Question

The Maximum number of RBr producing 2-methylbutane by above sequence of reaction

• A. 3
• B. 5
• C. 4
• D. 6

Hint:

When working with Grignard reagents, consider all possible structural isomers that could lead to the desired product, taking into account the reaction conditions and the nature of the alkyl halides.

Answer 1

The Correct Option is A

Step 1: Identify possible alkyl groups with four carbon atoms.
The alkyl portion (R) of butyl groups (C₄H₉–) can be arranged in four distinct structural isomers:

1. n-Butyl bromide \[ CH_3 - CH_2 - CH_2 - CH_2Br \]
2. sec-Butyl bromide \[ CH_3 - CHBr - CH_2 - CH_3 \]
3. iso-Butyl bromide \[ (CH_3)_2CH - CH_2Br \]
4. tert-Butyl bromide \[ (C H_3)_3CBr \]

Each isomer exhibits a unique atomic configuration, resulting in distinct structures and physical properties.

---

Step 2: Determine the total count of feasible structures.

\[ \boxed{\text{Total distinct structures for } RBr = 4} \]

---

Final Answer:

\[ \boxed{4 \text{ distinct isomeric structures for } RBr \text{ (C}_4H_9Br)}} \]

---

Key Principle:

The number of structural isomers for alkyl halides (R–X) directly corresponds to the number of structural isomers of the alkyl group (R). For butyl bromide, these are n-butyl bromide, sec-butyl bromide, iso-butyl bromide, and tert-butyl bromide.