α - D(+) Glucose and β - D(+) Glucose are

anomers

The correct answer is Option (1) → anomers.

Let us delve deeper into the relationship between α-D(+) glucose and β-D(+) glucose, emphasizing their classifications and the underlying chemistry involved.

Structure of Glucose

Linear Form: D-glucose is an aldohexose, meaning it contains an aldehyde group (-CHO) and six carbon atoms. The linear structure of D-glucose is represented as follows:

Cyclic Form:

In aqueous solutions, glucose primarily exists in a cyclic form due to a reaction between the aldehyde group and one of the hydroxyl groups. The most common cyclic form is the pyranose structure, which is a six-membered ring.

Anomeric Carbon

When D-glucose cyclizes, the carbonyl carbon (C1) becomes a new stereocenter, leading to the formation of two distinct anomers:

α-D(+) glucose: The hydroxyl group (\(-OH\)) at C1 is below the plane of the ring.

β-D(+) glucose: The hydroxyl group (\(-OH\)) at C1 is above the plane of the ring.

Formation of Anomers:

The cyclization of glucose occurs through a nucleophilic attack of the hydroxyl group on the carbonyl carbon:

If the \(-OH\) on C1 is in the same plane as the \(CH_2OH\) group (C6) after the ring closure, it results in β-D-glucose.

If the \(-OH\) on C1 is opposite to the \(CH_2OH\) group, it results in α-D-glucose.

Representation

α-D(+) Glucose: The cyclic structure is often represented in Haworth projection:

β-D(+) Glucose:

Stereochemistry:

The key difference between α- and β-glucose lies in the orientation of the hydroxyl group on the anomeric carbon (C1).

This difference in configuration is critical, as it influences the molecule's chemical behavior and interaction with other biomolecules.

Mutarotation:

When glucose is dissolved in water, it can undergo mutarotation, where the α and β forms interconvert in solution. This process occurs via the open-chain form:

The ring opens, allowing the aldehyde group to re-form, and then the ring can close again, leading to either the α or β anomer

Biological Significance:

The biological activities of α-D(+) glucose and β-D(+) glucose can differ. For example, β-D-glucose is more prevalent in nature and is a key component of cellulose, whereas α-D-glucose is more commonly found in starch

Summary:

α-D(+) Glucose and β-D(+) Glucose are classified as anomers due to their differing configurations at the anomeric carbon. This distinction plays a vital role in carbohydrate chemistry and biology, influencing their reactivity, stability, and biological functions. Understanding this concept is crucial for studying the chemistry of sugars and their roles in various biological processes.