Benzoic Acid → 2-Phenylbenzimidazole-5-sulfonic acid

HRID 2259427Notes

Reaction equation

HRID 2259427 reaction equation
[S:1](=[O:5])(=O)([OH:3])[OH:2].[C:6]1([NH2:13])[CH:11]=[CH:10][CH:9]=[CH:8][C:7]=1[NH2:12].[C:14](O)(=O)[C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1>O>[C:15]1([C:14]2[NH:12][C:7]3[CH:8]=[C:9]([S:1]([OH:3])(=[O:5])=[O:2])[CH:10]=[CH:11][C:6]=3[N:13]=2)[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1

Participants

5

Reactant 3

HCID 243Benzoic Acid2×HCID 1118Sulfuric AcidHCID 7243O-Phenylenediamine

Product 1

HCID 339192-Phenylbenzimidazole-5-sulfonic acidYield 49%

Reagents, catalysts & solvents 1

HCID 962WaterSolvent

Conditions

Temperature
200 °C

Procedure

A 1 1 three-necked flask is initially charged with 275 g (2.70 mol) of 96% sulfuric acid and subsequently 54.1 g (0.50 mol) of 1,2-phenylenediamine are carefully introduced. 85.5 g (0.70 mol) of benzoic acid are added to the suspension, which at this point has a temperature of about 120° C., and the mixture is heated while stirring (clear solution from about 130° C.) to about 200° C. for 5 hours, during which a small proportion of the benzoic acid sublimes. The mixture is then allowed to cool to about 150° C. and is stirred into 1 l of cold water, which warms to about 65° C. The mixture is stirred for a further hour at 65° C. and the precipitate is then filtered off with suction and washed with water at a temperature of 80° C. until free of sulfate. The dried crude product (83 g) is suspended in 830 ml of water and the pH is adjusted to 8 with 32% sodium hydroxide solution. After addition of 6.5 g of activated carbon the mixture is stirred for a further 30 minutes at room temperature and subsequently clarified by filtration. The filtrate is heated to 80° C. and the pH is adjusted to 3 with concentrated hydrochloric acid. The precipitated Eusolex 232 is filtered off with suction while warm, washed with 2 l of water at a temperature of 90° C. and dried to constant weight in a vacuum drying cabinet at 75° C. and 20 mbar. 67.0 g (245 mmol, 49% of theory) of 2-phenylbenzimidazole-5-sulfonic acid are obtained, 410° C. (decomposition).

Workup

  1. additionare carefully introduced
  2. customa temperature of about 120° C.
  3. temperaturethe mixture is heated
  4. temperatureto cool to about 150° C.
  5. customwarms to about 65° C
  6. stirringThe mixture is stirred for a further hour at 65° C.
  7. filtrationthe precipitate is then filtered off with suction
  8. washwashed with water at a temperature of 80° C. until free of sulfate
  9. dry with materialThe dried crude product (83 g)
  10. additionAfter addition of 6.5 g of activated carbon the mixture
  11. stirringis stirred for a further 30 minutes at room temperature
  12. filtrationsubsequently clarified by filtration
  13. temperatureThe filtrate is heated to 80° C.
  14. filtrationThe precipitated Eusolex 232 is filtered off with suction
  15. temperaturewhile warm
  16. washwashed with 2 l of water at a temperature of 90° C.
  17. customdried to constant weight in a vacuum
  18. customdrying cabinet at 75° C.

Sources & evidence

ORD record
ord-e53ef5dc577f483d977d78cfdc34d279
Source dataset
uspto-grants-1995_12
Patent number
US05473079

Reaction notes

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