Editing Pentose (section)

==Cyclic forms==
The closed or cyclic form of a pentose forms when the [[carbonyl group]] reacts with a [[hydroxyl]] in another carbon, turning the carbonyl into a hydroxyl and creating an [[hemiacetal|ether bridge]] –O– between the two carbons.  This [[intramolecular reaction]] yields a [[cyclic compound|cyclic]] molecule, with a ring consisting of one oxygen atom and usually four carbon atoms; the cyclic compounds are then called [[furanose]]s, for having the same rings as the [[ether|cyclic ether]] [[tetrahydrofuran]].<ref name="m_b">{{cite book|author1=Morrison, Robert Thornton  |author2=Boyd, Robert Neilson|title=Organic Chemistry|publisher=Allyn and Bacon|edition= 2nd}} Library of Congress catalog 66-25695</ref>

The ring closure converts the carbonyl carbon into a [[stereocenter|chiral center]], which may adopt either of two configurations, depending on the position of the new hydroxyl.  Therefore, each linear form can produce two distinct closed forms, identified by prefixes "α" and "β".