Phenidone

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title: "Phenidone" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["photographic-chemicals", "pyrazolidines", "lactams", "phenyl-compounds", "substances-discovered-in-the-19th-century"] topic_path: "general/photographic-chemicals" source: "https://en.wikipedia.org/wiki/Phenidone" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

| Watchedfields = changed | verifiedrevid = 464200287 | Name = Phenidone | ImageFile = phenidone.svg | ImageSize = | ImageName = | ImageFile1 = phenidone-spaceFill.png | ImageSize1 = | ImageName1 = | PIN = 1-Phenylpyrazolidin-3-one | OtherNames = | Section1 = {{Chembox Identifiers | SMILES = O=C2NN(c1ccccc1)CC2 | ChemSpiderID_Ref = | ChemSpiderID = 6823 | PubChem = 7090 | InChI = 1/C9H10N2O/c12-9-6-7-11(10-9)8-4-2-1-3-5-8/h1-5H,6-7H2,(H,10,12) | InChIKey = CMCWWLVWPDLCRM-UHFFFAOYAF | ChEMBL_Ref = | ChEMBL = 7660 | StdInChI_Ref = | StdInChI = 1S/C9H10N2O/c12-9-6-7-11(10-9)8-4-2-1-3-5-8/h1-5H,6-7H2,(H,10,12) | StdInChIKey_Ref = | StdInChIKey = CMCWWLVWPDLCRM-UHFFFAOYSA-N | CASNo = 92-43-3 | CASNo_Ref = | UNII_Ref = | UNII = H0U5612P6K | EINECS = 202-155-1 | Section2 = {{Chembox Properties | C=9 | H=10 | N=2 | O=1 | Appearance = Crystal leaflets or needles | Density = 1.188 +/- 0.06 g/mol | Solubility = 10 g/100 ml at 100 °C | Solubility1 = 10 g/100 ml (hot) | Solvent1 = ethanol | Solubility2 = practically insoluble | Solvent2 = diethyl ether | MeltingPtC = 121 | BoilingPtC = 288.88 | pKa = | Viscosity = | Dipole = | Section7 = {{Chembox Hazards | ExternalSDS = External MSDS | MainHazards = Harmful if swallowed | GHSPictograms = | GHSSignalWord = Warning | HPhrases = | PPhrases = |Section8={{Chembox Related | OtherFunction_label = | OtherFunction = }} --}}

Phenidone (1-phenyl-3-pyrazolidinone) is an organic compound that is primarily used as a photographic developer. It has ten to eighteen times the amount of efficiency and stability as Metol, capable of achieving the same level of development in both less time and at a lower concentration. It also has low toxicity and unlike some other developers, does not cause dermatitis upon skin contact. As a developer, Phenidone is typically used in conjunction with hydroquinone for black and white photography and performs better at lower pH levels (about 9.8-10.4). This is comparable to Metol whose working pH is approximately 10.3.

Phenidone is Ilford's trademark for this material, which was first filed on Feb. 24, 1953, but has since expired. Although the compound was first prepared in 1890; it was not until 1940 that J. D. Kendall, in the laboratories of Ilford Limited, discovered the reducing properties of this compound. Large scale production did not become feasible until 1951. It begun to be used by large companies, such as Agfa/Orwo, in the 1960s in place of Metol.

Phenidone functions as a reducing agent. It converts to the N-phenyl-hydroxypyrazole. It is oxidized in acidic conditions, contributing the electrons it loses to reduce silver halides such as those found in film: ::figure[src="https://upload.wikimedia.org/wikipedia/commons/c/c9/PhenidoneAction.svg" caption="Reaction of phenidone with silver bromide, as occurs in photographic development"] ::

Phenidone is also a dual cyclooxygenase/lipoxygenase inhibitor, capable of blocking the synthesis of arachidonic acid, which plays a role in causing inflammation in systemic inflammatory response syndrome and neuronal damage in kainic acid-induced seizures.

Preparation

Phenidone can be prepared by heating phenyl hydrazine with 3-chloropropanoic acid.

References

References

  1. Axford, A.J.. (January 1, 1954). "Phenidone—Part 1; The Mechanism of its Developing Action and its Super-additivity with Hydroquinone *". The Journal of Photographic Science.
  2. ''Merck Index of Chemicals and Drugs, 9th ed.'' monograph 7115
  3. "Trademark Status & Document Retrieval".
  4. Karlheinz Keller et al. "Photography" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2005, Wiley-VCH, Weinheim. {{doi. 10.1002/14356007.a20_001
  5. Spirin, M. G.. (2002). "Phenidone Oxidation during Photoinitiated Chemical Reduction of AgBr Nanocrystals in Water Pools of Reverse Micelles". Colloid Journal.
  6. Schroeder, Torsten. (March 2008). "Activity of the lipoxygenase inhibitor 1-phenyl-3-pyrazolidinone (phenidone) and derivatives on the inhibition of adhesion molecule expression on human umbilical vascular endothelial cells". Biologics: Targets and Therapy.
  7. Kim, Hyoung-Chun. (August 18, 2000). "Phenidone prevents kainate-induced neurotoxicity via antioxidant mechanisms". Brain Research.

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photographic-chemicalspyrazolidineslactamsphenyl-compoundssubstances-discovered-in-the-19th-century