Reaction #742281

Reaction equation

NaNO2

6-aminonaphthalene-2-sulfonic acid

NaOH

SnCl2

H2SO4

→

6-hydrazinylnaphthalene-2-sulfonic acid

Yield 77.2%

Solvents

H2O

HCl

H2O

H2O

H2O

Conditions

Workup

1. 1
   workup.STIRRINGAfter the solution was stirred at 0° C. for 2 h
2. 2
   Otherthe diazonium salt was removed by filtration
3. 3
   Washwashed with cold water
4. 4
   workup.STIRRINGThe mixture was stirred overnight
5. 5
   FiltrationThe solid was filtered
6. 6
   Washwashed twice with water
7. 7
   Otherdried under vacuum

Procedure

To a solution of 6-aminonaphthalene-2-sulfonic acid (2.23 g, 10 mmol) in 15 ml of H2O was added 2N NaOH (0.75 ml). The mixture was stirred for 5 min at RT and conc. H2SO4 (0.68 g, 6.9 mmol) was added to it dropwise at 0° C. 2 ml of iced H2O was added, followed by a solution of NaNO2 (1.04 g, 15 mmol) in 2 ml of H2O. After the solution was stirred at 0° C. for 2 h, the diazonium salt was removed by filtration and washed with cold water. The salt was then added in portions to a cold (<0° C.) solution of SnCl2 (4.9 g, 22 mmol) in 3.2 ml of conc. HCl and 1.8 ml of H2O. The mixture was stirred overnight. The solid was filtered and washed twice with water, dried under vacuum to give 1.84 g of 6-hydrazinylnaphthalene-2-sulfonic acid (77%), which was used directly for next step.

Source