D-Gluconic acid

July 08, 2019
I’m an excellent metal chelator.
What molecule am I?
Image of <small>D</small>-Gluconic acid 3D Image of <small>D</small>-Gluconic acid

D-Gluconic acid is the oxidized form of D-glucose (or dextrose), one of the fundamental building blocks for sugars, polysaccharides, and cellulose. Like glucose, it cyclizes in solution, in this case to form an ester (glucono-δ-lactone) rather than a hemiacetal.

Gluconic acid widely exists in nature, especially in fruits and in sucrose-containing substances such as honey. Early methods of synthesizing gluconic acid from glucose included hypobromite oxidation and alkaline hydrolysis. Now it is commercially produced by using microbes such as Aspergillus niger to oxidize glucose enzymatically.

Gluconate, gluconic acid’s conjugate base, is useful as a metal-chelating agent in alkaline solutions. It is a component of many cleaning products; and it is used to prevent formation of solids in dairy processing and beer brewing.

More recently, gluconic acid has been investigated as a chelating agent for extracting rare earths (lanthanides) from the fertilizer waste phosphogypsum.1 An estimated 100,000 t per year of valuable lanthanides are discarded in this waste product worldwide. Sulfuric acid is highly effective for recovering the rare earths, but a team led by Richard E. Riman of Rutgers University (New Brunswick, NJ) showed that gluconic acid and other bioacids are promising alternatives and would be considerably easier than sulfuric acid to treat for disposal.

1. Phosphogypsum does not contain phosphorus; it is a mostly gypsum (CaSO4·2H2O) waste product of phosphoric acid plants.

D-Gluconic acid hazard information

GHS classification*: skin corrosion/irritation, category 2
H315—Causes skin irritation Chemical Safety Warning
GHS classification: serious eye damage/eye irritation, category 2A
H319—Causes serious eye irritation Chemical Safety Warning

*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.

D-Gluconic acid fast facts

CAS Reg. No. 526-95-4
Empirical formula C6H12O7
Molar mass 196.16 g/mol
Appearance Colorless or white crystals
Melting point 131 ºC
Water solubility 316 g/L
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