Pyrogallol

Pyrogallol

Names
Preferred IUPAC name Benzene-1,2,3-triol
Other names 1,2,3-Trihydroxybenzene Pyrogallic acid
Identifiers
CAS Number	87-66-1 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:16164 Y
ChEMBL	ChEMBL307145 Y
ChemSpider	13835557 Y
ECHA InfoCard	100.001.603
UNII	01Y4A2QXY0 Y
InChI InChI=1S/C6H6O3/c7-4-2-1-3-5(8)6(4)9/h1-3,7-9H Y Key: WQGWDDDVZFFDIG-UHFFFAOYSA-N Y InChI=1/C6H6O3/c7-4-2-1-3-5(8)6(4)9/h1-3,7-9H Key: WQGWDDDVZFFDIG-UHFFFAOYAT
SMILES Oc1cccc(O)c1O
Properties
Chemical formula	C6H6O3
Molar mass	126.11 g/mol
Density	1.45 g/cm3
Melting point	131 to 134 °C (268 to 273 °F; 404 to 407 K)
Boiling point	309 °C (588 °F; 582 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Pyrogallol is an organic compound with the formula C₆H₃(OH)₃. It is a white solid although samples are typically brownish because of its sensitivity toward oxygen. It is one of three isomeric benzenetriols.

It is produced in the manner it was first prepared by Scheele (1786): heating gallic acid. Presently gallic acid is obtained from tannin. Heating induces decarboxylation:

Because tannin is expensive, many alternative routes have been devised. An alternate preparation involves treating para-chlorophenoldisulphonic acid with potassium hydroxide, a variant on the time-honored route to phenols from sulfonic acids.

The aquatic plant Myriophyllum spicatum produces pyrogallic acid.

When in alkaline solution, it absorbs oxygen from the air, turning brown from a colourless solution. It can be used in this way to calculate the amount of oxygen in air, notably via the use of the Orsat apparatus.

One can find its uses in hair dying, dying of suturing materials and for oxygen absorption in gas analysis. It also has antiseptic properties. Pyrogallol was also used as a developing agent in black-and-white developers, but its use is largely historical except for special purpose applications. (Hydroquinone is more commonly used today.)