Question

The correct statement about the product of the following reaction is: 
\[ \text{CH}_3\text{CHO} \xrightarrow{(i)\ \text{C}_2\text{H}_5\text{MgBr}} \xrightarrow{(ii)\ \text{H}_2\text{O}} \text{product} \]

• A. It undergoes dehydration with 20% H$_3$PO$_4$ at 358 K
• B. It gives ketone on oxidation with CrO$_3$
• C. It does not give positive iodoform test
• D. It is a vinylic alcohol

Hint:

Grignard reagents add to carbonyl groups to form alcohols. Secondary alcohols yield ketones upon oxidation.

Answer 1

The Correct Option is B

Step 1: Grignard reaction mechanism. Grignard reagent (C$_2$H$_5$MgBr) reacts with an aldehyde (CH$_3$CHO) to give a secondary alcohol after hydrolysis: \[ \text{CH}_3\text{CHO} + \text{C}_2\text{H}_5\text{MgBr} \xrightarrow{\text{H}_2\text{O}} \text{CH}_3\text{CH(OH)CH}_2\text{CH}_3 \] This is butan-2-ol (a secondary alcohol). 
Step 2: Oxidation of secondary alcohol. Butan-2-ol on oxidation with CrO$_3$ gives a ketone — butan-2-one. 
Conclusion: The correct statement is that the product gives a ketone on oxidation with CrO$_3$.