What are free radicals? How are these formed? Discuss the structure of free radicals.

These are such chemical species which have an odd electron or unpaired electron. They have no change are paramagnetic in nature. They are extremely reactive in nature. For example. 
CH₃                                C₂H₅                            C₃H₇
Methyl free radical           Ethyl free radical          Propyl free radical
Formation of free radicals:  These are generally formed by the homolytic cleavage of molecules in reactions taking place in the gas phase or in nonpolar solvents.




Structure of free radicals: The exact structure of free radicals is not known. But one thing is sure that in methyl free radical, carbon atom is sp² hybridised. The three coplanar hybrid orbitals are involved in the formation of three single bonds with other atoms. The unhybridised p orbital which lies in the plane at right angle to the plane of hybrid orbitals carries the odd electron. The bond angle around the carbon carrying the odd electron is nearly 120° each.

Thus alkyl free radicals such as methyl radicals are planar.