Starting with pure, unsubstituted benzene, a chemist performs the following flawless synthetic sequence: 1) Nitration () 2) Bromination () 3) Reduction () 4) Diazotization () 5) Balz-Schiemann reactio

Question

Starting with pure, unsubstituted benzene, a chemist performs the following flawless synthetic sequence:
1) Nitration ($HNO_3/H_2SO_4$)
2) Bromination ($Br_2/Fe$)
3) Reduction ($Sn/HCl$)
4) Diazotization ($NaNO_2/HCl, 0^\circ C$)
5) Balz-Schiemann reaction ($HBF_4$, heat).
What is the mathematical sum of the numerical locants assigned strictly to the halogen substituents in the correct IUPAC name of the final isolated major product?

Prashant Kotian · Accepted Answer

Correct answer: 4. Step 1 yields nitrobenzene. Step 2 introduces a bromine atom. Because the group is strongly meta-directing, the product is -bromonitrobenzene. Step 3 reduces the nitro group to an amine, yielding -bromoaniline. Step 4 converts the amine to a diazonium salt, yielding -bromobenzenediazonium chloride. Step 5 replaces the diazonium group with fluorine. The final molecule contains a bromine and a fluorine atom in a meta relationship. Alphabetically, bromo comes before fluoro, so it is named 1-bromo-3-fluorobenzene. The sum of the halogen locants is .

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