metisomerism

Metisomerism is a type of stereoisomerism that occurs in molecules where the same molecular formula exists but the connectivity of atoms differs due to the migration of a functional group or a part of a molecule. This migration results in a change in the position of a double bond or a heteroatom. Unlike structural isomers that have entirely different arrangements of atoms, metamerism involves a subtle rearrangement, typically of an alkyl group attached to a functional group. For instance, in ethers, metamerism can be observed when an alkyl group is shifted from one side of the oxygen atom to the other, leading to different structural formulas while maintaining the same ether linkage. This phenomenon is distinct from tautomerism, which involves the rapid interconversion of isomers. Metamerism requires a complete bond breaking and reformation process to interconvert the isomers. The key characteristic of metamerism is the variation in the alkyl chains attached to a polyvalent atom or functional group, such as in ethers, thioethers, secondary and tertiary amines, and ketones. For example, diethyl ether and methyl propyl ether are metamers, as both have the molecular formula C4H10O and contain an oxygen atom, but the distribution of carbon atoms around the oxygen is different.