tautomerism

is likely misspelled.

has no English definition.

As a noun tautomerism

is a form of isomerism in which a dynamic equilibrium between multiple isomers exists, such as that between an enol and a ketone.

In organic chemistry|lang=en terms the difference between tautomerism and protomeric

is that tautomerism is (organic chemistry) a form of isomerism in which a dynamic equilibrium between multiple isomers exists, such as that between an enol and a ketone while protomeric is (organic chemistry) describing a form of tautomerism in which the isomers differ only in the position of a hydrogen atom (proton).

As a noun tautomerism

is (organic chemistry) a form of isomerism in which a dynamic equilibrium between multiple isomers exists, such as that between an enol and a ketone.

As an adjective protomeric is

(organic chemistry) describing a form of tautomerism in which the isomers differ only in the position of a hydrogen atom (proton).