Which of the following is most stable?
R−⊕C|R−R is most stable.
Recall: I-effect and hyperconjugation
If you have not read about it, then wait it will come.
Now, let's see how it affects stability.
Stability of carbocations:
The stability of a charged species is increased by the dispersal of charge. Therefore, any factor which tends to spread out the positive charge of −e - deficient C atom and distribute it over the rest of the ion stabilizes the carboaction.
An alkyl group has an −e - donating inductive effect, which tends to release −e's towards the C atom bearing positive charge. In doing so, it reduces positive charge on the C atom. In other words the positive charge gets dispersed as the alkyl group becomes partially positive charged.The more number of alkyl groups, the greater the dispersal of positive charge, and the more stable is the carbocation. Thus, carbocation is stabilized by −e - donating substituents and is destabilized by −e - withdrawing substituents.
We know that the stability of carbonium ions is in the order: 3∘ > 2∘ > 1∘ > CH3 . This is due to a decrease in hyper-conjugative satbilization in the order.