free Radical


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Reaction Intermediates

Short lived fragments obtained by homolytic & hetrolytic fission are called Reaction intermediates.  The important reaction intermediates are free redicals, carbonium ion & carbanions.


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Free Radical

A free radical may be defined as an atom or group of atoms having an odd or unpaired election. These are obtained by the homolytic fission of covalent bond . Free radicals are denoted by putting a dot (.) against the symbol of atom or group of atoms.


The formation of free radical is initiated by heat, light or catalyst.

 Free Radical : Characteristics 

1)  Free radicals are electrically neutral.

2) They are highly unstable.

3) They are highly reactive due to presence of odd electrons. In methyl free radical 7 electrons are present on its carbon . They readily try to pair up the unpaired electron.

4) Free radicals are para magnetic is nature.

5) Normally free radicals are formed in the presence of sunlight & when the reactants are in gaseous state.

6) The stability order of free radicals are as follows-

Benzyl > Allyl > Tertiary >secondary >Primary

7) It shows sp2 hybridisation



Difference between free radicals & ions


Free radical ions
1. These are neutral in nature.

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1. They carry either positive or negative charge.

Example :


2. One unpaired electron is present in valence shell. 2. Paired electrons are present in valence shell.
3. They are para magnetic in nature. 3. They are dia magnetic in nature,
4. These are formed by homolytic fission of covalent bond. 4. These are formed by heterolytic fission of covalent bond.