Question

What is the relative stabilities order of the given compounds?

• A. $4<2<3<1$
• B. $2<4<3<1$
• C. $4<2<1<3$
• D. $2<4<1<3$

Answer 1

Answer: (A)

$4<2<3<1$

Due to the presence of phenyl group the stabilities of the carbocations $1,2$ and $3$ are greater than cation $4$, (due to resonance). Further, the presence of electron-donating groups on the phenyl ring increases the stability of carbocation.
Hence, cation $1$ and $3$ are more stable than cation $2$. Moreover $-OMe$ group shows $+M$ effect which is more prominent than $+l$ effect of $-$Me group. Thus, cation $1$ is more stable than cation $3$. So, the correct order is, $4<2<3<1$.