What Happens When Glucose Cyclizes?

James H. Sterling
James H. Sterling
• • 7 min read

When an Aldose Aldose an Aldose Is a Monosaccharide (A Simple Sugar) with a Carbon Backbone Chain with a Carbonyl Group on the Endmost Carbon Atom, Making It...

What Happens When Glucose Cyclizes?

When an aldose

aldose
An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms.
› wiki › Aldose
cyclizes, the hydroxyl group on the second to last carbon undergoes an intramolecular reaction with the carbonyl group of the aldehyde. The product resulting from aldose cyclization is a hemiacetal
hemiacetal
A hemiacetal or a hemiketal have the general formula R1R2C(OH)OR, where R1 or R2 is hydrogen or an organic substituent. They generally result from the addition of an alcohol to an aldehyde or a ketone, although the latter are sometimes called hemiketals. Most sugars are hemiacetals.
› wiki › Hemiacetal
. The cyclization of glucose is shown below with the group characteristic of a hemiacetal shown in red.

What can fructose Cyclize to?

Fructose has a ketone group and five hydroxyl groups. So, fructose should also be able to cyclize to form an intramolecular hemiketal.

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How does glucose become cyclic?

The terms "glucose" and "D-glucose" are generally used for these cyclic forms as well. The ring arises from the open-chain form by an intramolecular nucleophilic addition reaction between the aldehyde group (at C-1) and either the C-4 or C-5 hydroxyl group, forming a hemiacetal linkage, −C(OH)H−O−.

James H. Sterling

James H. Sterling

Environmental Science & Climate Journalist
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James Sterling reports on renewable energy developments, climate policy, ecological conservation, and green tech innovations around the globe.