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In chemistry, a Haworth projection is a common way of writing a structural formula to represent the cyclic structure of monosaccharides with a simple three-dimensional perspective. Haworth projection approximate the shapes of the actual molecules better for furanoses —which are in reality nearly planar—than for pyranoses that exist in ...
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.
Allulose, also known by its systematic name D-ribo-2-hexulose as well as by the name D-psicose, is a monosaccharide and a ketohexose. [ 2 ] [ 11 ] It is a C3 epimer of fructose . [ 2 ] Fructose can be converted to allulose by the enzymes D -tagatose 3-epimerase ( EC 5.1.3.31 ) and/or D -psicose 3-epimerase ( EC 5.1.3.30 ), which has allowed for ...
In solution, reducing monosaccharides exist in equilibrium between their acyclic and cyclic forms with less than 1% in the acyclic form. The open chain form can close to give the pyranose and furanose with both the α- and β-anomers present for each. The equilibrium population of conformers depends on their relative energies which can be ...
The given definition is the one used by IUPAC, which recommends the Haworth projection to correctly assign stereochemical configurations. [ 4 ] Many authors require in addition that the sugar be bonded to a non-sugar for the molecule to qualify as a glycoside, thus excluding polysaccharides .
Haworth Projection of β-D-glucopyranose. Hermann Emil Fischer won the Nobel Prize in Chemistry (1902) for his work in determining the structure of the D-aldohexoses. [1] However, the linear, free-aldehyde structures that Fischer proposed represent a very minor percentage of the forms that hexose sugars adopt in solution.
Sir Walter Norman Haworth FRS [1] (19 March 1883 [2] – 19 March 1950) was a British chemist best known for his groundbreaking work on ascorbic acid while working at the University of Birmingham. He received the 1937 Nobel Prize in Chemistry "for his investigations on carbohydrates and vitamin C".
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.