Pyrogallol

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Pyrogallol
Pyrogallol.svg
Pyrogallol-3D-balls.png
Pyrogallol powder.jpg
Names
Preferred IUPAC name
Benzene-1,2,3-triol
Other names
1,2,3-Trihydroxybenzene
Pyrogallic acid
1,2,3-Benzenetriol [1]
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.001.603 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 201-762-9
KEGG
PubChem CID
RTECS number
  • UX2800000
UNII
UN number 2811
  • InChI=1S/C6H6O3/c7-4-2-1-3-5(8)6(4)9/h1-3,7-9H Yes check.svgY
    Key: WQGWDDDVZFFDIG-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C6H6O3/c7-4-2-1-3-5(8)6(4)9/h1-3,7-9H
    Key: WQGWDDDVZFFDIG-UHFFFAOYAT
  • Oc1cccc(O)c1O
Properties
C6H6O3
Molar mass 126.11 g/mol
Density 1.453 g/cm3 (4 °C) [1]
Melting point 125.5 °C (257.9 °F; 398.6 K) [1]
Boiling point 307 °C (585 °F; 580 K) [1]
1.561 (134 °C) [1]
Structure [2]
Monoclinic
P21/n
a = 12.1144(11) Å, b = 3.7765(3) Å, c = 13.1365(12) Å
α = 90°, β = 115.484(1)°, γ = 90°
4
Hazards
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg
Warning
H302, H312, H332, H341, H412
P201, P202, P261, P264, P270, P271, P273, P280, P281, P301+P312, P302+P352, P304+P312, P304+P340, P308+P313, P312, P322, P330, P363, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

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

Contents

Production and reactions

It is produced in the manner first reported by Scheele in 1786: heating gallic acid to induce decarboxylation. [3]

Decarboxylation Gallic acid.svg

Gallic acid is also obtained from tannin. Many alternative routes have been devised. One preparation involves treating para-chlorophenoldisulfonic acid with potassium hydroxide, [4] a variant on the time-honored route to phenols from sulfonic acids. [5]

Polyhydroxybenzenes are relatively electron-rich. One manifestation is the easy C-acetylation of pyrogallol. [6]

Uses

It was once used in hair dyeing, dyeing of suturing materials. It also has antiseptic properties.

In alkaline solution, pyrogallol undergoes deprotonation. Such solutions absorb oxygen from the air, turning brown. This conversion can be used to determine the amount of oxygen in a gas sample, notably by the use of the Orsat apparatus. Alkaline solutions of pyrogallol have been used for oxygen absorption in gas analysis.

Use in photography

Pyrogallol was also used as a developing agent in the 19th and early 20th centuries in black-and-white developers. Hydroquinone is more commonly used today. Its use is largely historical except for special purpose applications. It was still used by a few notable photographers including Edward Weston. In those days it had a reputation for erratic and unreliable behavior, due possibly to its propensity for oxidation. It experienced a revival starting in the 1980s due largely to the efforts of experimenters Gordon Hutchings and John Wimberley. Hutchings spent over a decade working on pyrogallol formulas, eventually producing one he named PMK for its main ingredients: pyrogallol, Metol, and Kodalk (the trade name of Kodak for sodium metaborate). This formulation resolved the consistency issues, and Hutchings found that an interaction between the greenish stain given to film by pyro developers and the color sensitivity of modern variable-contrast photographic papers gave the effect of an extreme compensating developer. From 1969 to 1977, Wimberley experimented with the Pyrogallol developing agent. He published his formula for WD2D in 1977 in Petersen's Photographic. PMK and other modern pyro formulations are now used by many black-and-white photographers. The Film Developing Cookbook has examples. [7]

Another developer mainly based on pyrogallol was formulated by Jay DeFehr. The 510-pyro, [8] is a concentrate that uses triethanolamine as alkali, and pyrogallol, ascorbic acid, and phenidone as combined developers in a single concentrated stock solution with long shelf life . This developer has both staining and tanning properties and negatives developed with it are immune to the callier effect. It can be used for small and large negative formats.

The Darkroom Cookbook (Alternative Process Photography) has examples. [9]

Safety

Pyrogallol use, e.g. in hair dye formulations, is declining because of concerns about its toxicity. [10] Its LD50 (oral, rat) is 300 mg/kg. [3]

Isolated, pyrogallol was found to be extremely genotoxic in vitro, but certain compounds in the body may protect against its toxicity. [11] [12]

See also

Related Research Articles

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Benzoic acid is a white solid organic compound with the formula C6H5COOH, whose structure consists of a benzene ring with a carboxyl substituent. The benzoyl group is often abbreviated "Bz", thus benzoic acid is also denoted as BzOH, since the benzoyl group has the formula –C6H5CO. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, which was for a long time its only source.

<span class="mw-page-title-main">Ether</span> Organic compounds made of alkyl/aryl groups bound to oxygen (R–O–R)

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<span class="mw-page-title-main">Phenol</span> Organic compound (C6H5OH)

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<span class="mw-page-title-main">Gallic acid</span> 3,4,5-Trihydroxybenzoic acid

Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6H2(OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. It is a white solid, although samples are typically brown owing to partial oxidation. Salts and esters of gallic acid are termed "gallates".

<span class="mw-page-title-main">Aniline</span> Organic compound (C₆H₅NH₂); simplest aromatic amine

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<span class="mw-page-title-main">Metol</span> Reducing aromatic compound used as developing agent in black and white photography

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References

  1. 1 2 3 4 5 Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. p. 3.38. ISBN   9781498754293.
  2. ↑ Thakuria, Ranjit; Cherukuvada, Suryanarayan; Nangia, Ashwini (2012). "Crystal Structures of Pyrogallol, Its Hydrate, and Stable Multiple Z ′ Cocrystals with N-Heterocycles Containing Metastable Conformers of Pyrogallol". Crystal Growth & Design. 12 (8): 3944–3953. doi:10.1021/cg3003367.
  3. 1 2 3 Fiege, Helmut; Heinz-Werner, Voges; Hamamoto, Toshikazu; Umemura, Sumio; Iwata, Tadao; Miki, Hisaya; Fujita, Yasuhiro; Buysch, Hans-Josef; Garbe. "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. p. 1072. doi:10.1002/14356007.a19_313. ISBN   978-3527306732.
  4. ↑ Buzbee, Lloyd R. (1966-10-01). "Rearranged Products from the Reaction of Benzenesulfonic Acids with Caustic". The Journal of Organic Chemistry. 31 (10): 3289–3292. doi:10.1021/jo01348a042. ISSN   0022-3263.
  5. ↑ Magro, Angel A. Núñez; Eastham, Graham R.; Cole-Hamilton, David J. (2009-06-10). "Preparation of Phenolic Compounds by Decarboxylation of Hydroxybenzoic Acids or Desulfonation of Hydroxybenzenesulfonic Acid, Catalysed by Electron Rich Palladium Complexes". Dalton Transactions (24): 4683–8. doi:10.1039/B900398C. ISSN   1477-9234. PMID   19513476.
  6. ↑ Badhwar, I. C.; Venkataraman, K. (1934). "Gallacetophenone". Organic Syntheses. 14: 40. doi:10.15227/orgsyn.014.0040.
  7. ↑ Anchell, Stephen G.; Troop, Bill (1998). The Film Developing Cookbook. ISBN   978-0240802770.
  8. ↑ "510-PYRO". 510-PYRO.
  9. ↑ Anchell, Stephen, G. (2016). The darkroom cookbook (Fourth ed.). New York. ISBN   9781138959187. OCLC   938707611.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: multiple names: authors list (link)
  10. ↑ "Safety data for 1,2,3-trihydroxybenzene". Archived from the original on 2009-02-28. Retrieved 2009-03-05.
  11. ↑ "Cancer Biologists Find DNA-Damaging Toxins in Common Plant-Based Foods". Johns Hopkins Medicine. Retrieved 11 February 2024.
  12. ↑ "Compounds in Saliva and Common Body Proteins May Fend Off DNA-Damaging Chemicals in Tea, Coffee and Liquid Smoke". Johns Hopkins Medicine. Retrieved 11 February 2024.
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