Question

Among the following species, the most stable carbonium ion is

• A. C\(_6\)H\(_5\)CHC\(_6\)H\(_5^+\)
• B. C\(_6\)H\(_5\)CH\(_2^+\)
• C. CH\(_3\)CH\(_2^+\)
• D. C\(_6\)H\(_5\)CH\(_2\)CH\(_2^+\)

Hint:

Resonance stabilization is the most significant factor in carbocation stability. The more resonance structures possible, the more stable the carbocation.

Answer 1

The Correct Option is A

To determine which species among the given options is the most stable carbonium ion, we consider the stability of carbocations, which typically depends on factors such as inductive effect, hyperconjugation, and resonance. Let's analyze each option:

\(C_6H_5CHC_6H_5^+:\) This is a diphenylmethyl cation. It has significant stabilization due to resonance, as the positive charge can be delocalized over two phenyl rings. This delocalization of charge provides substantial stability, making it more stable than other options.

\(C_6H_5CH_2^+:\) This is a benzyl cation, which is stabilized by resonance, but less than the diphenylmethyl cation. The positive charge can resonate with only one phenyl group.

\(CH_3CH_2^+:\) This is an ethyl cation. It is primarily stabilized by hyperconjugation and the inductive effect, but lacks the extra resonance stabilization present in the cations with aryl groups.

\(C_6H_5CH_2CH_2^+:\) This is a phenethyl cation. Similar to the ethyl cation, it has some stabilization by hyperconjugation and slightly by resonance, but is less stable than diphenylmethyl and benzyl cations due to the reduced effective resonance.

Based on the above analysis, the \(C_6H_5CHC_6H_5^+\) ion is the most stable due to its ability to delocalize the positive charge over two phenyl rings through resonance. Therefore, the correct answer is:

C₆H₅CHC₆H₅⁺