Sulfuric Acid → 4-Hydrazinobenzenesulfonic acid

Temperature

10 °C

Sulfanilic acid (52 g, 0.3 mol) was dissolved in 200 ml H2O containing 16.5 g Na2CO3. The resulting solution was cooled to 10° C. and 35 g of conc. H2SO4 was then added dropwise, followed by the addition of 75 ml 4N NaNO2. The diazotization step was carried out for 15 min at 10°-12° C., then the diazonium salt was collected by filtration, washed with a small amount of cold water and added, at 5° C., to a stirred solution of 85 g of Na2 SO3 in 250 ml H2O. After stirring the reaction mixture for 1 h, the temperature was raised to 95° C. and 240 ml of concentrated H2SO4 was added over a period of 30 min. The reaction mixture was left overnight and the precipitated product was collected, washed with cold water and dried. The phenylhydrazine-4-sulfonic acid obtained (52 g) was dissolved in 500 ml H2O containing 60 ml 30% NaOH, and 30 g (0.28 mol) of benzaldehyde was added at 50°-55° C. Stirring was continued for 1 h, the temperature was reduced to 30° C., and the product was precipitated by acidification with 36 ml 30% HCl. The product was collected, washed with a small amount of cold water and dried, to give 50 g of benzaldehyde phenylhydrazone-4-sulfonic acid.

1. filtrationthe diazonium salt was collected by filtration
2. washwashed with a small amount of cold water
3. additionadded, at 5° C., to a stirred solution of 85 g of Na2 SO3 in 250 ml H2O
4. temperaturethe temperature was raised to 95° C.
5. addition240 ml of concentrated H2SO4 was added over a period of 30 min
6. waitThe reaction mixture was left overnight
7. customthe precipitated product was collected
8. washwashed with cold water
9. customdried

ORD record

ord-d43f351e28bf490f91004c1bffbf1b15

Source dataset

uspto-grants-1997_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05677434