Racemiseksi

Racemiseksi is a Finnish term used in chemistry to describe the process of racemization. In English, racemization refers to the conversion of a chiral molecule into a racemic mixture, which contains equal amounts of its left- and right-handed enantiomers. A racemic mixture typically shows no net optical rotation because the contributions from the two enantiomers cancel each other.

Racemization occurs when the stereocenter of a molecule becomes labile, allowing interconversion between enantiomers. This can proceed through reversible steps that generate achiral intermediates or via configuration inversion at the chiral center. Conditions such as high temperature, extreme pH, light exposure, or catalytic species (acids, bases, or metals) can promote racemization. Some substrates racemize through mechanisms like enolization, iminium formation, or other catalytic pathways that scramble stereochemistry.

Racemization is often described quantitatively by enantiomeric excess (ee). A zero ee indicates a completely racemic mixture, while a nonzero ee indicates predominance of one enantiomer. Optical rotation measurements can also reflect racemization, as the rotation diminishes toward zero with increasing racemate content.

Implications and applications vary by field. In pharmaceuticals and agrochemicals, enantiomers can have markedly different biological activities, so unintended racemization can affect efficacy, safety, and regulatory status. Processes are designed to minimize racemization during synthesis, formulation, and storage, though in some cases racemic mixtures are used intentionally or difficult-to-control racemization is exploited for synthesis.

Analytical methods to study racemization include chiral high-performance liquid chromatography (HPLC), polarimetry, and nuclear magnetic resonance (NMR) with chiral solvating agents or shift reagents. See also: racemization, enantiomer, enantiomeric excess.