[[V]]

Is it safe to say that the factors that stabilize a free radical are equivalent to the factors that stabilize a carbocation? And the factors that stabilize an anion are inverse to those that stabilize its cation? Therefore the factors that stabilize an anion are exact opposite to those that stabilize a radical?

(In all these examples we are using the same atom [carbon]).

The reason why I believe radicals behave the same way as carbocations is because now the p-orbital they occupy are both S+ or partially S+.

So far from what I understand, they follow the same trends with hyperconjucation & induction, resonance, etc.

Can someone confirm or deny this? Please point out some specific weaknesses in my understanding!

Thank you

[Honclbrif]

The way I've always thought of it is that both carbocations and carbon radicals are electron deficient because neither have a filled octet, so electron donating groups will tend to stabilize both.

[[V]]

Thank you. Can you please explain this trend?

Bond disassociation energies.
CH3-X  kcal/mol
CH3-F  108
CH3-Cl 83.5
CH3-Br 70
CH3-I  56

As atom size increases, BDE decreases. This means as the radius increases, the stability of a radical on the halogen also increases. Anion stability increases as the atom size gets bigger. I am assuming cations are destabilized when EN is held fairly constant, but radius is increased, right? So why does this not apply to radical formation? (The reason why I think + charges are destabilized by larger radius, is because larger radius = larger positive charged mass to circulate).

[Telamond]

BDE is measured as the energy for the homolytic cleavage.
So for CH3-X -> CH3^. + X^.

The way I see it; the lower down the period you go, the more difference in size the orbitals will be, and the orbital overlap will decrease, creating weaker bonds. This makes the bond easier to cleave.

[[V]]

Yes, and dosnt the amount of energy required to cleave the bond correlate directly to how stable the radicals formed would be? How does atomic size stabilize/destabilize a radical?

[[V]]

Does an increase in atomic radius stabilize both negative charges AND positive charges?

[Kadabrium]

theoreotically is but since the negative nuclear charge is also disconcentrated .. large cations are ofcourse stable but anions may not. also for a simple CH3X a ionic model is equivalent to a radical model i suppose, for ionic strength for F-is greater than I- but dissociated radical stability I- greater than f-