Uric Acid Structure: Detailed Explanations

Uric acid is a well known chemical compound of mammal body, which appears as white crystals physically.

For the heterocyclic formation with two configuration, keto and enol, we see many properties which are mentioned in this article.

Skeletal of Uric acid:

Two cyclic rings are connected to produce the Uric acid structure; among these one is six member ring and another is five member ring with the chemical formula C5H4N4O3.

As the ring contains atoms other than Carbon and Hydrogen which are Nitrogen and Oxygen, so the compound Uric acid is called hetero- cyclic compound.

The IUPAC (International Union of Pure and Applied Chemistry) name of Uric acid is 7,9-Dihydro-1H-purine-2,6,8(3H)-trione and the other chemical names of this structure are 1H-Purine-2,6,8-trione, 2,6,8-Trioxypurine, 2,6,8-Trioxopurine etc.

uric acid structure
uric acid structure

Formation of Uric acid:

Uric acid is produced through a complex pathway from purine nucleotides of animal proteins mainly in liver, intestines where different types of enzymes are involved in the process like deaminase, xanthine oxiddase, catalysis the reaction.

Uric acid is synthesised mainly from two substances, Adenosine monophosphate and Guanine monophosphate which are converted to Adenosine and Guanosine respectively by nucleotidase.

In the further reaction inosine and guanosine produce hypoxanthine and guanine respectively; from where Hypoxanthine is oxidized (removal of electron) by the enzyme called xanthine-oxidase to Xanthine and Guanine is deaminated to Xanthine.

Finally Xanthine is oxidized means removal of electrons or addition of Oxygen, by the enzyme, Xanthine oxidase to form the product Uric acid.

Ions and salt of Uric acid:

Uric acid is a weak acid which can release Hydrogen ion (H+) and produced its ion Urate with having negative charge on it, hence both form weak acid-conjugate base pair. The negative charge can delocalize through ring, give stability to structure.

In blood Sodium ion (Na+) is one of the main cation present which can interact with the Urate ion as it is negatively charged compound  and both the oppositely charged particles form the salt called monosodium urate.

uric acid structure
ion of uric acid structure (urate ion)

Tautomerism of Uric acid structure:

If structural isomers (structures with same chemical formula but different bonding patterns) rapidly inter converted then they called tautomers and the chemical process is called tautomerization.

In Uric acid structure, there are three carbonyl carbon atoms (keto form) which can convert to enol form by taking Hydrogen ion from the hetero atom Nitrogen. Hence the chemical formula remains same, we see two different configurations.

uric acid structure
lactam configuration of uric acid structure

The keto configuration is called Lactam and the enol configuration is called Lactim configuration of the Uric acid.

uric acid structure
lactim configuration of uric acid structure

Aromaticity of the ring in acid structure:

If the heterocyclic compounds have conjugated planar ring system means the pi (π)-electrons can spread over the ring with (4n + 2) pi (π) electrons the hetero cyclic compounds become aromatic in nature.

In Uric acid there are two cyclic rings present and also we see two tautomeric form of Uric acid, one is Lactam and another is Lactim. In lactim structure we see the extended electronic conjugation means they can delocalize.

Solubility of Uric acid:

Solubility of Uric acid and its salts depend on the concentration that soluble in the solution at standard condition, for water which is very low. They can be soluble in hot water rather than cold water.

This low solubility can cause easy crystallization for the salts of the Uric acid. In Ethanol the solubility of Uric acid and its salts are nearly negligible.

Acidic nature of Uric acid:

Acidic nature of the Uric acid depend on the ability to release the Hydrogen ion (H+) in medium as the measurement parameter of acidity is pH which is the negative logarithm of the Hydrogen ion (H+) concentration.

If any compound release large concentration of (H+) ion the pH value will be small, called strong acid where as if the opposite happen, the compound becomes weak acid. The Lactim form of Uric acid have three (-OH) group, one in five member ring, others in six member ring.

When Urate ion forms the (-OH) groups of the six member ring don’t release any (H+) ion, only the (-OH) group of the five member ring release (H+) ion due to stabilization factor.

Hence for low hydrogen ion concentration Uric acid becomes a weak acid with pKa around 5.6. However depending on the medium uric acid can release more than one proton (H+) and become polyprotic acid.

Effect of excessive Uric acid in blood:

Uric acid is a sparingly soluble molecule, hence if its concentration in blood increases, due to the low solubility it start to form sharp crystals as precipitation around the joints, causes pain.

Hence taking of Purine rich foods in large amounts daily must be avoided. Low level of Uric acid in blood also causes different problems.


For the tautomeric forms of uric acid it shows different properties.