Ortho Phenylenediamine
A high-purity aromatic diamine, supplied as 1,2-phenylenediamine for benzimidazole condensation, azo dye chemistry and corrosion inhibitor manufacture.
What is Ortho Phenylenediamine?
Ortho Phenylenediamine, formally benzene-1,2-diamine, is a white to light brown crystalline solid carrying two amino groups on adjacent ring carbons. It darkens on exposure to air and light, which is why it is packed sealed and, where required, under nitrogen.
Having both amines side by side is what sets this isomer apart. The pair can close a ring across the two nitrogens: condensation with carboxylic acids or aldehydes gives benzimidazoles, and reaction with 1,2-diketones gives quinoxalines. The same pair also chelates metals and takes part in diazotization and coupling, so a single intermediate serves dye, agrochemical and corrosion inhibitor chemistry.
At Chelora Dyes, OPDA is crystallised and dried to a controlled melting range and low moisture, so condensation reactions run cleanly and the colour of the finished product stays consistent batch to batch.
- Appearance
- White to light brown
- Odour
- Faint, amine-like
- Solubility
- Water, alcohol, ether
- Function
- Condensation component
- Grade
- Technical / reagent
Benzene ring with two adjacent amino groups
- Molecular formulaC6H8N2
- Molecular weight108.14 g/mol
- IUPAC nameBenzene-1,2-diamine
- Functional groupsTwo primary aromatic amines
- CAS number95-54-5
Technical product information
Standard specification for Chelora Dyes' technical grade Ortho Phenylenediamine. Reagent-grade and low-colour specifications are available on request.
| Chemical name | Ortho Phenylenediamine |
|---|---|
| Synonyms | 1,2-Phenylenediamine, o-Phenylenediamine, OPDA, 1,2-Diaminobenzene |
| CAS number | 95-54-5 |
| Molecular formula | C6H8N2 |
| Molecular weight | 108.14 g/mol |
| Assay (purity) | ≥ 99.0% |
| Appearance | White to light brown crystalline flakes or powder |
| Melting range | 99–102°C |
| Boiling point | Approx. 256°C |
| Moisture content | ≤ 0.5% |
| Ash content | ≤ 0.1% |
| Solubility | Soluble in water, alcohol and ether |
| Packaging | 25 kg / 50 kg lined fibre or HDPE drums, nitrogen blanketed on request |
| Shelf life | 12 months in sealed original packaging |
Applications of Ortho Phenylenediamine
Benzimidazole chemistry
Condensation across the two amines builds the benzimidazole ring used in agrochemical and pharmaceutical actives.
Azo and direct dyes
Serves as a diazo and coupling component for brown, olive and violet shades in textile and leather dyeing.
Corrosion inhibitors
The chelating diamine pair underpins inhibitor and metal-treatment formulations for steel and copper.
High-performance polymers
Supplies the diamine unit for polybenzimidazole and related heat-resistant polymer chemistry.
Pharmaceutical intermediates
Used as a heterocycle building block where a fused nitrogen ring system is required.
Analytical reagents
Applied as a chromogenic and derivatising reagent in laboratory and diagnostic assay work.
Why choose Chelora Dyes
Consistent purity
Assay controlled at ≥99% with melting range and colour verified before dispatch.
Full documentation
COA, SDS, and regulatory data supplied with every shipment.
Protective packing
Sealed lined drums with nitrogen blanketing available to limit oxidation.
Technical support
Condensation, storage, and compliance guidance from our chemistry team.
Storage and guidelines
- Store in tightly sealed original packaging in a cool, dry, well-ventilated store.
- Keep in the dark — light and air both accelerate discolouration.
- Re-blanket part-used drums with nitrogen and re-seal them promptly.
- Segregate from oxidising agents, acids and acid chlorides.
- Use lined fibre, HDPE or stainless containers; avoid bare mild steel.
- Contain all spillage — the product is very toxic to aquatic life and must not reach drains.
Handling precautions
Ortho Phenylenediamine is harmful if swallowed or absorbed through the skin and is a recognised skin and respiratory sensitiser, so even brief contact should be avoided once someone is sensitised.
It also carries suspected carcinogen and mutagen classifications in several jurisdictions and is very toxic to aquatic organisms.
Control dust at weighing and charging points, use chemically resistant gloves, chemical splash goggles and protective clothing, and provide local exhaust ventilation wherever dust or vapour may be generated.
Refer to the current Safety Data Sheet for exposure limits, spill containment, disposal and first-aid measures before any handling operation.
Frequently asked questions
What is Ortho Phenylenediamine used for?
Its two adjacent amino groups make it a ring-forming building block. It condenses with acids, aldehydes and diketones to give benzimidazoles and quinoxalines, and it also serves as a diazo and coupling component in azo and direct dye manufacture, as a corrosion inhibitor intermediate and as an analytical reagent.
How does it differ from meta and para phenylenediamine?
All three isomers carry two amino groups, but only in the ortho isomer are they adjacent. That proximity is what allows a ring to close across the two nitrogens, which is why the ortho grade dominates benzimidazole chemistry while the meta and para grades are used mainly in dye coupling and polymer applications.
Why does the material darken in storage?
Aromatic diamines oxidise slowly on contact with air and light, and the oxidation products are strongly coloured. A shift from white towards light brown is normal and does not by itself indicate loss of assay. Keep drums sealed, cool and dark, and use nitrogen blanketing on part-used containers.
Is Ortho Phenylenediamine soluble in water?
Yes. Unlike the nitro intermediates it is appreciably soluble in water, and freely soluble in alcohol and ether, so condensation and coupling reactions can be run in aqueous or mixed media.
What purity do you supply?
Standard grade is supplied at a minimum assay of 99%, with moisture and ash held within tight limits. Higher assay and low-colour grades can be manufactured to order for reagent and pharmaceutical applications.
What packaging sizes are available?
25 kg and 50 kg lined fibre or HDPE drums, nitrogen blanketed on request, with larger volumes available on a scheduled supply basis.
How should it be stored, and for how long?
In sealed original packaging in a cool, dry, dark and ventilated store, away from oxidising agents and acids. Shelf life is 12 months from manufacture when storage conditions are maintained, and material held longer should be re-assayed before use.
Is it hazardous to handle?
Yes. It is harmful if swallowed or absorbed through the skin, is a skin and respiratory sensitiser, carries suspected carcinogen and mutagen classifications, and is very toxic to aquatic life. Control dust, avoid all skin contact, and review the current Safety Data Sheet before any handling operation.
Do you provide a Certificate of Analysis?
Yes. Each batch ships with a Certificate of Analysis and Safety Data Sheet covering assay, melting range, moisture, ash and appearance.
