# What is the most stable carbocation?

Feb 28, 2015

The tricyclopropropylcyclopropenium cation is the most stable carbocation.

#### Explanation:

1° < 2° < 3°

We know that the stability order of aliphatic cations is

Resonance Stabilization

Neighboring double bonds are better stabilizers, because they can donate electrons by resonance.

Hence, the triphenylmethyl cation, ("C"_6"H"_5)_3"C"^"+" is stable because it has many resonance structures.

However, the resonance overlap of the π orbitals is not perfect because steric hindrance forces the ion to have a propeller shape.

Tricyclopropylmethyl

More stable is the tricyclopropylmethyl cation.

The bent bonds of the cyclopropane ring can overlap with the empty $\text{p}$ orbital without steric hindrance.