91Ó°ÊÓ

When an organic compound in the gaseous phase is bombarded with electrons, the ionization electron of the compound is removed.

This causes the formation of a molecular ion with high energy. The molecular ion stabilizes by fragmentation into shorter fragments.

A common mode of fragmentation in molecular ions with a functional group is alpha-cleavage in which $\mathrm{C}-\mathrm{C}$bond is broken at the alpha position of the functional group.

An alpha-cleavage of molecular ion produces a cation and a free radical.

The cation travels through a mass spectrometer and produces a line in the mass spectrum while free radical is removed by the vacuum pump.

(a) Alpha-cleavage can be done on either side of the carbonyl group forming 2 products.

Alpha-cleavage of (a)

(b) Alpha cleavage occurs at the alpha position of the hydroxyl group

alpha-cleavage of (b)

(c) Alpha-cleavage can occur at either side of the carbonyl group

Alpha-cleavage of (c)