Question

Choose the correct options regarding $A,B,C,DandE$ ?

• A. A contains $-Br$.
• B. B and D are grignard reagents.
• C. C contains $-OH$.
• D. E contains only one five membered ring.

Answer 1

Answer: (A), (B)

A contains $-Br$.
B and D are grignard reagents.

Answer: options A and B are correct.
Explanation:
The four reactions (marked as 1, 2, 3 , and 4 in the image below) can be explained as follows:
Reaction (1): Phosphorus tribromide reacts with cyclopentyl alcohol to replace alcoholic-OH with a bromine atom, forming cyclopentyl bromide (A). Thus, option A is correct.
Reaction (2): cyclopentyl bromide (A) reacts with Mg in presence of ether to form Grignard reagent, cyclopentyl magnesium bromide (B). Thus, option B is correct.
Reaction (3): CrO3/CH3COOH forms chromic acid that oxidizes cyclopentyl alcohol, which is a secondary alcohol to corresponding ketone i.e., cyclopentyl ketone (C). Thus, option C is wrong.
Reaction (4): cyclopentyl ketone (C) reacts with cyclopentyl magnesium bromide, in acidic medium, to form alcohol (E) with two 5-membered cyclopentyl rings. Thus, option D is wrong.