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Anomers

Depending on the orientation of C₁ when the C₅ hydroxyl bonds to it, two different forms can result. These two forms are identical except for the configuration around C₁. These two forms are called anomers , and C₁ is called the anomeric carbon. If the hydroxyl group on C₁ and the -CH₂OH group on C₅ are on opposite sides of the six-membered ring, C₁ is said to be the α anomer. If they are on the same side, C₁ is said to be the β anomer.

Do the α and β anomers have the same properties?

Because they have the same formula, glucose's α and β anomers share many properties, such as their solubility in water, heat of combustion, and ability to reduce certain compounds. Other properties are different, however. For example, α glucose rotates polarized 589 nm light more than β glucose.

Click on the image to switch the configuration of C₁. Then click on the Close Ring button to see which anomer is formed from that configuration. The paper and molecular structures of the product are shown in a similar orientation, with C₁ toward the right. Notice how only the direction of the hydroxyl group on C₁ is different.