Ortho Phenylene Diamine
A high-purity aromatic diamine supplied as flakes for benzimidazole synthesis, fungicide and pharmaceutical intermediates, dyes, and corrosion inhibitor manufacture.
What is Ortho Phenylene Diamine?
Ortho Phenylene Diamine — OPDA, or 1,2-phenylenediamine — is a crystalline solid carrying two amino groups on adjacent ring carbons. It is normally produced by reducing ortho nitroaniline.
Having both amines side by side is what makes the molecule valuable. The pair reacts with a single carbon electrophile to close a five-membered imidazole ring fused to the benzene ring, which is the standard route to benzimidazoles — the backbone of carbendazim-type fungicides, anthelmintic drugs, and high-temperature polybenzimidazole polymers.
At Chelora Chemicals, OPDA is crystallised and packaged with assay, melting range, and moisture held to specification, and handled to limit the air oxidation that darkens aromatic diamines faster than any other amine class.
- Appearance
- White to light brown crystalline flakes
- Odour
- Faint amine odour
- Solubility
- Soluble in water, alcohol, and ether
- Function
- Chemical intermediate
- Grade
- Technical
Formula diagram
Two amino groups on adjacent ring carbons
- Molecular formulaC6H8N2
- Molecular weight108.14 g/mol
- IUPAC name1,2-Phenylenediamine
- Functional groupsTwo primary aromatic amines
- CAS number95-54-5
Technical product information
Standard specification for Chelora Chemicals' technical grade Ortho Phenylene Diamine. Custom-grade and bulk specifications are available on request.
| Chemical name | Ortho Phenylene Diamine |
|---|---|
| Synonyms | OPDA, 1,2-Phenylenediamine, o-Phenylenediamine, 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 |
| Melting point | 100–103°C |
| Boiling point | 256–258°C |
| Flash point | > 150°C (closed cup) |
| Isomer content | ≤ 0.5% |
| Moisture | ≤ 0.5% |
| Packaging | 25 kg drums, 500 kg jumbo bags |
| Shelf life | 12 months in sealed original packaging |
Applications of Ortho Phenylene Diamine
Benzimidazole synthesis
Condensed with carbon electrophiles to close the fused imidazole ring at the heart of benzimidazole chemistry.
Fungicide intermediates
The starting amine for carbendazim-type agricultural fungicides.
Pharmaceutical intermediates
Feeds anthelmintic and other benzimidazole API routes.
Corrosion inhibitors
Used in the synthesis of benzimidazole and benzotriazole-type metal passivators.
Dyes & pigments
Applied in azo and sulfur dye intermediates requiring an ortho-diamine.
High-performance polymers
A monomer for polybenzimidazole resins used in high-temperature and membrane applications.
Why choose Chelora Chemicals
Every batch of Ortho Phenylene Diamine is manufactured, tested, and documented to a standard that formulators and process chemists can build on with confidence — from first sample to full production volume.
Consistent purity
Assay controlled at ≥99% with isomer content, colour, and melting range verified before dispatch.
Full documentation
COA, SDS, and regulatory data supplied with every shipment.
Flexible volumes
From 25 kg drums to 500 kg jumbo bags and full container loads.
Technical support
Process, handling, and compliance guidance from our chemistry team.
Storage and guidelines
- 01Store in tightly sealed original packaging under nitrogen where possible.
- 02Keep in a cool, dry, well-ventilated store, protected from air and light.
- 03Expect gradual darkening on exposure to air — aromatic diamines oxidise faster than monoamines.
- 04Segregate from strong oxidising agents, acids, and acid chlorides.
- 05Keep drums and bags palletised and dry; re-seal opened packaging immediately.
- 06Prevent any release to drains, surface water, or soil — the product is very toxic to aquatic life.
Handling precautions
OPDA is toxic if swallowed, in contact with skin, or if inhaled, is suspected of causing genetic defects, and may cause an allergic skin reaction. It is for industrial use by trained personnel only.
Aromatic diamines are potent skin sensitisers. Once a worker is sensitised, even very low subsequent exposures can trigger a reaction, so avoiding first contact matters more than tolerating small exposures.
Chemical-resistant gloves, coveralls, eye protection, and respiratory protection are required, with dust control at every bag or drum opening and charging point.
The product is very toxic to aquatic organisms with long-lasting effects. Contain all spills and dispose of waste through licensed routes.
Refer to the full Safety Data Sheet for exposure limits, health surveillance, spill response, and first-aid measures before use.
Frequently asked questions
What is Ortho Phenylene Diamine used for?
Its dominant use is benzimidazole synthesis: fungicides such as the carbendazim family, anthelmintic pharmaceuticals, corrosion inhibitors, and polybenzimidazole polymers. It also serves dye intermediate chemistry.
Why is the ortho isomer specifically needed for benzimidazoles?
The two amino groups must be on adjacent carbons to close a five-membered ring across them. The meta and para isomers cannot form that fused ring, so they are used for entirely different chemistry such as polymers and hair dye intermediates.
How is OPDA manufactured?
Usually by reducing ortho nitroaniline, either catalytically or with iron. Feed isomer purity carries through, which is why ONA and OPDA specifications are linked.
Why does the product darken so quickly?
Aromatic diamines oxidise readily in air, and the ortho arrangement makes the process particularly fast. Darkening is normal and usually does not affect assay, but sealed, nitrogen-blanketed, dark storage slows it considerably.
Is OPDA soluble in water?
Yes, unlike most of the aromatic amines in this range. It dissolves in water as well as alcohols and ether, which affects both its reaction chemistry and its environmental behaviour after a spill.
What does 'skin sensitiser' mean in practice?
It means a worker can develop an allergy after exposure, and thereafter react to concentrations far below any normal exposure limit. Prevention of first contact is the control strategy, which is why glove selection and dust containment are emphasised.
What purity do you supply?
Standard technical grade is supplied at a minimum assay of 99% with isomer content at or below 0.5% and moisture at or below 0.5%. Tighter specifications can be produced to order.
What packaging sizes are available?
25 kg drums and 500 kg jumbo bags, with full container loads for bulk users. Nitrogen-blanketed packaging is available for colour-sensitive applications.
Why is the shelf life shorter than for other solids in the range?
Because of oxidation. Twelve months is the practical window for maintaining colour and assay in sealed original packaging; material stored longer should be retested before use in a colour-sensitive process.
Is OPDA hazardous?
Yes. It is acutely toxic, a skin sensitiser, suspected of causing genetic defects, and very toxic to aquatic life with long-lasting effects. Trained personnel, containment, and full PPE are required per the Safety Data Sheet.
Do you provide a Certificate of Analysis?
Yes. Every batch ships with a Certificate of Analysis and Safety Data Sheet covering assay, isomer content, melting range, moisture, colour, and appearance.