In the 3 diazo reagents setup, what is Diazo B composition?

• A. 0.5% sodium nitrite
• B. 0.1% sulfanilic acid
• C. 1.5% HCl
• D. 50% methanol

Answer: (A)

In this three-diazo reagents setup, forming the diazonium intermediate requires nitrous acid, which is generated from nitrite. One reagent provides the amine that will be diazotized, another supplies the nitrite to form the diazonium ion, and the third sets the acidic/coupling environment. Therefore, the component that serves as the nitrite source is the sodium nitrite solution. That’s why 0.5% sodium nitrite is the correct composition for the second diazo reagent. The other options correspond to the diazotizing amine (sulfanilic acid), the acid needed for the reaction, or the solvent, not the nitrite source.