Ortho Phenylene Diamine
Ortho Phenylene Diamine — OPD across the trade — is the gateway molecule to benzimidazole chemistry. Two amine groups on adjacent ring carbons is exactly the geometry needed to close a five-membered heterocycle, and that single structural fact puts OPD behind carbendazim and the benzimidazole fungicides, anthelmintic actives, rubber antioxidants, benzotriazole corrosion inhibitors and a long list of dyes.
Chelora Chemicals supplies OPD to agrochemical producers, pharmaceutical manufacturers, rubber chemical plants and dye houses worldwide, in bags and drums, with a batch COA and GHS safety data sheet on every consignment.
Product identity
- CAS Number
- 95-54-5
- IUPAC name
- Benzene-1,2-diamine
- Molecular formula
- C6H8N2
- Molecular weight
- 108.14 g/mol
- EC / EINECS
- 202-430-6
- MDL number
- MFCD00007721
- SMILES
- Nc1ccccc1N
- HS Code
- 2921 51*
* Confirm the exact HS heading with your customs broker — phenylenediamines sit under a different heading from the simple anilines, and destination tariffs vary.
What Ortho Phenylene Diamine is used for
Ortho Phenylene Diamine is an aromatic diamine with both amino groups on adjacent ring carbons. Almost everything interesting about it follows from that adjacency. Two nucleophilic nitrogens held a fixed distance apart will close onto a single carbon atom to form a five-membered ring, and depending on what that carbon comes from you get a benzimidazole, a benzotriazole, a quinoxaline or a benzimidazolone. No other phenylenediamine isomer can do this.
In practice OPD is a captive intermediate, and one that sits unusually far upstream: a single drum of it can end up in a fungicide, a dewormer, a tyre antioxidant, a cooling-water corrosion inhibitor or a hair dye, depending entirely on which one-carbon partner the buyer condenses it with. That breadth is why it trades steadily even when any one downstream market is soft.
Why the isomer matters
The three phenylenediamine isomers are chemically distinct and commercially unrelated. Substituting one for another does not lower the yield — it produces nothing at all, because the ring-closing geometry simply is not there:
- Ortho phenylene diamine (CAS 95-54-5) — this product. Amines at 1,2. The only isomer that closes a benzimidazole or benzotriazole ring.
- Meta phenylene diamine (CAS 108-45-2) — amines at 1,3. Used in azo dyes, epoxy curing agents and aramid chemistry.
- Para phenylene diamine (CAS 106-50-3) — amines at 1,4. The hair dye and antioxidant workhorse, and the aramid fibre monomer.
If your purchase order simply says "phenylenediamine", quote us the CAS number and we will confirm the correct material before the order is placed. We supply the other isomers and the related nitroanilines as well — see the full intermediate range.
Appearance and handling character
OPD ships as a white to light brown or tan crystalline solid melting around 100–104 °C. It is genuinely air- and light-sensitive, and this is the single most important practical fact about handling it. Exposed to air it oxidises through coloured quinoid and phenazine-type species, turning first pink, then red, then dark brown. Unlike the colour drift on a simple aniline, this is not merely cosmetic: it consumes assay, adds coloured impurities that carry into the finished heterocycle, and in a dye or pharmaceutical route it will cost you. Keep it sealed, keep it cool, and specify inert-gas packing if the material will sit before use.
| Parameter | Typical value |
|---|---|
| Appearance | White to light brown crystals / flakes |
| Assay (GC) | 99.0% min |
| Moisture (KF) | 0.5% max |
| Melting range | 100 – 104 °C |
| Total isomeric impurities | 0.5% max |
| Insolubles / residue | Reported per batch |
Important: the figures above are indicative of commercial grade material and are offered for planning only. The batch certificate of analysis is the governing document. If your process demands a tighter assay, a colour ceiling, a controlled moisture figure or limits on residual nitroaniline from the reduction step, send us the specification and we will quote against it rather than against a generic grade.
| Property | Value |
|---|---|
| Physical state | Crystalline solid at ambient |
| Melting point | ≈ 100 – 104 °C |
| Boiling point | ≈ 256 – 258 °C |
| Flash point | ≈ 136 °C |
| Relative density | ≈ 1.03 |
| Bulk density | ≈ 530 kg/m3 |
| pKa | ≈ 4.5 (conjugate acid) |
| Water solubility | Slightly soluble cold; soluble in hot water |
| Organic solubility | Freely soluble in alcohols, ether, chloroform |
| Stability | Air and light sensitive; darkens on exposure |
Physical constants compiled from public reference data for CAS 95-54-5 and rounded for readability. Published melting points vary between 98 °C and 105 °C across sources — treat them as orientation, not as a specification.
Where our customers put this molecule to work
OPD is one of the broadest intermediates we carry. Nearly every outlet below is a variation on the same move: close a ring across the two adjacent nitrogens, then substitute whatever the end market needs onto it.
Benzimidazole fungicides
The single largest outlet. Condensed with a cyanamide or carbamate partner, OPD closes into the benzimidazole core behind carbendazim and its relatives — systemic fungicides used across cereals, fruit, vegetables, rice and post-harvest treatment worldwide.
- Carbendazim and related actives
- Residual nitroaniline in the feed shows in the active
- Largest single source of global OPD demand
Pharmaceutical benzimidazoles
The benzimidazole ring is one of the most productive scaffolds in medicinal chemistry. OPD and its substituted derivatives feed anthelmintic actives, antiparasitic agents and a wide range of heterocyclic drug intermediates.
- Anthelmintic and antiparasitic chains
- Heterocyclic API intermediates
- Tight isomer and metals limits usually apply
Benzotriazole corrosion inhibitors
Treated with nitrous acid, the two amines close onto a nitrogen instead of a carbon to give benzotriazole — the standard copper and brass corrosion inhibitor in cooling water, metalworking fluids, antifreeze and dishwasher detergents.
- Copper and brass passivation
- Cooling water and metalworking chemistry
- Benzotriazole-class UV absorbers
Rubber & polymer additives
2-Mercaptobenzimidazole and the related heterocyclic antioxidants that protect elastomers against heat ageing are built from OPD. A steady, lower-visibility outlet that usually runs at technical rather than pharmaceutical purity.
- Heterocyclic antioxidant synthesis
- Tyre and technical rubber compounding
- Looser colour tolerance than pharma use
Dyes, pigments & diagnostics
A long-established colour intermediate and oxidation base, and — in a much smaller but high-value niche — the chromogenic substrate used with horseradish peroxidase in immunoassay work, where purity expectations are far above technical grade.
- Oxidation dye bases and azo chemistry
- Quinoxaline and heterocyclic colourants
- Diagnostic-grade material on request
Contract & scheduled supply
Fungicide manufacture is seasonal and OPD does not sit well in a warehouse for years. Most buyers want quantity released against a production plan rather than in one shipment. We hold inventory and release it to your schedule.
- Annual contracts with scheduled call-off
- Fresher material at the point of use
- Second source held in reserve
How we supply Ortho Phenylene Diamine
Chelora Chemicals is a supplier and sourcing partner, not a manufacturer. We own no diamine plant — and for an oxidation-sensitive intermediate like this one, that independence works in your favour. We are never obliged to push you whatever a captive unit happens to be running, or whatever has been sitting longest in a warehouse.
Instead we place your order with whichever qualified producer best matches your assay, your colour requirement, your price point and your delivery window.
On OPD specifically we pay attention to age and storage history, not just the COA. A certificate issued eight months ago against material that has since sat in a hot shed tells you very little about the drum you are opening.
- Specification read against the CAS first. We confirm you need 95-54-5 and not the meta or para isomer before we quote a price — they are not interchangeable in any route.
- Batch COA shared before dispatch. You approve the assay, moisture, colour and impurity profile against your own spec while the material is still in our warehouse.
- Inert-gas packing on request. Where colour and assay retention matter, we arrange nitrogen-blanketed drums so the material reaches you in the condition it left the plant.
- Manufacturing date disclosed. For an air-sensitive solid, how old the lot is matters as much as what the certificate says. We tell you, unprompted.
- Pre-shipment samples for qualification. New account or new source, your R&D team runs a cyclisation trial before the full quantity ever moves.
- Export machinery handled in-house. Hazard classification, UN-approved packing, labelling, freight booking and customs paperwork are ours to manage.
- Consolidation onto one bill of lading. Ship OPD alongside other intermediates from our range — one invoice, one shipment, one counterparty.
Packed to keep air out
With an oxidation-sensitive solid, pack format is not only a cost question — it decides what condition the material is in when your operator opens it. Tell us how it will be charged at your end and we will quote accordingly.
Multi-wall bags with liner
Laminated multi-wall bags with a sealed inner liner, palletised and shrink-wrapped. Economical, and the smaller unit means less material exposed once a pack is opened.
Fibre & HDPE drums
UN-certified drums with liner — the preferred format for OPD on longer sea transits. Far better protection against air ingress and moisture pick-up than bagged material.
Inert-gas packing
Drums sealed under a nitrogen headspace where colour and assay retention matter — dye, diagnostic and pharmaceutical-chain buyers should ask for this as standard.
Samples & trial packs
Laboratory samples and pilot quantities dispatched by courier so your R&D team can qualify the grade before committing to campaign volume.
Incoterms to suit you
Quoted on the Incoterm your purchasing team works to. Ocean, air and road freight arranged end-to-end with documentation filed before booking.
Campaign despatch
Because fresher is better on this product, we hold contracted quantity and release it against your production calendar instead of landing a year's requirement at once.
Handle this as a toxic, sensitising diamine
OPD is acutely toxic by ingestion, a recognised skin sensitiser, and carries suspected mutagenicity and carcinogenicity entries in widely published classifications. Several occupational hygiene bodies list it as a suspected human carcinogen with a low exposure limit. The summary below is orientation only — the safety data sheet supplied with your consignment is the authoritative document and should govern your risk assessment, PPE selection, exposure monitoring and emergency planning.
Classified hazards
H301Toxic if swallowed.H332Harmful if inhaled.H317May cause an allergic skin reaction.H319Causes serious eye irritation.H341Suspected of causing genetic defects.H351Suspected of causing cancer.H410Very toxic to aquatic life with long lasting effects.
Hazard statements reflect the GHS classification commonly published for CAS 95-54-5. Supplier classifications differ in detail; always read the SDS issued with your specific batch, and note that some occupational hygiene bodies set an exposure limit as low as 0.1 mg/m³ with a suspected-carcinogen notation.
Spill & emergency orientation
Plan your response before the pallet arrives, not after a bag splits. The points below are orientation for your emergency planners — sections 4, 5 and 6 of the SDS are the authoritative instructions and should be posted at the point of use.
- Sweep, do not hose. The material is very toxic to aquatic life. Collect spilled solid mechanically into a labelled, closed container; never wash it to a drain.
- Suppress dust. Dry sweeping of a fine solid generates an inhalable aerosol — use vacuum collection or dampen carefully in line with the SDS.
- Take sensitisation seriously. H317 means a worker who reacts once may react far more strongly next time. A skin exposure is a reportable event, not a wash-and-carry-on.
- Have the SDS with the casualty. Aromatic amines can affect the blood, and the treating clinician needs the product identity and CAS number in hand.
- Dispose as regulated waste through a licensed contractor, in line with your local chemical waste regulations.
Storage
- Cool, dry, dark and sealed. This is the product where storage conditions genuinely change what you receive. Air and light drive oxidation that costs assay, not just appearance.
- Inert headspace for long storage. Nitrogen blanketing is the difference between a white solid and a brown one after six months in a warm store.
- Keep well below the melting point. At around 100 °C the melting point is comfortably above transit temperatures, but heat still accelerates the oxidation chemistry.
- Segregate from oxidising agents, strong acids and nitrites. As a reactive aromatic diamine it is incompatible with a wide range of reagents.
- Shelf life is typically 12–24 months in sealed original packing under these conditions — and materially shorter once a pack has been opened. Re-assay before use after long storage.
Handling & PPE
- Design exposure out. Closed transfer and mechanical charging first, local exhaust ventilation second, PPE last. With a suspected carcinogen and a sensitiser, the hierarchy of control matters.
- Skin protection is the priority. Chemical-resistant gloves and coveralls, not splash protection — and a firm rule against continuing work in contaminated clothing.
- Respiratory protection where dust may be generated, particularly when emptying bags or breaking a caked drum, per your own exposure assessment.
- Eye protection and an accessible eyewash and safety shower at all charging points — H319 applies.
- Never discharge to drain or watercourse. H410 applies — collect spills as solid waste and dispose of them as regulated chemical waste.
Transport
OPD moves as regulated cargo. We classify each consignment, apply UN-approved packaging and labelling, and file the dangerous-goods declaration before the booking is made. The applicable UN number, class and packing group are stated on your shipping documents and SDS — ask us for the current DG paperwork when you plan the shipment.
What travels with every consignment
A chemical shipment is only as good as the file that travels with it. Verifying what the source plant sends is precisely the work you are buying from a supplier.
Certificate of Analysis
Batch-specific assay by GC, moisture by Karl Fischer, appearance, colour, melting range and impurity profile — checked against your purchase specification before we release the goods.
Manufacturing date & lot age
For an air-sensitive diamine this belongs on the same page as the assay. We disclose the production date and the storage history of the lot we are offering you, not just its certificate.
GHS Safety Data Sheet
Full 16-section SDS in GHS format covering hazards, exposure controls, handling, storage, spill response, toxicology and disposal — issued in the language your destination requires.
Dangerous Goods Declaration
UN number, hazard class, packing group and IMDG or IATA declaration prepared and filed before the container is booked, with correctly marked and labelled packaging.
Third-party inspection
SGS, Intertek or Bureau Veritas sampling and inspection arranged on request before loading, giving you independent verification of what actually ships.
Retained & pre-shipment samples
Pre-shipment samples carry the same COA as the commercial lot, so what your laboratory qualifies is exactly what arrives. Retention samples held against the batch.
One diamine, four rings
What makes OPD commercially unusual is that the same molecule closes into four different heterocyclic families depending only on what you hand it. Understanding which ring you are building tells you which impurity in the feed will hurt you. The routes below are the general industrial pattern, not a process disclosure.
Start with the 1,2-diamine
Two nucleophilic nitrogens on adjacent carbons, held at a fixed distance. Everything downstream is a variation on closing a ring across that pair.
Choose the partner
A one-carbon electrophile — cyanamide, urea, an acid, an aldehyde or a carbamate — gives a benzimidazole. Nitrous acid gives a benzotriazole. A 1,2-dicarbonyl gives a quinoxaline.
Cyclise
The ring closes, usually with water or ammonia leaving. This is the step where any competing amine in the feed produces a structurally similar by-product you will spend money separating.
Substitute and finish
The heterocycle is carbamoylated, alkylated or otherwise elaborated into the finished fungicide, drug substance, inhibitor or antioxidant, then purified to market grade.
Why feed quality carries through the whole route
The cyclisation step is unforgiving in a specific way: it consumes both nitrogens at once, so anything that has already reacted with one of them is simply lost material, and anything that mimics the diamine produces a near-identical ring:
- Oxidation products are the big one. Partially oxidised OPD cannot cyclise cleanly, and the coloured quinoid species it forms carry into the finished heterocycle. On this product, colour really is a purity indicator.
- Residual nitroaniline from an incomplete reduction upstream is a mono-amine — it cannot close a ring, consumes reagent and shows up in the impurity profile of the active.
- Isomeric diamines from the meta or para series cannot cyclise at all. They pass through the reactor, dilute your charge and end up in the mother liquor.
- Residual water competes with the ring-closing partner in several of these condensations and can depress yield noticeably in a tight batch.
That chain of consequences is the reason we quote against your written specification rather than a generic "99% technical" grade, and the reason the batch COA and the lot age are both shared for approval before dispatch rather than sent with the invoice.
| Reacted with | Ring formed & typical outlet |
|---|---|
| Cyanamide / carbamate | 2-Aminobenzimidazole Carbendazim-type fungicides |
| Carbon disulfide | 2-Mercaptobenzimidazole Rubber antioxidants |
| Nitrous acid | Benzotriazole Corrosion inhibitors, UV absorbers |
| 1,2-Dicarbonyl compounds | Quinoxalines Dyes and pharmaceutical scaffolds |
Upstream, OPD itself is normally made by catalytic reduction of the corresponding nitroaniline — which is why residual nitro compound is the impurity worth specifying. We supply that precursor too; see the full intermediate range.
What actually moves the price of this intermediate
OPD is not a commodity with a screen price. Knowing what drives the quote helps you time a purchase and read whether an offer is realistic.
Fungicide seasonality
Benzimidazole fungicide manufacture runs ahead of the spray season, so OPD demand peaks months before any product reaches a field. Northern and southern hemisphere campaigns stagger the load through the year.
- Quote early for pre-season tonnage
- Spot buying at peak costs materially more
- Contracted call-off smooths the exposure
Upstream feedstock
The route back to OPD runs through chlorobenzene, the nitration chain and a hydrogenation step. Movements in benzene, chlorine, nitric acid, ammonia and hydrogen all feed through within a quarter or so.
- Nitration and hydrogen costs set the floor
- Catalyst cost weighs on the reduction step
- We flag feedstock-driven moves in the quote
Specification tier
Diagnostic and pharmaceutical-chain material with colour ceilings and tight impurity limits prices well above technical grade destined for rubber chemicals. Paying for a spec you do not need is a common and avoidable cost.
- Tell us the end use, not just the purity
- Technical grade suits rubber and inhibitor outlets
- We will say when a tighter spec is unnecessary
Lot age and freshness
Uniquely among the anilines we carry, aged stock on this product is worth less — and some sellers price it as if it were not. A cheap offer on a two-year-old lot is rarely the bargain it appears to be.
- Ask for the manufacturing date, always
- Check colour on arrival, not at point of use
- Scheduled release beats bulk stockpiling
Freight & DG surcharges
This is regulated cargo, so ocean freight carries a hazardous surcharge and space is tighter than for general cargo. Destination and Incoterm move landed cost as much as the ex-works price does.
- Compare on landed cost, not ex-works
- DG space books out ahead of peak season
- We quote FOB, CIF, CFR or DDP as you prefer
Source availability
A plant turnaround, an environmental inspection or a monsoon disruption can take capacity offline at short notice. Single-sourced buyers feel this hardest.
- We hold a second qualified source on this line
- Qualify the alternate before you need it
- Ask us about dual-source contracts
| If your end use is… | Specify |
|---|---|
| Benzimidazole fungicides | High assay, low residual nitro compound, controlled moisture |
| Pharmaceutical chain | As above, plus colour ceiling, metals and residues reported |
| Benzotriazole inhibitors | High assay; colour less critical than for colour work |
| Rubber antioxidants | Technical grade; looser colour tolerance acceptable |
| Diagnostic / laboratory | Small pack, high purity, inert packing, full analytical pack |
Not sure which column you are in? Describe the reaction you are running and our technical desk will recommend the grade — including telling you when a cheaper specification would do the job just as well.
Support that goes beyond shipping the drum
What our technical desk will do
- Match a grade to your reaction. Tell us which ring you are closing and we will recommend the specification — and say so plainly when a tighter, costlier grade would add nothing.
- Be honest about colour. On most anilines we will tell you colour drift is cosmetic. On OPD we will not: we will tell you what the colour is likely costing you and what packing prevents it.
- Advise on handling and storage for your site conditions — an open bag in a humid plant behaves very differently from a nitrogen-blanketed drum in a cool store.
- Review your specification before it goes into a contract, so you are not locked into a limit that no plant can consistently hit.
Regulatory & compliance notes
- Carcinogen and mutagen entries. Where a suspected-carcinogen classification triggers obligations at your site — substitution review, exposure monitoring, health surveillance, record retention — confirm what applies before the first delivery.
- Import controls vary by destination. Because OPD feeds pesticide manufacture, some jurisdictions apply registration, licensing or end-use declaration requirements. We check the destination rules before quoting, not after you have raised the PO.
- Chemical inventory listings differ between regions. Confirm your obligations under the applicable inventory regime for your import volume — we will supply the identity data you need for that filing.
- Cosmetic and article restrictions apply to phenylenediamines in several markets. If your end use is anywhere near consumer articles, your regulatory team should confirm the position before you commit.
None of the above is legal advice — your own regulatory affairs team owns the final compliance position for your import and your workplace. What we commit to is giving you accurate product identity data, an honest statement of the hazard classification and complete documentation to work from.
From enquiry to delivered drum
Send the specification
Product name or CAS 95-54-5, the assay, colour and impurity limits you work to, quantity, pack preference and destination port.
Receive a firm quote
Pricing, lead time, packing, lot age and Incoterm confirmed in writing within 24 hours — our sourcing desk is staffed around the clock.
Qualify and approve
Sample dispatched if you are qualifying a new source. Batch COA and manufacturing date shared for your approval before the material is released.
Ship and track
DG classification filed, freight booked, export documents issued, and the consignment tracked through transit and clearance to your plant.
What buyers ask us about Ortho Phenylene Diamine
The material has turned pink or brown. Is it still usable?
Can I substitute meta or para phenylenediamine?
What purity do you normally supply?
Should I ask for nitrogen-blanketed packing?
What is the minimum order quantity?
How long does delivery take?
How should we store it, and what is the shelf life?
What are the specific health precautions we should plan for?
Is this a dangerous good? What paperwork comes with it?
- Batch certificate of analysis, with the manufacturing date
- GHS-format safety data sheet
- Dangerous-goods declaration with UN number, class and packing group
- Commercial invoice, packing list and bill of lading or airway bill
- Certificate of origin and any destination-specific forms
Do you supply to my country?
Do you manufacture this yourself?
Can you hold stock against a production plan?
Request pricing on Ortho Phenylene Diamine
Send your required assay, colour ceiling, quantity, pack format and destination port. Our sourcing desk is available 24 hours a day, 7 days a week, and comes back with pricing, lead time, lot age and packing options — whether that is a single trial bag or a contracted programme for the season.