Homolytic and Heterolytic fission

Homolytic and Heterolytic fission:

Bond fission is the process of breaking covalent bonds present in organic molecules. It occurs in the following two ways

Homolytic fission:

Bond fission occurs symmetrically, and shared electrons between two elements are equally distributed between them to form atoms or free radicals.

Heterolytic fission: 

Bond fission occurs unsymmetrically, and shared electrons between two elements are not equally distributed between them. This fission results in the formation of 

1.  Electrophiles
2. Nucleophiles

Electrophiles:

Electrophiles are electron-deficient species that have a tendency to take up electrons, and therefore, they act as Lewis acids.

These are of the following types:

Positively Charged Electrophiles :

H⁺, X⁺ , R⁺, NO₂⁺, NO⁺, SO₃H⁺.

Neutral electrophiles:

These are of the following types:

Neutral electrophiles with an incomplete octet state have a central atom that is electron deficient, that is, it does not have an octet state.
For example, BeX₂, ZnCl₂, BH₃, BX₃, AlX₃, FeX₂

Neutral electrophiles with an extended octet state have a central atom with a vacant d-orbital, which can extend its octet state. For example, SnCl₄, PCl5, IF₇

Nucleophiles:

Nucleophiles are species that have lone pairs of electrons, available for donation, and therefore, they act as Lewis bases.

These are of the following types:

Negatively charged:

H^–, OH^–, R ^–, O^–, CH₃⁻, X^–, SH^–, R^–, S^–.

Neutral:

The central atom with lone pair of electrons to donate. For example,
NH₃  (RNH₂,  etc.)
O (H₂O, HOR, R – O – R)
S (R–SH, R– S– R, H₂S)

Ambidentate nucleophiles

They have two nucleophilic centers, one of which is negatively charged and the other one is neutral.
For example, C≡N, O−N=O, NO₂

 

 

 

 

 

 

 

 

 

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