What are #"tautomers"#?
Tautomers are special cases of constitutional isomers that readily interconvert by (typically) the formal migration of an hydrogen atom or a proton
The classic case of tautomerism is given by hydrogen transfer between ketones and enols:
As written, the equilibrium lies strongly to the left. Certain circumstances can drive the equilibrium to the right, as is the case of
Lactams, amides, and amines can undergo related proton transfer to give other examples of tautomerism.
If you wanted to label a ketone with deuterium,