Phenazine

Phenazine

Skeletal formula of phenazine
Ball-and-stick model
Names
IUPAC name Phenazine
Identifiers
CAS Number	92-82-0 Y
ChEBI	CHEBI:36674 Y
ChEMBL	ChEMBL119870 Y
ChemSpider	4593 Y
Jmol 3D model	Interactive image
PubChem	4757
UNII	6985IP0T80 Y
InChI InChI=1S/C12H8N2/c1-2-6-10-9(5-1)13-11-7-3-4-8-12(11)14-10/h1-8H Y Key: PCNDJXKNXGMECE-UHFFFAOYSA-N Y InChI=1/C12H8N2/c1-2-6-10-9(5-1)13-11-7-3-4-8-12(11)14-10/h1-8H Key: PCNDJXKNXGMECE-UHFFFAOYAM
SMILES n1c3c(nc2c1cccc2)cccc3
Properties
Chemical formula	C12H8N2
Molar mass	180.21 g/mol
Appearance	yellow to brown crystalline powder
Density	1.25g/cm3
Melting point	174–177 °C (345–351 °F; 447–450 K)
Boiling point	357.2 °C (675.0 °F; 630.3 K) at 760 mmHg
Solubility in water	insoluble in water
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Phenazine (C₁₂H₈N₂ or C₆H₄N₂C₆H₄), also called azophenylene, dibenzo-p-diazine, dibenzopyrazine, and acridizine, is a dibenzo annulated pyrazine and the parent substance of many dyestuffs, such as the toluylene red, indulines and safranines (and the closely related eurhodines). Phenazine crystallizes in yellow needles, which are only sparingly soluble in alcohol. Sulfuric acid dissolves it, forming a deep-red solution.

Synthesis

Classically phenazine are prepared by the reaction of nitrobenzene and aniline in the Wohl-Aue reaction). Other methods include:

• pyrolysis of the barium salt of azobenzoate
• oxidation of aniline with lead oxide
• oxidation of dihydrophenazine, which is prepared by heating pyrocatechin with o-phenylenediamine.
• oxidation of ortho-aminodiphenylamine with lead peroxide.

Derivatives

• The more complex phenazines, such as the naphthophenazines, naphthazines, and naphthotolazines, may be prepared by condensing ortho-diamines with ortho-quinones or by the oxidation of an ortho-diamine in the presence of α-naphthol, and by the decomposition of ortho-anilido-(-toluidido- et cetera)- azo compounds with dilute acids.
• If alkyl or aryl-ortho-diamines be used, azonium bases are obtained. The azines are mostly yellow in color, distill unchanged and are stable to oxidants. They add on alkyl iodides readily, forming alkyl azonium salts, anhydride formation also taking place between these hydroxylgroups. It dissolves in concentrated sulfuric acid with a yellowish-green fluorescence.
• The rhodamines, which are closely related to the phthaleins, are formed by the condensation of the alkyl metaaminophenols with phthalic anhydride in the presence of sulfuric acid. Their salts are fine red dyes. By the entrance of amino or hydroxyl groups into the molecule dyestuffs are formed. The mono-amino derivatives or eurhodines are obtained when the arylmonamines are condensed with orthoamino azo compounds; by condensing quinone dichlorimide or para-nitrosodimethyl aniline with monamines containing a free para position, or by oxidizing ortho-hydroxydiaminodipbenylamines. They are yellowish-red solids, which behave as weak bases, their salts undergoing hydrolytic dissociation in aqueous solution. When heated with concentrated hydrochloric acid the amino group is replaced by the hydroxyl group and the phenolic eurhodols are produced.

Diaminophenazine

File:Neutral red.png

Neutral red

The symmetrical diaminophenazine is the parent substance of the important dyestuff toluylene red or dimethyldiaminotoluphenazine. It is obtained by the oxidation of orthophenylene diamine with ferric chloride; when a mixture of para-aminodimethylaniline and meta-toluylenediamine is oxidized in the cold, toluylene blue, an indamine, being formed as an intermediate product and passing into the red when boiled; and also by the oxidation of dimethylparaphenylene diatnine with metatoluylene diamine. It crystallizes in orange-red needles and its alcoholic solution fluoresces strongly. It dyes silk and mordanted cotton a fine scarlet. It is known commercially as neutral red. For the phenazonium salts, see safranine. Phenazone is an isomer of phenazine, to which it bears the same relation that phenanthrene bears to anthracene.

Natural products

Many phenazine compounds are found in nature and are produced by bacteria such as Pseudomonas spp., Streptomyces spp., and Pantoea agglomerans. These phenazine natural products have been implicated in the virulence and competitive fitness of producing organisms. For example, the phenazine pyocyanin produced by Pseudomonas aeruginosa contributes to its ability to colonise the lungs of cystic fibrosis patients. Similarly, phenazine-1-carboxylic acid, produced by a number of Pseudomonas, increases survival in soil environments and has been shown to be essential for the biological control activity of certain strains.

Biosynthesis

Phenazine biosynthesis branches off the shikimic acid pathway at a point subsequent to chorismic acid. Two molecules of this chorismate-derived intermediate are then brought together in a diagonally-symmetrical fashion to form the basic phenazine scaffold. Sequential modifications then lead to a variety of phenazine with differing biological activities.

References

 This article incorporates text from a publication now in the public domain: