Question

An organic compound (X) with molecular formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ is not readily oxidised. On reduction it gives $\left(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}(\mathrm{Y})\right.$ which reacts with HBr to give a bromide (Z) which is converted to Grignard reagent. This Grignard reagent on reaction with (X) followed by hydrolysis give 2,3-dimethylbutan-2-ol. Compounds (X), (Y) and (Z) respectively are:

• A. $\mathrm{CH}_{3} \mathrm{COCH}_{3}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{3}$
• B. $\mathrm{CH}_{3} \mathrm{COCH}_{3}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{3}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{3}$
• C. $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}$
• D. $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO}, \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{3}$

Hint:

Follow the reaction sequence to identify the compounds involved.

Answer 1

The Correct Option is B

The problem involves identifying the correct organic compounds (X), (Y), and (Z) based on their chemical behaviors and structural transformations. Let's solve this step-by-step:

1. Compound (X) has the molecular formula \(\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}\) and is not readily oxidized. A common compound with this molecular formula is acetone (propanone), which is a ketone. Ketones generally resist oxidation under mild conditions.
2. Upon reduction, compound (X) gives compound (Y) with the formula \(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}\). A viable reduction product of acetone is isopropanol (2-propanol) because ketones reduce to secondary alcohols.
3. Compound (Y), i.e., isopropanol, reacts with HBr to form compound (Z). This reaction is characteristic of alcohols converting to alkyl halides, thus forming isopropyl bromide (2-bromopropane).
4. This compound (Z), isopropyl bromide, is converted into a Grignard reagent. When reacted with a ketone like acetone (compound X), followed by hydrolysis, Grignard reagents typically add to the carbonyl group. Thus, the formation of the tertiary alcohol, 2,3-dimethylbutan-2-ol, confirms the interactions.

Based on the above reasoning, the correct identities are:

• Compound (X): Acetone (\(\mathrm{CH}_{3} \mathrm{COCH}_{3}\))
• Compound (Y): Isopropanol (2-propanol, \(\mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{3}\))
• Compound (Z): Isopropyl bromide (2-bromopropane, \(\mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{3}\))

Thus, the correct option is

$\mathrm{CH}_{3} \mathrm{COCH}_{3}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{3}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{3}$

Answer 2

1. Compound (X): - $\mathrm{CH}_{3} \mathrm{COCH}_{3}$ (Acetone) 
2. Reduction to (Y): - $\mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{3}$ (Isopropyl alcohol) 
3. Reaction with HBr to form (Z): - $\mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{3}$ (2-Bromopropane) 
4. Grignard reagent and reaction with (X): - The Grignard reagent formed from (Z) reacts with acetone to form 2,3-dimethylbutan-2-ol after hydrolysis. 
Therefore, the correct answer is (2) $\mathrm{CH}_{3} \mathrm{COCH}_{3}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{3}, \mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{3}$.