphonic acid.
8. The process of claim 7 wherein there is provided in the reactants a 2 to 5 mol % excess of the phenol over the halosulphonic acid.
9. The process of claim 1 wherein the concentration of the phenol of general formula III in the solvent mixture is 5 to 50% w/w.
10. The process of claim 9 wherein the concentration of the phenol in the solvent mixture is 15 to 30% w/w.
11. The process of claim 1 wherein the dialkyl carbonate solvent and the aliphatic or cycloaliphatic hydrocarbon solvent are mixed in a weight ratio of from 10:90 to 90:10.
12. The process of claim 11 wherein the weight ratio of the dialkyl carbonate solvent to the aliphatic or cycloaliphatic hydrocarbon solvent is 40:60 to 60:40.
13. The process of claim 1 carried out at a temperature between −10° C. and 80° C.
14. The process of claim 13 wherein the sulphonation reaction is carried out at a temperature between 0° C. to 30° C. and the products of the sulphonation are then raised gradually to 60° C. to 70° C. to remove acid byproduct from the sulphonation reaction.
15. The process of claim 1 carried out at a pressure between 2 mm and 760 mm.
16. The process of claim 2 wherein the halosulphonic acid is chlorosulphonic acid.
17. The process of claim 16 wherein a dialkyl carbonate in the solvent mixture is selected from the group consisting of dimethyl carbonate, diethyl carbonate or diisopropyl carbonate.
18. The process of claim 17 wherein an aliphatic or cycloaliphatic hydrocarbon in the solvent mixture is selected from the group consisting of hexane, cyclohexane, methylcyclohexane, heptane, isooctane, isononane or decane.
19. The process of claim 18 wherein there is present in the reactants an excess of phenol of general formula III over the halosulphonic acid.
20. The process of claim 19 wherein the concentration of the phenol of the general formula III in the solvent mixture is 5 to 50% w/w.