Phenidone

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.^[1] It also has low toxicity and unlike some other developers, does not cause dermatitis upon skin contact.^[2] 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).^[1] This is comparable to Metol whose working pH is approximately 10.3.

Phenidone

Names
Preferred IUPAC name 1-Phenylpyrazolidin-3-one
Identifiers
CAS Number	92-43-3 Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL7660 Y
ChemSpider	6823 Y
ECHA InfoCard	100.001.960
EC Number	202-155-1
PubChem CID	7090
UNII	H0U5612P6K Y
CompTox Dashboard (EPA)	DTXSID1049433
InChI InChI=1S/C9H10N2O/c12-9-6-7-11(10-9)8-4-2-1-3-5-8/h1-5H,6-7H2,(H,10,12) Y Key: CMCWWLVWPDLCRM-UHFFFAOYSA-N Y InChI=1/C9H10N2O/c12-9-6-7-11(10-9)8-4-2-1-3-5-8/h1-5H,6-7H2,(H,10,12) Key: CMCWWLVWPDLCRM-UHFFFAOYAF
SMILES O=C2NN(c1ccccc1)CC2
Properties
Chemical formula	C9H10N2O
Molar mass	162.192 g·mol−1
Appearance	Crystal leaflets or needles
Density	1.188 +/- 0.06 g/mol
Melting point	121 °C (250 °F; 394 K)
Boiling point	288.88 °C (551.98 °F; 562.03 K)
Solubility in water	10 g/100 ml at 100 °C
Solubility in ethanol	10 g/100 ml (hot)
Solubility in diethyl ether	practically insoluble
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Harmful if swallowed
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H411
Precautionary statements	P264, P270, P273, P301+P312, P330, P391, P501
Safety data sheet (SDS)	External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Phenidone is Ilford's trademark for this material, which was first filed on Feb. 24, 1953, but has since expired.^[3] 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.^[4] 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:^[5]

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^[6] and neuronal damage in kainic acid-induced seizures.^[7]

Preparation

Phenidone can be prepared by heating phenyl hydrazine with 3-chloropropanoic acid.^[2]