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How can I draw d -glucose in its chair conformation? Why it is the most common aldohexose in nature?

Answer 1

Delilah Anderson

First convert the Fischer projection to a Haworth projection, then convert the Haworth projection to a chair form.

The Fischer projection of glucose is

Convert to a Haworth Projection

Step 1. Draw a basic Haworth projection with the ring oxygen at the top.

#"C-1"# is the atom to the right of the oxygen, and #"C-5"# is the atom to its left.

Step 2. Draw a #"CH"_2"OH"# on #"C-5"#.

Step 3. Draw an #"OH"# below the ring on #"C-1"# for the α form (draw it above the ring for the β form).

Step 4. Draw all the #"OH"# groups on the right side of the Fischer projection on the bottom of the ring. Those on the left go above the ring.

The #"O"# on C-5 is part of the ring.

You can omit the hydrogen atoms, so the Haworth projection for α-D-glucopyranose is

Convert Haworth to Chair

Step 1. Draw a cyclohexane chair in which the #"O"# atom replaces #"C-6"# and the bulky #"CH"_2"OH"# is in the equatorial position.

Step 2. Put all the #"OH"# groups that are "down" in the Haworth projection "down" in the chair. All the other #"OH"# groups go "up".

The chair form of α-D-glucopyranose is

The structure of β-D-glucopyranose is

Prevalence of Glucose

As you move around the β-glucose ring, you see that all the substituents are equatorial.

This is the most stable arrangement possible.

In α-glucose, only the #"OH"# at #"C-1"# is axial.

Every other aldohexose would have more axial substituents and be less stable.

Glucose is the most common hexose because it is the most stable.

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Answer 2

Sarah Angotti

To draw D-glucose in its chair conformation, start with a six-membered ring with five carbons and one oxygen. Position the oxygen above one of the carbons. The hydroxyl groups (-OH) attached to the carbon atoms should alternate above and below the ring. The anomeric carbon (the carbon attached to both the oxygen and the -CH2OH group) should be oriented either up or down, depending on whether it is in the alpha or beta configuration.

D-glucose is the most common aldohexose in nature because it serves as a primary source of energy for living organisms through cellular respiration. Additionally, its structural versatility allows it to serve as a building block for larger carbohydrates such as starch and cellulose, which play crucial roles in plant structure and energy storage. Furthermore, D-glucose is readily available in the form of glucose polymers in foods such as fruits, vegetables, and grains, making it easily accessible for metabolic processes in both plants and animals.

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Answer from HIX Tutor

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