Para Nitro Chloro Benzene (PNCB) 4-Chloronitrobenzene · CAS 100-00-5

What is Para Nitro Chloro Benzene (PNCB)?

Para Nitro Chloro Benzene, universally shortened to PNCB, is the para isomer of chloronitrobenzene, formula C₆H₄ClNO₂. At room temperature it is a pale yellow crystalline solid with a faint sweet odour, melting around 80–83 °C and insoluble in water.

The value of PNCB lies in having two reactive handles on the same ring: the nitro group can be reduced to an amine, and the chlorine is activated for nucleophilic substitution by the nitro group's electron-withdrawing effect. That combination lets downstream producers build p-aminophenol, p-phenylenediamine, p-anisidine and a wide range of other 1,4-disubstituted aromatics directly from it.

Commercially, PNCB is produced by nitration of chlorobenzene, which gives a mixture of ortho and para isomers that is separated by crystallisation and distillation. The para isomer, PNCB, is the larger-volume product and the one with the broadest downstream chemistry.

PNCB is a regulated, toxic chemical: it is classed as a probable human carcinogen and a cumulative-exposure hazard by several agencies, and is listed as a potential occupational carcinogen by NIOSH, which shapes how it must be handled, stored and documented.

Why PNCB specifically

• Two reactive positions. The nitro group reduces cleanly to an amine, and the para-chlorine undergoes nucleophilic aromatic substitution, both on the same ring.
• A route to p-aminophenol. Reduction and hydrolysis of PNCB is a key industrial route to p-aminophenol, the precursor to paracetamol (acetaminophen) and phenacetin.
• A route to p-phenylenediamine and p-anisidine. Substitution of the chlorine, followed by reduction of the nitro group, builds the diamine and amino-ether intermediates used across the dye and rubber-chemical industries.
• An agrochemical precursor. PNCB is used in the synthesis of organophosphate pesticide intermediates such as parathion.

How PNCB is Manufactured

PNCB is made on purpose by nitrating chlorobenzene, and the isomer split is what drives the separation train that follows.

• Nitration of chlorobenzene. Chlorobenzene is nitrated with a mixed acid (nitric acid and sulfuric acid) under controlled temperature, giving a mixture of ortho-nitrochlorobenzene (ONCB) and para-nitrochlorobenzene (PNCB), with a small amount of the meta isomer.
• Quenching and separation. The reaction mass is quenched, the spent acid is separated for recovery or disposal, and the crude nitrochlorobenzene oil is washed.
• Isomer separation. ONCB and PNCB are separated by fractional crystallisation (PNCB has the higher melting point) and/or distillation, since both isomers have real commercial value.
• Purification. The separated PNCB is further purified by recrystallisation or melt crystallisation to the target purity, typically 99.5% or better.
• Finishing. The purified solid is flaked, prilled or milled to the particle form the customer's process needs, then packed.

Typical Commercial Specification

Figures below are representative of commercial-grade PNCB. Tell us your downstream route and the grade you need, and we will advise on the specification to order against.

Physical & Chemical Properties

Behaviour in the process

PNCB's reactivity pattern is what downstream chemists are actually buying:

• Activated nucleophilic substitution. The para-nitro group activates the chlorine for substitution by amines, alkoxides and other nucleophiles, enabling routes to anisidines, phenetidines and diamines.
• Clean nitro reduction. Catalytic or chemical reduction converts the nitro group to an amine without disturbing the chlorine, a key step toward p-chloroaniline and, after further chemistry, p-aminophenol.
• Isomer sensitivity. Downstream selectivity and impurity profiles depend on how much ortho- and meta-isomer is carried into the reaction, which is why isomer purity is specified tightly.
• Combustible solid. PNCB is combustible and, like other nitroaromatics, can release toxic fumes including nitrogen oxides on burning.

PNCB, Its Isomers and Related Intermediates

PNCB is one of three nitrochlorobenzene isomers produced from the same nitration step, and buyers often need to distinguish between them and nearby intermediates.

Stated plainly: the choice between PNCB and ONCB is not a substitution decision but a structural one — each isomer leads to a different family of downstream products, and a process built around one cannot simply switch to the other.

Industries We Supply PNCB To

The same crystalline solid feeds a pharma intermediate plant, a dye-intermediate works and an agrochemical producer. What changes is the downstream chemistry and the documentation each requires.

Where PNCB is Used

PNCB is bought almost entirely as a chemical intermediate rather than a standalone product. These are the downstream chains our customers build from it.

In pharmaceutical intermediate manufacture

PNCB is reduced and hydrolysed to p-aminophenol, which is then acetylated to paracetamol or converted to phenacetin. Isomer purity matters here because ortho-isomer carry-over generates off-target impurities that complicate purification of the final active pharmaceutical ingredient intermediate.

In dye and rubber-chemical manufacture

Nucleophilic substitution of the chlorine with ammonia or an amine, followed by reduction of the nitro group, builds p-phenylenediamine — a workhorse intermediate for azo dyes, oxidative hair colourants and PPD-type rubber antiozonants.

Handling the isomer mixture

Because PNCB and ONCB are co-produced, some producers buy an isomer blend rather than pure PNCB when their downstream chemistry can tolerate it; others need isomer-pure material. Tell us which your process requires so we quote the right grade.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis, with isomer content reported alongside purity because it governs downstream selectivity.

• PNCB content — by gas chromatography, the primary grade measure.
• Isomer ratio (ortho, meta) — reported because carry-over changes downstream impurity profiles.
• Melting point — a fast indicator of purity and isomer content.
• Residual chlorobenzene — reported as an unreacted-feedstock impurity.
• Dinitrochlorobenzene — checked as an over-nitration by-product.
• Moisture — measured to limits relevant to handling and downstream reaction stoichiometry.
• Colour (molten) — an indicator of thermal history and trace contamination.

Common Process Problems & Likely Causes

When PNCB causes trouble, it is usually isomer carry-over, moisture or particle-size mismatch. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. HDPE-lined bags or drums, typically 25 kg net, palletised and shrink-wrapped for export.
• Particle form. Flake, prill or powder to customer requirement; confirm the form your process is designed around.
• Temperature control. Store below the melting point (80–83 °C) and away from direct sun and heat sources to avoid caking or melting in transit.
• Material compatibility. Avoid contact with strong oxidisers and strong reducing agents.
• Segregation. Keep apart from food, feed and incompatible chemicals in storage and transport, per its toxic classification.
• Shelf life. Stable in sealed, dry packaging; moisture ingress is the main degradation route for the solid.
• Transport classification. UN 1578, chloronitrobenzenes, Class 6.1 (toxic), packed per ADR, IMDG, IATA and DOT rules.

Hazards & Safe Handling

PNCB is a toxic chemical with cumulative-exposure effects. It is absorbed through skin as well as by inhalation, and is listed by NIOSH as a potential occupational carcinogen, which makes closed handling and exposure monitoring central to safe use.

• Toxicity and carcinogenicity. Exposure must be kept as low as technically possible, with closed handling, local exhaust ventilation and medical surveillance where required.
• Skin absorption. PNCB is absorbed through intact skin; OSHA's PEL carries a skin notation. Impermeable gloves and clothing are required.
• Occupational exposure limits. OSHA PEL is 1 mg/m³ (TWA, skin); confirm the limit applicable in your jurisdiction.
• Dust and combustibility. Avoid generating dust; the solid is combustible and nitroaromatic combustion can release toxic fumes including nitrogen oxides.
• PPE. Chemical-resistant gloves, goggles or a face shield, and respiratory protection appropriate to the dust or vapour exposure.
• Environment. Toxic to aquatic organisms; avoid release to waterways and follow local effluent and waste-disposal rules.

Regulatory & Compliance Notes

PNCB is a regulated toxic chemical with specific occupational and transport rules. Because obligations differ by territory and use, the notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser.

• GHS classification. Typically classified as acutely toxic, a suspected carcinogen and dangerous for the environment; the SDS carries the full hazard statements for your grade.
• Occupational exposure regulation. Many jurisdictions apply skin-notated exposure limits and require medical surveillance for workers with regular exposure.
• REACH and chemical inventories. Registered under EU REACH and listed on major chemical inventories.
• Dangerous goods transport. UN 1578, chloronitrobenzenes, Class 6.1 (toxic). ADR, IMDG, IATA and DOT requirements apply to packing, labelling and routing.
• HS code. Commonly declared under the nitrated-and-halogenated hydrocarbon heading; confirm the exact tariff line with your customs broker for your jurisdiction.
• Quality agreements. Pharma and agrochemical producers commonly expect documented isomer, moisture and colour limits and change control. Tell us what your agreement requires.

We Supply PNCB Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship PNCB from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, toxic-goods paperwork and freight so the material arrives ready to use.

• Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
• Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where toxic-goods rules and routing allow.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the Class 6.1 transport declaration issued as a complete set.
• Flexible volumes. From drum and bag trial quantities up to repeat bulk shipments on a supply contract.
• Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.

Buying PNCB from Chelora

We are an independent sourcing and supply partner. For PNCB that means settling three things at enquiry: the isomer purity your process tolerates, the particle form you need, and the toxic-goods documentation that moves it legally across your shipping lane.

• Documentation on every lot. Batch-specific COA with PNCB content, isomer ratio, melting point and moisture, plus SDS and Class 6.1 transport paperwork.
• Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
• Particle form. Flake, prill or powder, matched to your handling and dissolution requirements.
• Quantities. Drum and bag trial quantities through to full bulk shipments on contract supply.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related intermediates. ONCB, p-chloroaniline and p-nitroaniline alongside PNCB from one supplier.

How ordering works

• Send the enquiry. Isomer purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
• We quote. Price, lead time, particle form and a sample COA, normally within one working day.
• Qualify the supply. For first orders or pharma-grade applications, we share the analysis so your technical team can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
• Ship and document. Packed, labelled and loaded with the full export and Class 6.1 transport document set, and tracked through to arrival.

Related Nitroaromatics & Aniline Intermediates

Buyers of PNCB often source the ortho isomer or downstream aniline intermediates alongside it — dye and pharma producers typically buy several of these in the same programme. Consolidating them cuts freight cost and gives you a single point of contact for documentation.