Para Nitrophenol
A high-purity nitrophenol, supplied as 4-nitrophenol for azo coupling, leather dye manufacture and onward reduction to p-aminophenol.
What is Para Nitrophenol?
Para Nitrophenol is a pale yellow crystalline solid carrying a hydroxyl group at C-1 and a nitro group directly opposite at C-4. Dissolved in acid it is close to colourless; add alkali and it turns an intense yellow, because the phenolate it forms is conjugated straight through to the nitro group.
That same conjugation is what makes it useful. The ring is activated where it matters for azo coupling, and the nitro group is a handle for later chemistry — reduced, it gives p-aminophenol, one of the highest-volume amines in the fine chemical industry.
At Chelora Dyes, PNP is crystallised and dried to a controlled melting range and low moisture, so coupling reactions strike at a reproducible shade and reduction downstream runs at predictable yield.
- Appearance
- Pale yellow crystals
- Odour
- Faint, phenolic
- Solubility
- Alkali, alcohol
- Function
- Coupling component
- Grade
- Technical / dye
Phenol ring with a para nitro substituent
- Molecular formulaC6H5NO3
- Molecular weight139.11 g/mol
- IUPAC name4-Nitrophenol
- Functional groupsPhenol, nitro
- CAS number100-02-7
Technical product information
Standard specification for Chelora Dyes' technical grade Para Nitrophenol. Custom-grade and bulk specifications are available on request.
| Chemical name | Para Nitrophenol |
|---|---|
| Synonyms | 4-Nitrophenol, p-Nitrophenol, PNP, 4-Hydroxynitrobenzene |
| CAS number | 100-02-7 |
| Molecular formula | C6H5NO3 |
| Molecular weight | 139.11 g/mol |
| Assay (purity) | ≥ 99.0% |
| Appearance | Pale yellow crystalline powder or needles |
| Melting range | 112–115°C |
| Boiling point | Approx. 279°C (decomposes) |
| Ortho isomer | ≤ 0.3% |
| Moisture content | ≤ 0.5% |
| Ash content | ≤ 0.1% |
| Solubility | Sparingly soluble in cold water; soluble in hot water, alcohol, acetone and dilute alkali |
| Packaging | 25 kg / 50 kg bags or fibre drums, 500 kg jumbo bags |
| Shelf life | 24 months in sealed original packaging |
Applications of Para Nitrophenol
Azo dye coupling
Used as a phenolic coupling partner in azo dye chemistry across yellow, amber and brown shade ranges.
Leather and paper dyes
Feeds dye formulations for leather finishing and paper colouration.
p-Aminophenol route
Reduction of the nitro group gives p-aminophenol for pharmaceutical and dye manufacture.
Agrochemical intermediates
Used as a starting material where a para-substituted nitrophenol core is required.
Fine chemical intermediates
Supplies a phenol and nitro pair for etherification, condensation and heterocycle chemistry.
Laboratory reagents
Applied as a pH indicator and as a substrate in enzyme assay and analytical work.
Why choose Chelora Dyes
Consistent purity
Assay controlled at ≥99% with melting range and isomer content verified before dispatch.
Full documentation
COA, SDS, and regulatory data supplied with every shipment.
Flexible volumes
From 25 kg bags to jumbo-bag bulk quantities.
Technical support
Coupling, reduction, and compliance guidance from our chemistry team.
Storage and guidelines
- Store in tightly sealed original packaging in a cool, dry, well-ventilated store.
- Keep out of direct sunlight and away from heat and ignition sources.
- Protect from moisture pickup — the powder can cake if exposed to humid air.
- Segregate from strong oxidising agents, reducing agents and alkalis.
- Re-seal bags promptly after use to preserve moisture and assay specification.
- Contain spillage and keep it out of drains and surface water.
Handling precautions
Para Nitrophenol is harmful by inhalation, ingestion and skin contact, and as a nitroaromatic it can cause methaemoglobinaemia on repeated or uncontrolled exposure.
It irritates skin, eyes and the respiratory tract, and it is toxic to aquatic organisms, so spillage must be contained rather than washed away.
Control dust at weighing, charging and any bulk handling point. Use chemically resistant gloves, eye protection and protective clothing, with local exhaust ventilation where dust may be generated.
Refer to the full Safety Data Sheet for exposure limits, spill containment, disposal and first-aid measures before use.
Frequently asked questions
What is Para Nitrophenol used for?
It is used as a coupling component in azo dye chemistry and as a general intermediate. Reduction of the nitro group gives p-aminophenol, which feeds pharmaceutical and dye manufacture, and the phenol itself is used in leather dyes, agrochemical synthesis and as a laboratory pH indicator and enzyme substrate.
Why does the solution turn deep yellow in alkali?
The phenol loses its proton in alkali to give the phenolate ion, which is strongly conjugated with the nitro group and absorbs visible light. The solid gives a colourless acidic solution and an intense yellow alkaline one, which is why it also serves as a pH indicator.
How does it differ from ortho nitrophenol?
In the ortho isomer the nitro group sits next to the hydroxyl and forms an internal hydrogen bond, which makes it volatile and steam distillable. In the para isomer the two groups are opposite, giving a much higher melting, non-volatile solid with different reactivity and downstream uses.
Is Para Nitrophenol soluble in water?
Sparingly in cold water, more freely in hot water, and very readily in dilute alkali as the phenolate. It also dissolves in alcohol, ether and acetone.
What purity do you supply?
Standard grade is supplied at a minimum assay of 99%, with a controlled melting range and moisture and ash held within tight limits. Higher assay grades can be manufactured to order.
What packaging sizes are available?
25 kg and 50 kg multiwall paper or HDPE-lined bags and fibre drums, with bulk supply available in 500 kg jumbo bags.
How should it be stored, and for how long?
In sealed original packaging in a cool, dry, ventilated store out of direct sunlight and away from strong oxidisers, reducing agents and alkalis. Shelf life is 24 months from manufacture when storage conditions are maintained.
Is it hazardous to handle?
Yes. It is harmful by inhalation, ingestion and skin contact, can cause methaemoglobinaemia on repeated exposure, irritates skin and eyes and is toxic to aquatic life. Control dust and review the current Safety Data Sheet before any handling operation.
Do you provide a Certificate of Analysis?
Yes. Each batch ships with a Certificate of Analysis and Safety Data Sheet covering assay, melting range, moisture, ash and appearance.
