Propionic acid with Br2/P yields a dibromo product. Its structure would be
- [figure]
- CH2(Br)-CH2-COBr
- [figure]
- CH2(Br)-CH(Br)-COOH
Answer
(3) [figure]
Solution
As per NCERT, carboxylic acids having α-hydrogens are halogenated at the α-position on treatment with X2 in the presence of red phosphorus (Hell–Volhard–Zelinsky reaction).
Propionic acid CH3CH2COOH has two α-hydrogens; both are replaced:
CH3CH2COOH Br2/P CH3CHBrCOOH Br2/P CH3CBr2COOH
The dibromo product is 2,2-dibromopropanoic acid.
Answer: (3)