Question

What is the McLafferty rearrangement in mass spectrometry?

Answer 1

I've gone through an example here:
https://socratic.org/questions/what-is-the-mass-spectrum?source=search

The McLafferty rearrangement is the first fragmentation mechanism shown here:

It is a radical-electron rearrangement that occurs when you have a `gamma` hydrogen on a ketone or aldehyde. The `gamma` hydrogen is on the `"C"_gamma`, three away from the carbonyl carbon. All the arrows are one-electron arrows.

In this rearrangement, the `"C"_alpha-"C"_beta` bond is cleaved homolytically (symmetrically), and the oxygen on the carbonyl acquires an `"H"` atom.

The remaining fragmentations are gone into more detail in the linked answer above.