Predict the products obtained when d-galactose reacts with each reagent. (a) Br2 and H2O

Verified step by step guidance

1. Identify the functional groups present in D-galactose. D-galactose is an aldohexose, meaning it contains an aldehyde group at the C-1 position and multiple hydroxyl groups.
2. Understand the role of the reagent Br2 in water. Bromine in water is a mild oxidizing agent that specifically oxidizes aldehyde groups to carboxylic acids.
3. Predict the reaction outcome. The aldehyde group at the C-1 position of D-galactose will be oxidized to a carboxylic acid, converting D-galactose into D-galactonic acid.
4. Consider the stereochemistry. The stereochemistry at the other chiral centers (C-2 to C-5) in D-galactose remains unchanged during this reaction.
5. Summarize the product. The product of the reaction is D-galactonic acid, where the aldehyde group of D-galactose is converted to a carboxylic acid, while the rest of the molecule remains the same.

Key Concepts

D-Galactose Structure

D-galactose is a six-carbon aldose sugar with a specific stereochemistry. It contains an aldehyde functional group and multiple hydroxyl groups, which are crucial for its reactivity. Understanding its structure helps predict how it will interact with reagents, particularly in oxidation and substitution reactions.

Bromination Reaction

The reaction of sugars with bromine in the presence of water typically leads to the formation of bromohydrins. In this case, Br2 and H2O can oxidize the aldehyde group of d-galactose, resulting in the formation of a brominated sugar. This reaction is an example of electrophilic addition, where the bromine acts as an electrophile.

Oxidation of Sugars

Oxidation of sugars involves the conversion of alcohols or aldehydes into carbonyl compounds or carboxylic acids. In the case of d-galactose reacting with Br2 and H2O, the aldehyde group can be oxidized to a carboxylic acid, leading to the formation of products like galactonic acid. This transformation is significant in carbohydrate chemistry and metabolic pathways.