Examine the Fischer projection below. How is this carbohydrate classified?

• A. $D-\mathrm{glucose}$
• B. $D-\mathrm{galactose}$
• C. $L-\mathrm{glucose}$
• D. $L-\mathrm{mannose}$

Answer: (A)

Verified step by step guidance

1. Identify the total number of stereocenters in the Fischer projection. Count the chiral carbons (carbons bonded to four different groups) excluding the aldehyde carbon at the top and the terminal CH2OH group at the bottom.
2. Determine the configuration (D or L) by looking at the chiral carbon farthest from the aldehyde group (usually the second to last carbon). If the hydroxyl group (OH) on this carbon is on the right side, the sugar is classified as a D-sugar; if on the left, it is an L-sugar.
3. Compare the positions of the hydroxyl groups on the other chiral centers to known Fischer projections of common sugars such as glucose, galactose, and mannose. For example, glucose and galactose differ in the orientation of the OH group on the fourth carbon, while mannose differs on the second carbon.
4. Use the pattern of hydroxyl groups (right or left) on each chiral center to match the sugar to one of the known carbohydrates. This involves checking each stereocenter's OH position against standard Fischer projections of D-glucose, D-galactose, L-glucose, and L-mannose.
5. Conclude the classification by combining the D/L designation with the sugar name that matches the stereochemistry of the Fischer projection.