What is the difference between tautomerism and metamerism?

Tautomerism and metamerism are different types of structural isomerism.

Structural isomerism is a form of isomerism in which molecules have the same molecular formula but their atoms are connected in different orders.

Structural isomerism is divided into:

• Chain isomerism • Positional isomerism • Functional group isomerism • Tautomerism • Metamerism

Tautomerism

Tautomerism is a dynamic equilibrium between two compounds with same molecular formula.

The most common form of tautomerism is keto-enol tautomerism.

A carbonyl compound containing at least one α-hydrogen atom is converted to an enol by the transfer of an α-hydrogen onto the oxygen atom. For example,

(from chemwiki.ucdavis.edu)

Metamerism

Metamerism is a type of structural isomerism in which different alkyl groups are attached to the same alkyl group.

For example, diethyl ether and methyl propyl ethers are metamers.

##underbrace("CH"_3"CH"_2"-O-CH"_2"CH"_3)_color(red)("diethyl ether")## and ##underbrace("CH"_3"-O-CH"_2"CH"_2"CH"_3)_color(red)("methyl propyl ether") ##

They both contain the ether functional group, but they have different alkyl groups attached to the oxygen atom.