D and L Configuration of Monosaccharides Quiz

Which of the following is the correct classification of D-glucose?

What is the difference between an anomeric carbon and a chiral carbon in a sugar molecule?

Which of the following is the correct naming convention for the $\alpha$-D-glucopyranose structure shown?

What is the structural difference between an aldose and a ketose sugar?

Which of the following statements about epimers is correct?

What is the structural difference between $\alpha$-D-glucopyranose and $\beta$-D-glucopyranose?

Which of the following is the correct representation of the chair conformation of $\beta$-D-glucopyranose?

What is the relationship between D-glucose and D-fructose?

Which of the following is the correct name for the $\beta$-D-fructofuranose structure shown?

What is the purpose of the Haworth projection in representing monosaccharide structures?

D and L Notations

The letter L is assigned to the structure with the —OH on the left
The letter D is assigned to the structure with —OH on the right
The —OH on the chiral atom farthest from the carbonyl group is used to assign the D or L configuration

Monosaccharides

Also known as simple sugars
Classified by:
- Number of carbons
- Whether aldoses or ketoses
Most (99%) are straight-chain compounds
D-glyceraldehyde is the simplest of the aldoses (aldotriose)
All other sugars have the ending -ose (glucose, galactose, ribose, lactose, etc…)

Aldose Sugars

General formula: H(HC=O)ₙCH₂OH
Aldose sugars have a carbonyl group (HC=O)

Ketose Sugars

General formula: (HC=O)ₙCH₂OH
Ketose sugars have a carbonyl group (HC=O) in a different position

Structure of Sugars

Fisher projection: straight chain representation
Haworth projection: simple ring in perspective
Conformational representation: chair and boat configurations

Haworth Projections

Draw either a six or 5-membered ring including oxygen as one atom
Number the ring clockwise starting next to the oxygen
If the substituent is to the right in the Fisher projection, it will be drawn down in the Haworth projection (Down-Right Rule)
For D-sugars, the highest numbered carbon (furthest from the carbonyl) is drawn up
For L-sugars, it is drawn down
For D-sugars, the OH group at the anomeric position is drawn down for α and up for β
For L-sugars, α is up and β is down

Cyclic Hemiacetals

Can form either furanose or pyranose structures
Five-membered rings are close to being planar
Haworth projections are adequate to represent furanoses
Six-membered rings are more accurately represented as a chair conformation

Test your knowledge on D and L configurations in monosaccharides including the assignments of D and L to specific structures, the use of chiral atoms, and the conventions behind D and L notations. This quiz covers key concepts in stereochemistry of monosaccharides.