Question

What is the purpose of adding the NaOH and H2O in step 1, and the HCl in step 4?

SYNT 730 Dyeing: (with Orange II and Para-Red) HO -N=N Orange lI Para-Red Procedure I. Prepare two 100 mL beakers: to each add 25 mL 10% NaOH and 25 mL H2O. 2. Add 100 mg of Orange II to one beaker and 100 mg of Para-Red to another beaker. 3. Heat each beaker to boiling then add a cotton strip to each beaker. Boil for 2 min. 4. Prepare two more beakers: to each add 50 mL H2O then 6 mL conc. HCI 5. Place the Orange II dyed cotton strip in one HCl beaker and Para-Red dyed cotton in the other. Let each stand for 2 min. 6. Rinse each strip in running water. Let dry. Admire

Answer 1

The mechanism shown was an aromatic addition-elimination mechanism, where the strong electron-withdrawing groups (sulfonate and nitro) can well stabilize the negative charge at ipso-position and gives the corresponding products.

Purpose of adding NaoH and water Purpose of adding Hcl: N_2 + 8Hcl rightarrow 2NH_4 cl + 3cl_2 To cool the nitrogen gas obtained and convert to NH_4 cl (neutral).