About the substitution reaction

[vicki]

for carbanions, for carbocations and for carbon-centred radicals, does increasing the number of alkyl substituents stabilise or destabilise the intermediate? and why so?

 

[so-crates]

What effect would increasing the number or substituents have on the charge distribution for the ions and the radical?

 

[ravenprp]

The number of alkyl substituents can have a significant impact on the stability of carbanions, carbocations, and carbon-centred radicals in substitution reactions. Generally, increasing the number of alkyl substituents on these intermediates will stabilize them, making them less reactive and more likely to participate in the desired substitution reaction.

This is due to the inductive effect of alkyl groups. Alkyl groups are electron-donating and can help stabilize the negative charge on carbanions and the positive charge on carbocations. This is because the alkyl groups can donate some of their electron density to the intermediate, reducing the overall charge and making it more stable.

On the other hand, if there are too many alkyl groups attached to the intermediate, it can lead to steric hindrance. This occurs when the bulky alkyl groups get in the way of the reaction, making it difficult for the intermediate to interact with the reactants. This can decrease the reactivity of the intermediate and slow down the overall reaction.

In the case of carbon-centred radicals, increasing the number of alkyl substituents can also stabilize the intermediate. This is because the alkyl groups can help delocalize the unpaired electron and distribute the charge, making the radical more stable and less reactive.

In summary, increasing the number of alkyl substituents can generally stabilize carbanions, carbocations, and carbon-centred radicals in substitution reactions. However, there is a point where too many alkyl groups can lead to steric hindrance and decrease the reactivity of the intermediate.