Mutarotation

Part of speech: noun

Definitions

1. The phenomenon of a cyclic sugar solution changing optical rotation due to the interconversion between different anomers via the open-chain form
2. The process by which certain sugars in aqueous solution undergo spontaneous change in specific optical rotatory power as their structural forms equilibrate
3. The transformation in which saccharides alter their stereochemistry at the anomeric carbon, causing a shift in observed optical activity over time in solution

Etymology: Mutarotation is a compound built from two parts: "muta-", a combining form of the Latin "mutare" meaning "to change," and "rotation," from the Latin "rotatio," which comes from "rota," a wheel. Put together, the name describes a change in rotation, and in chemistry it refers to the shift in optical rotation that a sugar solution shows over time as its molecules settle into a new balance. The "rotation" half carries the physical picture. When a solution of certain sugars is placed in a polarimeter, which measures how far it turns the plane of polarized light, the reading starts at one value and then drifts until it stops at a steady figure. That drift is the mutarotation. The rotation itself reflects how sugar molecules are arranged in space, so a changing reading means the molecules are changing their arrangement in solution. Because the term is a transparent coinage from familiar Latin roots, it needed no special origin story: it names the change in rotation directly, and its parts are easy to see.

Synonyms: optical rotation change, anomeric change