Question

The aldonic acid of D-glucose forms a five-membered-ring lactone. Draw its structure.

Short answer

Aldonic acid is the product formed by oxidizing aldehyde group of sugar to acid group. The product formed is a five membered lactone.

Step-by-step solution

Structure of D-glucose and aldonic acid of D-glucose

The structure of D-glucose is given below:

Aldonic acid is obtained by oxidation of aldehyde group of an aldose sugar to produce a carboxylic group. This can be done by treating the aldose sugar with bromine water or Tollen’s reagent or Benedict’s reagent.

The structure of aldonic acid of D-glucose is given below:

Step 2: Formation of five-membered lactone

Aldonic acid forms five-membered lactone which is shown below:

Aldonic acid do not exist in hemi acetal forms rather it forms cyclic structure in which ester bond is formed between and group. Such structures are named as lactones.

R is mentioned as the configuration of that particular carbon. It is given according to the priority.

Thus it is proved that aldonic acid of D-glucose gives five membered lactone.