Chapter 24, Problem 35P

Interpretation Introduction

Interpretation:

The aldopentose subjected to the chain extension to form $\text{D-gulonic acid}$ is to be identified from the given structure of $\text{γ-lactone}$ of $\text{D-gulonic acid}$.

Concept introduction:

A furanose is a five-member ring form of a monosaccharide.

The Haworth formula is a representation of carbohydrate in a cyclic form where the substituents point up or down on the ring.

The substituents to the right of the vertical line in Fischer projection will be pointing down and the substituents to the left of the vertical line in a Fischer projection will be pointing up in a Haworth formula.

The aldopentose can be converted to aldohexose through formation of cyanohydrin.

The reaction of hydrogen cyanide with aldose forms cyanohydrin.

The cyanohydrin is a compound in which both a hydroxyl group and a cyano group bonded to the same carbon.

The cyanide group in cyanohydrin on reduction followed by hydrolysis forms aldehyde.

The aldehyde group of monosaccharides (Aldose) oxidized to carboxylic group and forms aldonic acid. Aldonic acids can be named by replacing the $\text{-ose}$ ending of the aldose by $\text{-onic}$ acid.

Aldonic acid forms five-membered $\left(\text{γ}\right)$ lactones. The carboxylic group and the hydroxyl group at $\text{C-4}$ undergo formation of cyclic ester called $\left(\text{γ}\right)$ lactones.