[figure] Consider the above sequence of reactions. The number of bromine atom(s) in the final product (P) will be :
- 6
- 5
- 1
- 3
Answer
(2) 5
Solution
Step (1): –NO2 is a deactivating, meta-directing group m-bromonitrobenzene.
[figure]
Steps (2), (3): Sn/HCl reduces –NO2 to –NH3+ (anilinium salt); neutralisation frees the amine m-bromoaniline.
[figure]
Step (4): –NH2 is strongly activating and o/p-directing; bromine water substitutes all free o- and p-positions (2, 4, 6) 2,3,4,6-tetrabromoaniline.
[figure]
Steps (5), (6): diazotisation gives the diazonium salt ArN2 Br ; Sandmeyer reaction (CuBr) replaces – N2 by –Br pentabromobenzene.
[figure]
P (C6HBr5) contains 5 bromine atoms.
Answer: (2)