Gluconic acid is an organic compound that is also termed Dextronic acid and is one of the 16 stereoisomers of 2,3,4,5,6-pentahydroxyhexanoic acid. Its IUPAC name is D-Gluconic acid, and it has a molecular formula of C₆H₁₂O₇. It is a non-toxic compound that can be found in honey, wine, fruits, etc. It appears as a colourless to light yellow, clear, syrupy liquid and has a mild acid taste. It is very soluble in water, slightly soluble in alcohol, and insoluble in ether and many other organic solvents. It was first discovered by Hlasiwetz and Habermann in 1870, through the chemical oxidation of glucose. In the presence of the cyclic ester glucono-delta-lactone, gluconic acid exists in equilibrium in an aqueous solution. The salts of gluconic acid are called gluconates, where a gluconate ion is formed by gluconic acid in an aqueous solution at neutral pH. Gluconic acid, gluconate salts, and gluconate esters are abundant in nature as they can be produced by the oxidation of glucose. In an alkaline solution, the gluconate anion chelates Ca²⁺, Fe²⁺, Al³⁺, and other metals, including lanthanides and actinides.

Structure of Gluconic Acid

Gluconic acid is an organic compound that has a molecular formula of C₆H₁₂O₇ and the condensed structural formula HOCH₂(CHOH)₄COOH. The below figure is the structure of gluconic acid, where we can observe that it consists of a 6-carbon chain, with 5 hydroxyl groups placed in the same way as in the open-chained form of glucose, ending with the carboxylic acid group.

Structure of Gluconic Acid

Preparation of Gluconic Acid

Gluconic acid is a non-toxic compound that can be found naturally in honey, wine, fruits, etc. It is a carboxylic acid that can be formed by the oxidation of the first carbon of glucose with antiseptic and chelating properties. It can also be synthesized by hydrolysis of α-D-glucose with a mixture of bromide and sulfuric acid. It can also be prepared by gamma-irradiation of D-glucose. Gluconic acid is produced by oxidizing glucose in the presence of bromine water.

Preparation of Gluconic Acid

At present, gluconic acid is synthesized in commercial quantities by the fermentative oxidation of the aldehyde group in glucose from corn, which is carried out by Aspergillus niger, Aspergillus fumaricus, Aspergillus acetic, Penicillium chryrosogenum, and other pencillia. Gluconic acid and sorbitol are formed by the Cannizaro reaction on glucose, under alkaline conditions. It may also be prepared from the electrolytic oxidation of glucose in an alkaline medium. Or it can also be prepared by the chemical oxidation of glucose by a hypochlorite or hypobromite solution, or by directly oxidizing glucose in the presence of the palladium catalyst.

Physical Properties of Gluconic Acid

Chemical Properties of Gluconic Acid

• Calcium gluconate is formed by the neutralization of gluconic acid with lime or calcium carbonate.
• By heating ferrous carbonate with the proper quantity of gluconic acid in an aqueous solution, ferrous gluconate or iron (II) gluconate can be produced.
• Gluconic acid partially converts to an equilibrium mixture with gamma and delta gluconolactone in water. 

Uses of Gluconic Acid

• Gluconic acid is used for industrial cleaning, textile bleach stabilizing, aluminium processing, and as a chelating agent in cement set retarding.
• It is also used for metal surface treatment, cleaning products, personal care products, pharmaceuticals, and as a food additive.
• Calcium gluconate is used in the treatment of patients with hypocalcemia, and its gel is used in the treatment of burns from hydrofluoric acid.
• Quinine gluconate which is a salt of gluconic acid and quinine is used in the treatment of malaria.
• Ferrous gluconate, or iron (II) gluconate, injections have been proposed in the past to treat anaemia, which occurs due to iron deficiency.
• The gluconic acid aqueous solution is used as a medium for organic synthesis.

Hazards

Inhalation of dust irritates the nose and throat and contact with the eyes may cause mild irritation. It is a corrosive substance that may cause injury to the skin, eyes, and respiratory tract. 

FAQs on Gluconic Acid Formula

Question 1: Explain the preparation of gluconic acid.

Answer: 

Gluconic acid is a carboxylic acid that can be formed by the oxidation of the first carbon of glucose with antiseptic and chelating properties. It can also be synthesized by hydrolysis of α-D-glucose with a mixture of bromide and sulfuric acid. Gluconic acid and sorbitol are formed by the Cannizaro reaction on glucose, under alkaline conditions. It may also be prepared from the electrolytic oxidation of glucose in an alkaline medium.

Question 2: What is gluconic acid?

Answer: 

Gluconic acid is an organic compound that is also termed Dextronic acid and is one of the 16 stereoisomers of 2,3,4,5,6-pentahydroxyhexanoic acid. It was first discovered by Hlasiwetz and Habermann in 1870, through the chemical oxidation of glucose. In the presence of the cyclic ester glucono-delta-lactone, gluconic acid exists in equilibrium in an aqueous solution. The salts of gluconic acid are called gluconates, where a gluconate ion is formed by gluconic acid in an aqueous solution at neutral pH. Gluconic acid, gluconate salts, and gluconate esters are abundant in nature as they can be produced by the oxidation of glucose. 

Question 3: Mention some properties of gluconic acid.

Answer:

The IUPAC name of gluconic acid is D-Gluconic acid, and it has a molecular formula of C₆H₁₂O₇. It appears as a colorless to light yellow, clear, syrupy liquid and has a mild acid taste. It is very soluble in water, slightly soluble in alcohol, and insoluble in ether and many other organic solvents. Its molecular weight is 196.155 g/mol, and its density is 1.23 mg/mL.

Question 4: Mention some uses of gluconic acid.

Answer:

Gluconic acid is used for industrial cleaning, textile bleach stabilizing, aluminum processing, and as a chelating agent in cement set retarding. It is also used for metal surface treatment, cleaning products, personal care products, pharmaceuticals, and as a food additive. Calcium gluconate is used in the treatment of patients with hypocalcemia, and its gel is used in the treatment of burns from hydrofluoric acid.

Question 5: Mention some chemical properties of gluconic acid.

Answer:

Calcium gluconate is formed by the neutralization of gluconic acid with lime or calcium carbonate. By heating ferrous carbonate with the proper quantity of gluconic acid in an aqueous solution, ferrous gluconate or iron (II) gluconate can be produced. Gluconic acid partially converts to an equilibrium mixture with gamma and delta gluconolactone in water.

Question 6: Which salt of gluconic acid is used to treat malaria?

Answer:

Quinine gluconate which is a salt of gluconic acid and quinine is used in the treatment of malaria.