Question

The stability of $1^{\circ }$, $2^{\circ }$, $3^{\circ }$ carbocation and benzyl carbocations is of the order :

• A. $1^{\circ }>2^{\circ }>3^{\circ }>benzyl$
• B. Benzyl >$3^{\circ }>2^{\circ }>1^{\circ }$
• C. $3^{\circ }>2^{\circ }>1^{\circ }>benzyl$
• D. $3^{\circ }>benzyl>2^{\circ }>1^{\circ }$

Answer 1

The correct option is B Benzyl >$3^{\circ }>2^{\circ }>1^{\circ }$

Carbocations are stabilized by nearby electron-donating groups. The stability of carbocations increases as we go from primary to secondary to tertiary carbons. Because of hyperconjugation, which invokes stabilization through donation of the electrons in C-H sigma bonds to the empty p orbital of the carbocation. Benzyl carbocation is most stable because of delocalization of charge due to resonance of $\pi$ electrons in the ring. The order is $Benzyl>3^o>2^o>1^o$