91Ó°ÊÓ

Fragmentation occurs when high-energy cation radical flies apart by spontaneous cleavage of the bond. One fragmentis carbocation while the other fragment is a neutral radical.

The positive charge often remains with a more stable carbocation that forms.Carbocations are electron-deficient species.

Alpha-cleavage ($\mathrm{Î\pm }$-cleavage) isthe breaking ofa carbon-carbon bond adjacent to the carbon bearing a specified functional group. Here, cleavage forms one carbocation and one radical.

Cleavage can occur on either side of the molecule but practically occurs on the side which gives more stable carbocation. So, this gives two products if asymmetric molecule.

In mass spectrometry, this process involvesthe β-cleavage of carbonyl-containing radical cation to produce an enol radical cation and an alkene.

For Mc-Lafferty rearrangement $\mathrm{γ}$hydrogen is needed.

• Mc-Lafferty rearrangement
• Alpha-cleavage ($\mathrm{Î\pm }$-cleavage)

Here it can be seen two fragments are formed on β-cleavage one is alkene and other is enol radical cation.

As given molecule is asymmetric and has carbon on both side of carbonyl group so here cleavage on both side can occur resulting in forming two carbocation and two radical molecules.

As here no $\mathrm{γ}$hydrogen is present so this reaction of the Mc-Lafferty rearrangement is not possible.

As given molecule is asymmetric and has carbon on both side of carbonyl group so here cleavage on both side can occur. One cleavage will cleave methyl radical and the other will result in cleavage of the cyclic ring giving carbocation radical molecule.