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Relationship between the acyclic and the cyclic isomers of fructose d - and l-isomers of fructose (open-chain form) Fructose is a 6-carbon polyhydroxyketone. [16] Crystalline fructose adopts a cyclic six-membered structure, called β-d-fructopyranose, owing to the stability of its hemiketal and internal hydrogen-bonding.
In chemistry, an open-chain compound (or open chain compound) or acyclic compound (Greek prefix α 'without' and κύκλος 'cycle') is a compound with a linear structure, rather than a cyclic one. [1] An open-chain compound having no side groups is called a straight-chain compound (also spelled as straight chain compound).
Sugars with ketone groups in their open chain form are capable of isomerizing via a series of tautomeric shifts to produce an aldehyde group in solution. Therefore, ketones like fructose are considered reducing sugars but it is the isomer containing an aldehyde group which is reducing since ketones cannot be oxidized without decomposition of ...
The carbons of the chain are conventionally numbered from 1 to n, starting from the end which is closest to the carbonyl. If the carbonyl is at the very beginning of the chain (carbon 1), the monosaccharide is said to be an aldose, otherwise it is a ketose. These names can be combined with the chain length prefix, as in aldohexose or ...
For many monosaccharides (including glucose), the cyclic forms predominate, in the solid state and in solutions, and therefore the same name commonly is used for the open- and closed-chain isomers. Thus, for example, the term "glucose" may signify glucofuranose, glucopyranose, the open-chain form, or a mixture of the three.
The conventional numbering of the carbons in the closed form is the same as in the open-chain form. If the sugar is an aldohexose, with the carbonyl in position 1, the reaction may involve the hydroxyl on carbon 4 or carbon 5, creating a hemiacetal with five- or six-membered ring, respectively.
The open-chain form of a monosaccharide often coexists with a closed ring form where the aldehyde/ketone carbonyl group carbon (C=O) and hydroxyl group (–OH) react forming a hemiacetal with a new C–O–C bridge. Monosaccharides can be linked together into what are called polysaccharides (or oligosaccharides) in a large variety of ways. Many ...
English: D-Fructose: interconversion of open-chain form, furanose and pyranose. Created with ChemDoodle 7.0.2 and Adobe Illustrator CC 2017 . Eesti: Suhe lahtise ahelaga vormi ja tsükliliste vormide (pooltatsetaalide) isomeeride vahel.