Question

In reference to carbocations, what do we mean by stability? Are not all carbocations high energy species?

Answer 1

Because when we talk of stability, we mean relative stability.

Explanation:

For formation of the carbocation, we could represent its formation this way:

`R-X rightleftharpoonsR^(+) + X^-`

A carbon-halogen bond is broken whatever the identity of the `R` group, and the reactive species, the `R^+` carbocation, might have a transient existence, microseconds to milliseconds, depending on solvent, temperature, and concentration. Nevertheless, its lifetime is prolonged in the case of substituents which stabilize the positive charge, and thus reactivity tends to proceed thru this route.

On the other hand, methyl carbocation, with zero stabilization possible, is a high energy species, which would require very forcing conditions.