The letter `D` in D-glucose signifies.

Options

A. dextrorotatory
B. configuration
C. diamagnetic nature
D. mode of synthesis

Answer

To understand what the letter 'D' in D-glucose signifies, we can break down the explanation into the following steps:

### Step 1: Definition of D-Glucose
D-glucose is a simple sugar (monosaccharide) that is an important carbohydrate in biology. It is one of the primary sources of energy for cells.

### Step 2: Chiral Centers in Glucose
Glucose has multiple chiral centers. A chiral center is a carbon atom that has four different groups attached to it. In the case of D-glucose, it has six carbon atoms, and among them, several are chiral.

### Step 3: Configuration Reference
The letter 'D' in D-glucose refers to the configuration of the molecule based on the orientation of the hydroxyl (-OH) group on the penultimate (second to last) carbon atom.

### Step 4: D and L Notation
The 'D' and 'L' notation is derived from the structure of D-glyceraldehyde, which is the simplest aldose sugar. In D-glyceraldehyde, the hydroxyl group on the chiral carbon farthest from the aldehyde group (the second carbon) is on the right side in a Fischer projection. If the hydroxyl group is on the right, it is classified as 'D'; if it is on the left, it is classified as 'L'.

### Step 5: Conclusion
Therefore, the 'D' in D-glucose signifies that the hydroxyl group on the second carbon (the penultimate carbon) is on the right side in its Fischer projection, indicating its configuration relative to D-glyceraldehyde.

### Final Answer
The letter 'D' in D-glucose signifies that it has the same configuration as D-glyceraldehyde, specifically that the hydroxyl group on the second carbon is on the right side in the Fischer projection.

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