Singlet state:
Substituents that can donate electron pair stabilize singlet state by delocalizing the electron pair into empty p orbital.
CF2>CH2>CCl2
CH2 there are no -I groups as such so it is relatively stable.
Both Cl and F are electron withdrawing groups but, in case of CF2 there are 2 effects operating the inductive effect and the backbonding. In case of -F it has lone pairs in the similar 2p orbitals as cabon and so the backbonding is much more effective. Though backbonding is there it is only an additional effect so CH2 is more stable.
In CCl2 the backbonding is very low so it is least stable n moreover it is an electron withdrawing group..
Moderation Team
![[Post New]](/templates/default/images/icon_minipost_new.gif){kind=icon}
![[Up]](/templates/default/images/icon_up.gif "[Up]"){kind=icon}
253
