Q84. - Organic Chemistry

Question

Question: Use the principles of resonance theory to explain why carbocation A is more stable than carbocation B.

                                                      

Step-by-Step Solution

Answer

Answer

Carbocation A is more stable than carbocation B as the positive charge is distributed over the two carbons because of resonance.

Step-by-Step Solution Step 1: Resonance theory

Resonance theory is a theory in which a molecule is shown by several structures instead of a single valence-bond structure. 

A resonance hybrid is also acquired while illustrating various resonance structures.

Step 2: Comparison of carbocations A and B

Structure A comprises one double bond in conjugation with the positive charge. The carbocation B does not possess a double bond. The concept of resonance stabilization can be applied only to structure A. 

The electron density in structure A can be shifted as follows:

                                       

                                         Resonance stabilization in carbocation A

In structure B, the double bond is absent, and the resonance phenomenon does not occur. Hence, carbocation A will be more stable than carbocation B.