Question

Identify the major product formed from the following reaction sequence

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Secondary alcohols give ketones on dehydrogenation with \(Cu/573\,K\). Acetone undergoes aldol condensation followed by dehydration to form mesityl oxide.

Answer 1

The Correct Option is D

Step 1: Addition of HBr to propene.
The starting compound is propene: \[ CH_3-CH=CH_2 \] On reaction with \[ HBr \] it follows Markovnikov addition.
Therefore, bromine attaches to the more substituted carbon and the product formed is: \[ CH_3-CHBr-CH_3 \] This compound is \(2\)-bromopropane.

Step 2: Reaction with aqueous \(NaOH\).
On treatment with \[ NaOH, \] \(2\)-bromopropane undergoes nucleophilic substitution to form propan-\(2\)-ol: \[ CH_3-CHBr-CH_3 \rightarrow CH_3-CHOH-CH_3 \]

Step 3: Dehydrogenation over copper at \(573\,K\).
Secondary alcohols on heating with copper at \[ 573\,K \] undergo dehydrogenation to form ketones.
Thus, propan-\(2\)-ol gives acetone: \[ CH_3-CHOH-CH_3 \xrightarrow{Cu/573\,K} CH_3COCH_3 \]

Step 4: Condensation of acetone with \(Ba(OH)_2\) and heat.
Acetone undergoes aldol condensation in the presence of \[ Ba(OH)_2 \] followed by dehydration on heating.
The major product formed is mesityl oxide: \[ CH_3COCH_3 \xrightarrow{Ba(OH)_2,\Delta} CH_3COCH=C(CH_3)_2 \]

Step 5: Final conclusion.
Therefore, the major product is \[ \boxed{\text{Mesityl oxide}} \]