What it does
Glucose is drawn three ways in Class 12 chemistry: as an open chain (the Fischer projection), as a six-membered ring (the Haworth projection), and as one of two rings, α or β, that differ only at the first carbon. This page puts the chain and the ring side by side so you can see how one becomes the other.
- Pick D-glucose, D-galactose, D-mannose or L-glucose. The Fischer projection is on the left and the ring on the right.
- Tap a carbon (or the C1 to C5 buttons). The same carbon lights up in both drawings, and a line explains where its –OH went.
- Flip between the α ring and the β ring and watch only C1 change.
- Mutarotation: start with pure α or pure β glucose in water, play or drag the time, and see the rotation of polarised light drift to +52.7° as the ring opens and closes.
It fits Class 12 Chemistry: biomolecules (glucose structure, cyclic forms, anomers, D and L configuration, mutarotation). For the stereocentres themselves see r/S checker, and for the reactions that link the aldehyde group to other families use the organic reaction map.
How to use it
- Choose a sugar and α or β.
- Tap a carbon. The table lists every carbon with the side of its –OH in the Fischer projection and the direction in the ring; the row you picked is bold.
- Read the rule: right in Fischer → down in Haworth; left → up. C5’s –OH closes the ring, so it becomes the ring O and its CH₂OH points up for a D sugar and down for an L sugar.
- At C1, α puts the –OH on the opposite face to CH₂OH and β on the same face.
- In Mutarotation, press Start pure α or Start pure β, then Play or drag the time slider up to 6 hours. The line under the graph fills in the mixture rule with the live shares of α and β.
- Check yourself gives five fresh questions: Fischer to Haworth, α or β, a rotation to work out, a share of α from a measured rotation, and D or L.
Worked example
Pick D-glucose. In the Fischer projection the –OH groups on C2, C3, C4 and C5 are on the right, left, right and right. In the ring, C2 points down, C3 up, C4 down, and the CH₂OH on C5 up (it is a D sugar). In the β ring the C1 –OH points up, so the groups alternate all the way round: this is why β-glucose is the more stable form.
Now the mutarotation numbers. α is +112°, β is +18.7°, and the equilibrium mixture is +52.7°. The share of α at equilibrium is (52.7 − 18.7) ÷ (112 − 18.7) = 34 ÷ 93.3 = 0.364, so about 36 % α and 64 % β. Drag the time to 60 minutes after starting with pure α: the page shows about 67 % α and a rotation of about +82°.
Tips
- Galactose differs from glucose only at C4 and mannose only at C2: such sugars are epimers.
- D and L describe the side of the C5 –OH in the Fischer projection, not the direction the sugar turns light. D-glucose happens to be dextrorotatory (+), but D-fructose is laevorotatory (−).
- The open chain is always there, but under 1 %; that is enough for glucose to reduce Tollens’ and Fehling’s reagents.
FAQ
Why can’t glucose’s ring be seen in its reactions with NaHSO₃? Because so little open chain is present. That puzzle is one of the clues that led chemists to the ring structure.
Is the mutarotation speed real? The rotations are real rounded values; the speed is illustrative. Temperature, acid and base all change it.
What about fructose? Fructose is a ketose that forms a five-membered (furanose) ring, which this page does not draw.
Where the numbers come from
- Fischer and Haworth projections, the right-is-down rule, α and β anomers and D and L sugars are standard carbohydrate chemistry. The drawings and wording are fibub's own.
- Specific rotations of α-D-glucose (+112°), β-D-glucose (+18.7°) and the equilibrium mixture (+52.7°) are rounded, widely quoted values. The rate of mutarotation is an illustrative room-temperature value, not a measurement; it is labelled as such on the page.
- Checked in the tests against the standard Haworth descriptions of the D-glucose, D-galactose and D-mannose pyranoses and the 36 : 64 α : β equilibrium. Nothing you choose is stored or sent anywhere.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.