Question

What are B and C respectively in the given sequence of reactions?

• A. Cyclohexanol, Cyclohexylmethanol
• B. Cyclohexane, Cyclohexylmethanol
• C. Cyclohexane, Cyclohexylethane
• D. Ethoxycyclohexane, Cyclohexylmethanol

Hint:

Grignard reagents will always prioritize acting as a base over acting as a nucleophile if a proton donor (like water, alcohol, or acid) is present in the mixture.

Answer 1

The Correct Option is B

Step 1: Form the Grignard reagent.
Cyclohexyl bromide with Mg in dry ether gives cyclohexylmagnesium bromide (A).
Step 2: Send one portion of A through an acid-base reaction.
Grignard reagents are strong bases, so reacting A with any active-hydrogen source such as an alcohol simply deprotonates it, releasing the alkane B, cyclohexane.
Step 3: Send another portion of A to react with formaldehyde.
Here the Grignard carbon adds across the carbonyl of HCHO, and acidic workup ($\text{H}_3\text{O}^+$) then delivers a primary alcohol.
Step 4: Identify that alcohol.
Since the new carbon comes from formaldehyde, the product is the cyclohexane ring bearing a $-\text{CH}_2\text{OH}$ arm, cyclohexylmethanol (C).
Final answer: Option 2, Cyclohexane, Cyclohexylmethanol.