o-Dianisidine is an organic compound with the formula [(CH₃O)(H₂N)C₆H₃]₂. A colorless or white solid, it is a bifunctional compound derived via the benzidine rearrangement from o-anisidine.

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O-Dianisidine

Names
Preferred IUPAC name 3,3′-Dimethoxy[1,1′-biphenyl]-4,4′-diamine
Other names 3,3'-dimethoxy-4,4’-benzidine
Identifiers
CAS Number	119-90-4
3D model (JSmol)	Interactive image
ChEBI	CHEBI:82321
ChEMBL	ChEMBL398363
ChemSpider	8104
ECHA InfoCard	100.003.960
EC Number	204-355-4
KEGG	C19231
PubChem CID	8411
RTECS number	DD0875000
UNII	MJY508JZXV
UN number	2811, 2431, 3077
CompTox Dashboard (EPA)	DTXSID3025091
InChI InChI=1S/C14H16N2O2/c1-17-13-7-9(3-5-11(13)15)10-4-6-12(16)14(8-10)18-2/h3-8H,15-16H2,1-2H3 Key: JRBJSXQPQWSCCF-UHFFFAOYSA-N
SMILES COC1=C(C=CC(=C1)C2=CC(=C(C=C2)N)OC)N
Properties
Chemical formula	C14H16N2O2
Molar mass	244.294 g·mol−1
Appearance	White solid
Density	1.178 g/cm3
Melting point	113 °C (235 °F; 386 K)
Boiling point	356 °C (673 °F; 629 K)
Solubility in water	60 mg/L
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H350
Precautionary statements	P201, P202, P264, P270, P281, P301+P312, P308+P313, P330, P405, P501
Flash point	206°C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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o-Dianisidine is a precursor to some azo dyes by formation of the bis(diazonium) derivative, which is coupled to diverse aromatic compounds. Some commercial dyes derived from o-dianisidine include C. I. Direct Blue 1, 15, 22, 84, and 98.^[1]

o-Dianisidine is also used in assaying activity of peroxidase in lab. The general reaction of a peroxidase is as follows.

${\displaystyle {\ce {ROOR'+{\overset {electron \atop donor}{2e^{-}}}+2H+->[{\ce {Peroxidase}}]{ROH}+R'OH}}}$

Where the ROOR' can be hydrogen peroxide, and the electron donor be o-dianisidine.

The manufacture and degradation of o-dianisidine, like other benzidene derivatives, has attracted regulatory attention.^[2] It is also used as a reagent in biochemistry in testing for peroxides.