isomerically

Isomerically is an adverb used in chemistry to describe something that pertains to isomerism, the phenomenon whereby compounds share the same molecular formula but differ in the arrangement of atoms or spatial orientation. The word derives from isomeric, itself from Greek isos “equal” and meros “part,” with the suffix -ally forming an adverb.

The term is used to modify nouns or phrases that refer to isomeric forms or processes. Common usages include “isomerically pure” (containing a single isomer), “isomerically enriched” or “isomerically separated” (isolating a particular isomer), and “isomerically labeled” (tagging a molecule to indicate a specific isomer). For example, “The sample was isomerically enriched for the R enantiomer.”

Isomerically appears in discussions of stereoisomerism (optical isomerism and diastereomerism) as well as structural isomerism. In chiral chemistry, more precise terms such as enantiomerically pure or diastereomerically enriched may be preferred to avoid ambiguity; isomerically is broader but less specific.

Etymology and usage: the form is primarily used in scientific writing and denotes relation to isomeric forms or processes. It should not be confused with isomerization, which denotes conversion between isomers. Related terms include isomer, isomerism, enantiomer, and diastereomer.