Question

Find the number of hyperconjugation structures in the isopropyl carbocation.

• A. \(3\)
• B. \(6\)
• C. \(9\)
• D. \(12\)

Hint:

Count the alpha C-H bonds next to the positive carbon.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Hyperconjugation counts the number of \(\alpha\)-hydrogens, i.e. the C-H bonds on carbons next to the positively charged carbon. Each such C-H bond gives one hyperconjugative structure.

Step 2: Detailed Explanation:
The isopropyl cation is \((\text{CH}_3)_2\text{CH}^+\). The cationic carbon is attached to two \(\text{CH}_3\) groups.
Each \(\text{CH}_3\) carries 3 hydrogens, so total \(\alpha\)-hydrogens = \(3 + 3 = 6\).
The \(\text{H}\) on the cationic carbon itself is not an \(\alpha\)-hydrogen.
So there are 6 hyperconjugation structures. The value 3 counts one methyl only, and 9 is for the tert-butyl cation.

Step 3: Final Answer:
Six structures, option (B).

Final Answer:
There are 6 alpha hydrogens, so 6 structures. \[ \boxed{\text{(B) }6} \]