Ortho Nitro Aniline Para Sulphonic Acid 2-Nitroaniline-4-sulfonic acid · CAS 616-84-2

What is Ortho Nitro Aniline Para Sulphonic Acid?

Ortho Nitro Aniline Para Sulphonic Acid, formally 2-nitroaniline-4-sulfonic acid (4-amino-3-nitrobenzenesulfonic acid), is a benzene ring carrying an amino group, a nitro group ortho to it, and a sulfonic acid group para to the amine, formula C₆H₆N₂O₅S. At room temperature it is a light yellow to pale yellow crystalline solid, decomposing above 300 °C rather than showing a sharp melting point, and is readily soluble in water because of the sulfonic acid group.

Its value as a building block comes from carrying three functional handles on one ring. The free amine is the diazotisable group that dye chemists couple onto a second component to build an azo chromophore; the sulfonic acid group stays on the finished molecule, giving the dye its water solubility and its substantivity to cellulosic and protein fibres; and the nitro group can either remain in the finished colour or be reduced downstream to build sulfonated phenylenediamine intermediates.

Commercially, it is produced either by sulfonating 2-nitroaniline with sulfuric acid or chlorosulfonic acid, or by aminating 4-chloro-3-nitrobenzenesulfonic acid, giving a high-purity nitroaniline sulfonic acid suitable for direct use as a diazo component.

It is generally handled and shipped as a non-flammable, non-explosive solid intermediate — a comparatively straightforward logistics profile for a nitroaromatic dye intermediate — though standard irritant and dust precautions still apply, and the current classification should always be confirmed against the SDS for your shipping lane.

Why Ortho Nitro Aniline Para Sulphonic Acid specifically

• A reliable diazo component. The free amine diazotises cleanly and couples to a wide range of components to build azo dyes and pigments in a well-understood, single-step process.
• Built-in water solubility. The sulfonic acid group carries through into the finished dye, giving it solubility and substantivity without a separate sulfonation step downstream.
• The specific substitution pattern dyestuff design needs. The ortho-nitro, para-sulfonic pattern relative to the amine gives a defined shade and fastness profile that a different isomer will not reproduce.
• A route into sulfonated diamines. Reduction of the nitro group gives 2,4-diaminobenzenesulfonic acid, a further building block in its own right.

How Ortho Nitro Aniline Para Sulphonic Acid is Manufactured

Ortho Nitro Aniline Para Sulphonic Acid is made on purpose through a dedicated sulfonation or amination sequence, so supply tracks installed nitro-chloro-benzene and sulfonation capacity rather than a generic aromatics feedstock stream.

• Starting material. 2-Nitroaniline, itself derived from the nitro-chloro-benzene value chain, is the common starting point.
• Sulfonation. The 2-nitroaniline is sulfonated under controlled conditions with sulfuric acid or chlorosulfonic acid, introducing the sulfonic acid group at the position para to the amine. Alternatively, 4-chloro-3-nitrobenzenesulfonic acid is aminated to the same target molecule.
• Neutralisation and isolation. The reaction mass is neutralised and the product is isolated and washed to remove inorganic salts and unreacted sulfonating agent.
• Drying and milling. The isolated solid is dried and milled to the particle size and moisture specification required by the customer's coupling process.
• Quality release. Assay, isomer purity and moisture are confirmed against specification before the batch is released.

Typical Commercial Specification

Figures below are representative of commercial-grade Ortho Nitro Aniline Para Sulphonic Acid. Tell us your downstream coupling chemistry and the grade you need, and we will advise on the specification to order against.

Physical & Chemical Properties

Behaviour in the process

Ortho Nitro Aniline Para Sulphonic Acid's reactivity pattern is what dye and pigment chemists are buying:

• Diazotisation. The primary amine diazotises readily under standard cold diazotisation conditions (sodium nitrite / mineral acid), the first step of azo dye manufacture.
• Azo coupling. The resulting diazonium salt couples to a wide range of coupling components to build the finished chromophore.
• Inherent sulfonation. Because the sulfonic acid group is already in place, no separate sulfonation step is needed downstream to achieve water solubility in the finished dye.
• Reducible nitro group. The nitro group can be reduced to an amine to access sulfonated phenylenediamine intermediates for further synthesis.

Ortho Nitro Aniline Para Sulphonic Acid and Related Nitroaniline Sulfonic Acids

ONA-PSA is one of several nitroaniline sulfonic acid isomers used as diazo components, and the choice between them depends on the substitution pattern the target shade needs.

Stated plainly: the choice of nitroaniline sulfonic acid is dictated by the shade and fastness the target dye needs — a route designed around this exact substitution pattern needs this specific isomer, and a different pattern requires a different starting material.

Industries We Supply Ortho Nitro Aniline Para Sulphonic Acid To

The same nitroaniline sulfonic acid feeds an azo dye manufacturer, a pigment producer and a textile-auxiliary formulator. What changes is the coupling partner and the documentation each requires.

Where Ortho Nitro Aniline Para Sulphonic Acid is Used

ONA-PSA is bought almost entirely as a diazo component. These are the downstream chemistries our customers use it for.

In dye and pigment synthesis

The amine is diazotised under standard cold conditions and coupled to a second aromatic component to build the finished azo colour. Isomer purity matters because a positional impurity can couple to give an off-shade by-product, which complicates purification and shade-matching of the final dye.

In downstream sulfonated-amine synthesis

Outside dyestuff chemistry, reduction of the nitro group gives sulfonated phenylenediamine intermediates used in further fine-chemical and specialty-colourant synthesis, where the pre-installed sulfonic acid group again saves a separate sulfonation step.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis, with isomer purity and moisture reported alongside assay because both affect downstream shade and coupling yield.

• ONA-PSA content — by HPLC or titration, the primary grade measure.
• Isomeric nitroaniline sulfonic acids — reported because positional isomer carry-over couples to a different shade.
• Moisture content — measured because excess moisture affects weighing accuracy and downstream diazotisation strength.
• Appearance and solution clarity — fast purity and identity checks.

Common Process Problems & Likely Causes

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

Packaging, Storage & Shipping

• Standard packing. HDPE/PP woven bags with liner, typically 25 – 50 kg net, with jumbo bags on contract supply.
• Moisture exclusion. Keep sealed and dry; excess moisture affects weighing accuracy and shelf life of the dry powder.
• Temperature control. Store at room temperature, away from direct sun and heat sources.
• Material compatibility. Standard dry-chemical storage practice; avoid contact with strong oxidisers and strong reducing agents.
• Shelf life. Stable in sealed, dry containers under normal storage conditions.
• Transport classification. Generally moved as a non-dangerous-goods solid on most trade lanes; confirm the current classification against the SDS for your specific shipping lane before booking.

Hazards & Safe Handling

Ortho Nitro Aniline Para Sulphonic Acid is a nitroaromatic amine intermediate. It is not classified as a flammable or explosive hazard under normal handling, but standard irritant, dust and good laboratory and plant practice precautions apply.

• Dust control. Use local exhaust ventilation or dust extraction when handling the powder in bulk, particularly during milling, weighing and charging.
• Skin and eye contact. Standard practice is chemical-resistant gloves and goggles; rinse thoroughly with water on contact.
• Inhalation. Use adequate ventilation when handling in open systems; a dust mask is recommended for bulk transfer.
• PPE. Chemical-resistant gloves, safety goggles and a dust mask as a baseline for routine handling.
• Environment. Avoid uncontrolled release to water; follow local effluent and waste-disposal rules.

Regulatory & Compliance Notes

Ortho Nitro Aniline Para Sulphonic Acid is a registered dye-intermediate chemical. 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 an irritant; the SDS carries the full hazard statements for your grade.
• REACH and chemical inventories. Registered under EU REACH and listed on major chemical inventories.
• Dangerous goods transport. Generally moved as a non-DG solid; confirm the current classification and any lane-specific requirements with your freight forwarder.
• HS code. Commonly declared under the aromatic amine derivatives heading; confirm the exact tariff line with your customs broker for your jurisdiction.
• Quality agreements. Dye and pigment producers commonly expect documented isomer purity and shade-reference data and change control. Tell us what your agreement requires.

We Supply Ortho Nitro Aniline Para Sulphonic Acid Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Ortho Nitro Aniline Para Sulphonic Acid from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation 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 as routing allows.
• Documentation. Commercial invoice, packing list, certificate of origin, COA and SDS issued as a complete set.
• Flexible volumes. From 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 Ortho Nitro Aniline Para Sulphonic Acid from Chelora

We are an independent sourcing and supply partner. For this product that means settling three things at enquiry: the purity and isomer tolerance your shade standard needs, the packing format, and the quantity you are buying.

• Documentation on every lot. Batch-specific COA with assay, isomer content and moisture, plus the current SDS.
• Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
• Quantities. Bag trial quantities through to larger bulk shipments on contract supply.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related dye-intermediate building blocks. 3,4,5-Trifluorobromobenzene, Para Fluoro Aniline and other fluorinated and nitroaromatic intermediates alongside this product from one supplier.

How ordering works

• Send the enquiry. 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, packing format and a sample COA, normally within one working day.
• Qualify the supply. For first orders or shade-critical 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 document set, and tracked through to arrival.

Related Nitroaniline & Dye Intermediates

Buyers of Ortho Nitro Aniline Para Sulphonic Acid often source other nitroaniline and fluorinated aryl intermediates alongside it. Consolidating them cuts freight cost and gives you a single point of contact for documentation.