Tautomerism can be divided into,
Open system Ring system
Open system The example considered earlier(in the previous page)is one such type (keto - enol), this type is also called Prototropy since it involves the actual migration of a proton.
Open system can also be further classified as follows,
DIAD system: It involves the migration from atom 1 to 2 .
TRIAD system: This involves migration from atom 1 to atom 3.
Keto-enol tautomerism
Lactam-lactim
Nitro – oximino (nitroso – isonitroso)
Oxime-Nitroso
Ring systems
A good example of this type is the glucose molecule which exists in solution as a equilibrium mixture of the open chain form which is an aldose and the ring form ( α and β glucose)