The document discusses the Haworth representation of cyclic hemiacetals, particularly D-glucose, highlighting its advantages over the Fischer projection in accurately depicting molecular shape. It explains the planar hexagonal structure introduced by W.N. Haworth and the relationships between various group orientations in the projections. Additionally, it notes that the actual conformation is chair-like, confirmed by x-ray studies, and describes the equatorial and axial positions of substituents in the anomers of D-glucose.

1. The Haworth Representation
Written By: Amir Hassan Govt. Post Graduate College Mardan KP Pakistan.
The Haworth Projection or, Representation:
 The Fischer projection does not accurately describe the shape of the cyclic hemiacetal form of D
– Glucose (as shown in figure A).
 A formulation suggested by the English chemist W.N. Haworth in which ring are written as flat
or, planar hexagons is more correct.
 Haworth taught that these structures are awkward and spatial relations are confused.
 When a cyclic form of glucose is represented in this way the lower thickened edge of the ring is
assumed to be nearest the reader.
 The groups projected to the right in the Fishcer projection go below the plane of the ring, those to
the left go above.
The following series of formula should explain the relation between two the two conventions without
further comments.
Figure A

2. The Haworth Representation
Written By: Amir Hassan Govt. Post Graduate College Mardan KP Pakistan.
A simple way of drawing Haworth projection is to omit the ring carbon. Thus α – D – glucose
and β – D – glucose may be represented as shown;
actually the cyclic form of glucose preferentially exists in the non planar chair conformation like
those of cyclohexanes. This has been confirmed by X – ray studies.
Since it is inconvenient to draw such non planer projection we will use the planar Haworth
projections.

3. The Haworth Representation
Written By: Amir Hassan Govt. Post Graduate College Mardan KP Pakistan.
Haworth introduced the hexagonal representation resembling the heterocyclic pyran which
consists of five carbons and one oxygen in the ring. Thus claimed the names α-D-glucopyranose
and β-D-glucopyranose for α-D-glucose and β-D-glucose. In Haworth formula all the OH groups
on the right in the Fischer Formula are directed below the plane of the ring while those on the
left go above the plane.
Conformation. Studies of the structure of the cyclic hemiacetal form of D-(+)-GLUCOSE using X-
ray analysis have shown that actual conformation of the ring are the chair form with the oxygen atom at
the upper right represented by conformational formula, 3 and 6. It is interesting to that in the β-anomer of
D-glucose all the large substituent –OH or –CH2OH are equatorial. In the α-anomer the only bulky axial
substituent is the –OH at C -1.

4. Written By
Amir Hassan
Govt Post Graduate College Mardan KP Pakistan.
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