2-Amino-4-Nitrophenol CAS 99-57-0

What is 2-Amino-4-Nitrophenol?

2-Amino-4-nitrophenol carries three different groups on one benzene ring: a hydroxyl, an amino group next to it, and a nitro group para to the hydroxyl. C₆H₆N₂O₃. That arrangement — an electron-rich pair in an ortho relationship, with a strong electron-withdrawing group opposite — is what makes it useful and what makes it coloured.

It is an orange to reddish-brown crystalline powder melting at about 142–146 °C, sparingly soluble in cold water and more soluble in alcohol and in alkali. The colour is intrinsic to the molecule rather than a sign of degradation, which catches out buyers accustomed to white aminophenols.

Its value in synthesis comes from the ortho amino-hydroxy pair, which closes readily into five-membered benzoxazole rings, and from the nitro group, which can be reduced to give a diaminophenol — the route to the photographic developer historically known as amidol.

Commercially it is a specialty intermediate serving dye and pigment manufacture, heterocyclic synthesis and, historically, hair colourant formulation. That last market is now restricted or prohibited in several major territories, so regulatory status by destination is a live commercial question rather than a footnote.

Why 2-amino-4-nitrophenol specifically

• An ortho amino-hydroxy pair. The two groups on adjacent carbons close cleanly into benzoxazoles and related five-membered heterocycles, which the para-substituted aminophenols cannot do.
• A nitro group ready for reduction. Reducing it gives 2,4-diaminophenol, used in photographic developer chemistry and as a further intermediate.
• Built-in chromophore. The donor-acceptor arrangement across the ring makes the molecule itself coloured, which is why it reaches dye and pigment chemistry directly rather than only as a precursor.
• Diazotisable amine. The primary aromatic amine diazotises and couples normally, opening azo colourant chemistry.

How 2-Amino-4-Nitrophenol is Manufactured

2-Amino-4-nitrophenol is made either by controlled nitration of a protected aminophenol or by selective reduction of a dinitrophenol. Selectivity is the whole challenge in both routes.

• Protection and nitration. 2-Aminophenol is acetylated to protect the amine, nitrated under controlled conditions to direct the nitro group para to the hydroxyl, then hydrolysed to free the amine. The standard route.
• Selective reduction of 2,4-dinitrophenol. Partial reduction of 2,4-dinitrophenol gives the amino-nitro compound. The difficulty is stopping at one nitro group rather than reducing both.
• Isomer control. Nitration can place the nitro group in more than one position, and the isomers are difficult to separate afterwards. Reaction conditions, not purification, are what determine isomer purity.
• Crystallisation and drying. The product is crystallised, washed free of acid and dried at controlled temperature. Residual acidity in the dried product causes problems on storage.

Typical Commercial Specification

Figures below are representative of standard commercial grade. Fine chemical grades with tighter isomer and metals limits are available — send us the specification you work to and we will quote against it.

Physical & Chemical Properties

Reactivity in practice

Three groups on one ring, each addressable. Which one you use decides which market the product serves:

• Ring closure to benzoxazoles. The ortho amino-hydroxy pair condenses with acids, aldehydes or orthoesters to give benzoxazoles — a ring system that appears across pharmaceutical and optical brightener chemistry.
• Reduction of the nitro group. Catalytic or chemical reduction gives 2,4-diaminophenol, used in photographic developers and as a further intermediate.
• Diazotisation and azo coupling. The primary amine diazotises and couples normally, giving azo colourants.
• Phenol chemistry. The hydroxyl, made more acidic by the para nitro group, ethers and esterifies, and dissolves readily in alkali for processing.
• Oxidative coupling. Historically the basis of its use in hair colourants, where it was oxidised in situ to build a shade — a use now restricted or prohibited in several territories.

2-Amino-4-Nitrophenol vs the Related Aminophenols and Nitrophenols

This family is defined entirely by where the groups sit on the ring. Two compounds with identical formulae can serve completely different markets, so substitution pattern is the first thing to confirm on any enquiry.

Stated plainly: 2-amino-4-nitrophenol and 4-amino-2-nitrophenol have the same molecular formula and swapped positions, and they are not interchangeable in any application. Confirm which one an enquiry means before quoting, because the names are easily transposed and the consequences of getting it wrong land in the customer's reactor rather than in ours.

Industries We Supply 2-Amino-4-Nitrophenol To

The same orange powder goes to a dye works, a heterocyclic synthesis plant and, where it remains permitted, a colourant formulator. What changes between them is the isomer specification and the regulatory documentation each destination requires.

Where 2-Amino-4-Nitrophenol is Used

2-Amino-4-nitrophenol is a specialty intermediate whose uses divide between colour and ring formation. These are the end uses our customers buy it for.

In benzoxazole and heterocyclic synthesis

The ortho relationship between the amino and hydroxyl groups is what makes this compound valuable to synthetic chemists: condensation with a carboxylic acid, aldehyde or orthoester closes the five-membered benzoxazole ring directly. The nitro group is then available for reduction or further substitution, giving a functionalised heterocycle in very few steps. This is why isomer purity matters more than almost anything else — an isomer in the feedstock cannot close the same ring, and what you get instead is a mixture.

In dye and pigment chemistry

Diazotisation and coupling give azo colourants, while the amino-hydroxy pair chelates metals to give mordant and metal complex dyes. The molecule is already coloured before any of that happens, which is unusual in an intermediate and means shade consistency between lots is something dye manufacturers assess directly rather than inferring from purity figures.

In colourant and imaging use

Reduction of the nitro group gives 2,4-diaminophenol, the photographic developer historically sold as amidol. Its use as an oxidative hair dye precursor is the part of this product's history that now requires the most care commercially — several major territories restrict or prohibit it in cosmetic applications, so the permitted status in your market must be confirmed before you design it into a formulation.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis. The methods behind the numbers are standard across the industry, and we are happy to share them or to work to your own in-house test protocol.

• Assay and isomeric purity — HPLC resolving the positional isomers, which is the figure that actually predicts how the material will behave in a ring closure.
• Melting range — a fast, revealing check. Isomers and residual starting material both depress and broaden it.
• Residual starting materials — unreacted 2-aminophenol and residual 2,4-dinitrophenol, each with its own downstream consequence.
• Free acidity — residual acid from the synthesis, which causes problems on storage rather than in the reaction.
• Loss on drying and sulphated ash — moisture and inorganic residue, both of which affect charge calculations.
• Shade comparison — assessed against a retained reference, because this material is intrinsically coloured and dye users judge it visually.

Common Process Problems & Likely Causes

When 2-amino-4-nitrophenol causes trouble in a plant, the cause is usually one of a short list of things. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. 25 kg net in fibre drums with polyethylene liners, or in lined HDPE bags, palletised and shrink-wrapped.
• Storage. Cool, dry, well-ventilated and dark, away from oxidising and reducing agents, acids and strong bases.
• Light protection. The material darkens further on prolonged light exposure. Keep it in its original opaque packing and out of direct light.
• Dust control. A coloured dust that stains skin, clothing and equipment, as well as being a health hazard. Contain transfers and clean spills promptly.
• Moisture. Keep liners tied and drums closed. Caked material is harder to charge accurately and may carry elevated free acidity.
• Materials of construction. Lined or stainless steel, or suitable plastics. Avoid prolonged contact with unlined mild steel.
• Shelf life. Typically 24 months in unopened original packing under those conditions. Beyond that, re-test assay and isomeric purity rather than assume.
• Transport classification. Generally shipped as a non-dangerous good for most modes; where a destination or carrier requires a classification it is handled as a toxic solid, organic, n.o.s., Class 6.1, Packing Group III. Confirm against the current SDS and the shipper's declaration for your destination and mode.

Hazards & Safe Handling

2-Amino-4-nitrophenol is harmful if swallowed, is a skin sensitiser and is treated as a suspected carcinogen in several classification systems. It must be handled by trained personnel under a proper risk assessment — the current SDS supplied with your consignment is the governing document.

• Sensitisation. Aromatic amines of this type are recognised skin sensitisers, and the hair colourant literature on this compound in particular is extensive. Preventing first contact matters far more than managing repeat contact.
• Carcinogenicity classification. Several jurisdictions apply a suspected-carcinogen classification to this substance, which brings specific workplace exposure obligations. Factor it into your own risk assessment rather than treating it as a labelling formality.
• Dust control. The main occupational exposure is airborne dust during charging and transfer. Handle in a closed system, under local exhaust ventilation, or with a dust-controlled charging arrangement.
• PPE. Chemical-resistant gloves, dust goggles, a suitable respirator where dust is generated, and overalls that stay on site — the dust stains and transfers readily.
• Nitroaromatic considerations. As a nitroaromatic with an aromatic amine, it carries the family's concerns about absorption through skin and about blood effects on significant exposure. Skin protection is not only about irritation.
• Incompatibilities. Strong oxidising agents, strong reducing agents, acid chlorides, nitrous acid and strong bases.
• Spill response. Avoid raising dust. Sweep or vacuum carefully into a labelled closed container, ventilate, and wash the area down — expect staining and allow time for it.
• Environment. Harmful to aquatic life. Do not allow to enter drains, surface water or groundwater. Dispose through a licensed chemical waste contractor.

Regulatory & Compliance Notes

2-Amino-4-nitrophenol is an established industrial chemical listed on the major national chemical inventories, but its cosmetic status differs sharply by territory. Because obligations differ by territory, volume and use, the notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser before importing.

• Cosmetic restrictions. Use in hair colourants and other cosmetic products is restricted or prohibited in several major territories, including under the EU Cosmetics Regulation. Confirm the current status for your market before designing it into a formulation — this is the single most important regulatory point about this product.
• Inventory status. Listed on the principal chemical inventories in the major importing regions. Ask us for the inventory confirmation relevant to your destination country.
• Carcinogen classification. The suspected-carcinogen classification applied in several jurisdictions triggers specific labelling and workplace exposure obligations.
• Import registration. Several territories require the importer to hold a registration or notification before a consignment lands. Start that process early — it is the most common cause of delay at destination.
• Hazard communication. Supplied with an SDS compliant with the format applicable to your region, and labelled in line with the GHS classification for the product.
• Dangerous goods. Generally not restricted for transport; where a classification applies it is a Class 6.1 toxic solid, Packing Group III. Confirm against the current SDS; declarations prepared for IMDG (sea) or IATA (air) as appropriate.

We Supply 2-Amino-4-Nitrophenol Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship 2-Amino-4-Nitrophenol from India to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, customs 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 Indian ports arranged where it suits the routing.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the end-use declaration this product requires issued as a complete set.
• Flexible volumes. A single drum for laboratory qualification, through LCL consolidations, up to repeat full container loads 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 2-Amino-4-Nitrophenol from Chelora

We are an independent sourcing and supply partner. For 2-amino-4-nitrophenol that means settling two things at enquiry: which isomer you actually mean, because 4-amino-2-nitrophenol is a different substance with the same formula, and what the material is for, because the cosmetic restrictions in several territories decide whether we can supply there at all.

• Documentation on every lot. Batch-specific COA including isomeric purity and residual starting materials, current SDS and TDS.
• Samples before commitment. Trial quantities for process qualification and shade matching ahead of a commercial order.
• Quantities. From a single 25 kg drum through to full container loads on contract supply.
• Isomer confirmation. We confirm the substitution pattern against the CAS number in writing at quotation, because the names in this family are easily transposed.
• Export experience. Packing, labelling and export documentation handled for sea and air freight.
• Related intermediates. 4-Aminophenol, salicylic acid and the wider pharmaceutical intermediate range from one supplier.

How ordering works

• Send the enquiry. Product, grade or pharmacopoeia standard, 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 and a sample COA, normally within one working day.
• Sample and qualify. For first orders or critical applications, we send a trial quantity so your lab can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Production and QC. Material allocated and released against a batch-specific COA, with a pre-shipment sample where the application calls for it.
• Ship and document. Packed, labelled and loaded with the full export document set, and tracked through to arrival.

Related Pharmaceutical Intermediates & Excipients

Buyers of 2-amino-4-nitrophenol usually source several of these alongside it. Consolidating them on one order cuts freight cost and gives you a single point of contact for documentation.