Homometamerie

Homometamerie, or homometamerism, is a concept in organic chemistry describing a specific type of isomerism. It refers to compounds that share the same molecular formula and the same set of metameric units, but differ in the distribution or arrangement of those identical units along the molecular backbone. In other words, the metameric blocks are identical, and the variation arises from where those identical units are located within the structure. This distinguishes homometamerie from heterometamerie, where the metameric units themselves are not identical.

The concept is most frequently discussed in the context of polymers and oligomers, where repeating or exchanging identical blocks can lead to distinct constitutional isomers despite an unchanged overall composition. For example, a series of diester or diol compounds built from the same repeating units may exhibit different connectivity because the identical functional groups occupy different positions along the chain. Although more common in macromolecular chemistry, homometameric relationships can also be relevant for smaller, symmetry-rich molecules where identical sites are arranged in different sequences.

Characterization of homometamerie relies on standard analytical methods such as nuclear magnetic resonance spectroscopy, mass spectrometry, and chromatographic techniques. Distinguishing homometameric isomers from other constitutional or regioisomers often requires careful analysis of the sequence and connectivity of the identical metameric units.

The term suggests a systematic way to categorize isomers that differ solely by the position of identical units within a structure, expanding the framework of metamerism in chemical nomenclature and analysis.