Preferred Label : Haworth representation;
IUPAC definition : The Haworth representation of the cyclic forms of monosaccharides can be derived from
the Fischer projection, as follows. The monosaccharide is depicted with the carbon-chain
horizontal and in the plane of the paper, the potential carbonyl group being to the
right. The oxygen bridge is then depicted as being formed behind the plane of the
paper. The heterocyclic ring is therefore located in a plane approximately perpendicular
to the plane of the paper and the groups attached to the carbon atoms of that ring
are above and below the ring. The carbon atoms of the ring are not shown. Groups that
appear to the right of the vertical chain in the Fischer projection (structures A,
D) then appear below the plane of the ring in the Haworth representation (structures
B, C, E). However, at the asymmetric carbon atom (C-5 in A; C-4 in D) involved via
oxygen in ring formation with the carbon atom of the carbonyl group a formal double
inversion must be envisaged to obtain the correct Haworth representation. In the pyranose
forms of d-aldohexoses C-6 will always be above the plane, In the furanose forms of
d-aldohexoses the position of C-6 will depend on the configuration at C-4; it will,
for example, be above the plane in d-glucofuranoses (e.g. C) but below the plane in
d-galactofuranoses (e.g. E).;
Origin ID : H02749;
See also
The Haworth representation of the cyclic forms of monosaccharides can be derived from
the Fischer projection, as follows. The monosaccharide is depicted with the carbon-chain
horizontal and in the plane of the paper, the potential carbonyl group being to the
right. The oxygen bridge is then depicted as being formed behind the plane of the
paper. The heterocyclic ring is therefore located in a plane approximately perpendicular
to the plane of the paper and the groups attached to the carbon atoms of that ring
are above and below the ring. The carbon atoms of the ring are not shown. Groups that
appear to the right of the vertical chain in the Fischer projection (structures A,
D) then appear below the plane of the ring in the Haworth representation (structures
B, C, E). However, at the asymmetric carbon atom (C-5 in A; C-4 in D) involved via
oxygen in ring formation with the carbon atom of the carbonyl group a formal double
inversion must be envisaged to obtain the correct Haworth representation. In the pyranose
forms of d-aldohexoses C-6 will always be above the plane, In the furanose forms of
d-aldohexoses the position of C-6 will depend on the configuration at C-4; it will,
for example, be above the plane in d-glucofuranoses (e.g. C) but below the plane in
d-galactofuranoses (e.g. E).
