Monosaccharides are polyhydric aldehydes and ketones which cannot be hydrolysed into simpler carbohydrates. The monosaccharides containing `-CHO` group are called aldoses while those containing `C=O` group are called ketoses. The aldehyde group is always present at `C_(1)` while keto group is generally present at `C_(2)`. All monosaccharides are oxidised by Tollen's reagent and Fehling solution and are called reducing sugars.
The monosaccharide molecules may be assigned D and L-configurations depending upon whether the configuration of the molecule is related to D- or L-glyceraldehyde. If the `-OH` group is attached to the carbon adjacent to the `-CH_(2)OH` group (last chiral carbon) is on the right hand side, it is assigned D-configuration. The molecule is assigned L-configuration if the -OH group attached to the carbon adjacent to the `-CH_(2)OH` group is on the left. The monosaccharides contain one or more chiral carbon atoms. Pentoses and hexoses have cyclic structures furanose (five membered) and pyranose (six membered). During cyclization, `C_(1)` in aldohexoses and `C_(2)` in fructose become chiral and the newly formed -OH group may be either on the left or on the right in Fischer projection formulae. These monosaccharides, therefore, exist in two stereoisomeric forms called `alpha`-anomer and `beta`-anomer while `C_(1) and C_(2)` are called glycosidic or anomeric carbon. The bonds joining glycosidic carbon are called glycosidic linkages. `D(+)` glucose exists in two stereoisomeric forms, `alpha`-D- glucose and `beta`-D-glucose. When either of these two forms of glucose i.e., `alpha-D-`glucose are dissolved in water and allowed to stand, these get slowly converted into other form and an equilibrium mixture of both is formed. This process is called mutarotation.
Two forms of D-glucopyranose are called

Options

A. epimers
B. anomers
C. enantiomers
D. diastomers.

Answer

To answer the question regarding the two forms of D-Glucopyranose, we will follow these steps:

### Step 1: Understand the Structure of D-Glucopyranose
D-Glucopyranose is a six-membered cyclic form of glucose. It contains an anomeric carbon, which is the carbon that becomes chiral during the cyclization process.

**Hint**: Remember that the anomeric carbon is crucial for distinguishing between the two forms of glucose.

### Step 2: Identify the Two Forms
The two forms of D-Glucopyranose are known as alpha (α) and beta (β) anomers. The difference between these two forms lies in the position of the hydroxyl (-OH) group attached to the anomeric carbon (C1).

**Hint**: Focus on the position of the -OH group on the anomeric carbon to differentiate between alpha and beta forms.

### Step 3: Define Alpha and Beta Forms
- In the **alpha (α)** form, the -OH group on the anomeric carbon is positioned **below** the plane of the ring.
- In the **beta (β)** form, the -OH group on the anomeric carbon is positioned **above** the plane of the ring.

**Hint**: Visualize the cyclic structure to see how the -OH group can be above or below the plane.

### Step 4: Conclusion on Terminology
The two forms of D-Glucopyranose are collectively referred to as **anomers**. This term specifically describes the relationship between the two stereoisomers that differ at the anomeric carbon.

**Hint**: Remember that "anomers" is a specific term used for sugars that differ at the anomeric carbon.

### Final Answer
The two forms of D-Glucopyranose are called **anomers**.