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In NCERT you draw glucose as a hexagon with an oxygen in one corner and call it a Haworth structure. The name belongs to a chemist who started work at 14 in a linoleum factory. This post covers what Walter Haworth found about sugars, why it explains the difference between starch and cotton, how his chain-counting method worked, and his part in the vitamin C story.
Who was Walter Haworth?
His Nobel biography records that he was born at Chorley, Lancashire, on 19 March 1883 and left school at 14 to learn linoleum design with his father. The dyestuffs used in that work got him interested in chemistry. After private tuition he entered Manchester in 1903 under W. H. Perkin Jr, then took a doctorate at Göttingen. He worked at St Andrews from 1912, Durham from 1920 and Birmingham from 1925 until he retired in 1948. He was knighted in 1947 and died on 19 March 1950.
He shared the 1937 Nobel Prize in Chemistry with Paul Karrer, his half "for his investigations on carbohydrates and vitamin C".
Why did sugars need a new structure?
In his Nobel lecture, Haworth explained that Emil Fischer had drawn sugars as open-chain aldehydes and ketones, and those configurations "will always be regarded as classical". But it was not until 1925 that a precise structural model of any sugar was finally settled. That year he published a revision of the structural formula of glucose in Nature: a ring of six atoms, five carbons and one oxygen, with one carbon in a side chain. He called this the pyranose form, after pyran. Less stable five-membered rings he called furanose forms, after furan. Their glycosides were hydrolysed roughly 100 times faster than the normal ones.
His tool was methylation. The Nobel biography explains that at St Andrews he extended Fischer's reaction of sugars with methanol into a method of preparing fully methylated derivatives, which let him work out which hydroxyl groups were tied up in rings and links. The NCERT Class 12 Biomolecules unit uses his names today: pyranose for glucose, furanose for fructose, both drawn as Haworth structures. Our post on glucose's cyclic forms shows how to draw them.
Why are starch and cellulose so different?
Both are chains of glucose. Haworth's lecture gives the reason they behave so differently. In maltose, the repeating unit of starch, an α-glucose unit is joined from C1 to C4 of the next. In cellobiose, the unit of cellulose, the link is also C1 to C4, but from the β form. That single difference in the direction of one bond at C1 makes cellulose chains nearly straight, with each alternate unit flipped, which is why cellulose forms fibres. Starch chains curve away from a straight line.
He also explained sucrose: C1 of glucose (a pyranose ring) is joined to C2 of fructose (a furanose ring). Both reducing positions are used up in the link, so sucrose is a non-reducing sugar.
Worked example: counting chain length by end groups
Haworth's end-group assay works like this. Methylate every free OH group of a polysaccharide, then hydrolyse it. A unit in the middle of a chain has three free OH groups and gives trimethyl glucose. The non-reducing end unit has four free OH groups and gives tetramethyl glucose. So one tetramethyl unit marks the end of one chain.
His lecture says starch chains end after 26 to 30 glucose units. For a 26-unit chain, the tetramethyl fraction is 1 ÷ 26 = 3.8% of the units.
Molar mass of that chain: each glucose residue in a chain is C6H10O5, 162.14 g mol⁻¹. Add one water for the two chain ends: 26 × 162.14 + 18.02 = 4234 g mol⁻¹.
For cotton cellulose, he found one tetramethyl glucose for every 190 trimethyl units, so the tetramethyl fraction was only 1 ÷ 191 = 0.52%, and the chains were at least that long.
Common mistakes to avoid:
Using 180 for each unit. Free glucose is 180.16, but each link loses one water, so a residue in a chain is 162.14.
Mixing up α and β. Haworth's lecture puts the C1 hydroxyl below the plane of the ring in the α form and above it in the β form.
Calling sucrose reducing. Its link uses both anomeric carbons, so it has no free one.
If ring structures still feel abstract, the Fermi Concept Library covers every concept in physics, chemistry, biology, mathematics and computing, one idea at a time.
What was his part in the vitamin C story?
Haworth's lecture recalls that Albert Szent-Györgyi visited Birmingham and asked him to study a strongly reducing acid, C6H8O6, called hexuronic acid. Once it was linked to vitamin C, the two men renamed it ascorbic acid. X-ray work in his lab by Dr Cox showed the molecule was unusually flat, which helped choose between possible formulas. Its structure, a lactone of 2-keto-L-gulonic acid, was announced from Birmingham early in 1933. Haworth and E. L. Hirst, and at the same time the chemist Reichstein, then made it synthetically. Our post on Szent-Györgyi and the isolation of vitamin C tells the other half.
What can a student learn from Haworth?
A late start is not a closed door. He began as a factory apprentice.
Study related things together. His lecture says that in a hard problem "all the available polysaccharides should be studied together as a group".
Use a method that counts. The end-group assay turned a structural question into arithmetic.
Try it now: if a methylated glycogen sample gives one tetramethyl glucose for every 11 trimethyl glucose units, how many units are in each chain?
