What is the Difference Between Aldaric Aldonic and Uronic Acid

The key difference between aldaric aldonic and uronic acid is that aldaric acid has both terminal end functional groups oxidized and aldonic acid has only the aldehyde group oxidized, whereas the end functional groups of uronic acid are not oxidized.

Aldaric acid, aldonic acid, and uronic acid are important chemical compounds having an organic chemical structure with terminal hydroxyl groups and carbonyl groups as functional groups.

CONTENTS

1. Overview and Key Difference
2. What is Aldaric Acid
3. What is Aldonic Acid
4. What is Uronic Acid 
5. Aldaric vs Aldonic vs Uronic Acid in Tabular Form
6. Summary – Aldaric vs Aldonic vs Uronic Acid

What is Aldaric Acid?

Aldaric acid is a type of sugar acid in which the terminal hydroxyl and carbonyl groups of the sugars are replaced by terminal carboxylic acids. This compound can be characterized by HOOC-(CHOH)n-COOH. This compound is usually synthesized by the oxidation of aldoses with nitric acid. This reaction involves the open-chain form of the sugar (polyhydroxyaldehyde) reacting with reactants.

Aldaric acid can be given as an aldose in which both the hydroxyl function of the terminal carbon and the aldehyde function of the first carbon has undergone complete oxidation to form carboxylic acid functions. This means the oxidation of just the aldehyde yields an aldonic acid and the oxidation of just the terminal hydroxyl group yields uronic acid. Typically, aldonic acid cannot form cyclic hemiacetals such as unoxidized uronic acid.

What is Aldonic Acid?

Aldonic acid is an organic compound having the chemical formula HOOC-(CHOH)n-CH2OH. It is any of a family of sugar acids obtained through the oxidation of the aldehyde functional group of an aldose to form a carboxylic acid functional group. This compound has a terminal hydroxyl group that can undergo oxidation instead of the terminal aldehyde, which yields uronic acid. Oxidation of both terminal ends can yield an aldaric acid.

Typically, aldonic acid is prepared by the oxidation of the sugar with bromine. This can be generally found in the lactone form. It has a ring structure that essentially looks similar to the cyclic hemiacetal form of the original sugar. It is the form in the sugar can usually be found. We can find aldonic acid in many biological systems and as products of the oxidation of aldoses via Benedict’s or Fehling’s reagents.

What is Uronic Acid?

Uronic acid can be described as a class of sugar acids having both carbonyl and carboxyl acid functional groups. These sugars having the hydroxyl group furthest from the carbonyl group can be oxidized to carboxylic acid.

If the terminal aldehyde is oxidized, it gives aldonic acid. If both the hydroxyl group and the aldehyde group are oxidized, it gives aldaric acid. The name of a particular uronic acid is generally created based on the parent sugar molecule. For E.g. the uronic acid analog of glucose is glucuronic acid. Moreover, uronic acids created from hexoses are named hexuronic acids. Uronic acids derived from the pentoses are named penturonic acids.

What is the Difference Between Aldaric Aldonic and Uronic Acid?

Aldaric, aldonic, and uronic are important organic compounds that can be categorized as sugar acids. The key difference between aldaric aldonic and uronic acid is that aldaric acid has both terminal end functional groups oxidized, and aldonic acid has only the aldehyde group oxidized, whereas the end functional groups of uronic acid are not oxidized.

The following table summarizes the difference between aldaric aldonic and uronic acid.

Summary – Aldaric vs Aldonic vs Uronic Acid

Aldaric acid is a type of sugar acid in which the terminal hydroxyl and carbonyl groups of the sugars are replaced by terminal carboxylic acids. Aldonic acid is an organic compound having the chemical formula HOOC-(CHOH)n-CH2OH. Uronic acid is a class of sugar acids having both carbonyl and carboxyl acid functional groups. The key difference b aldaric aldonic and uronic acid is that aldaric acid has both terminal end functional groups oxidized and aldonic acid has only the aldehyde group oxidized, whereas the end functional groups of uronic acid are not oxidized.

Reference:

1. “Aldaric Acid.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “D-Gluconic acid” By Edgar181 at English Wikipedia – Transferred from en.Wikipedia to Commons. (Public Domain) via Commons Wikimedia
2. “Beta-D-Glucose” By Yikrazuul – Own work (Public Domain) via Commons Wikimedia