Diphenylamine CAS 122-39-4

What is Diphenylamine?

Diphenylamine is a secondary aromatic amine with two phenyl rings on a single nitrogen, (C₆H₅)₂NH. Two aromatic rings pulling on the same lone pair makes it an extremely weak base — weaker even than aniline — and essentially unreactive as a nucleophile.

What it is instead is a radical scavenger, and an exceptionally good one. The N-H hydrogen is easily abstracted, and the resulting nitrogen radical is stabilised across both rings rather than being reactive. That is the textbook description of an antioxidant: something that interrupts a radical chain and then stops.

Physically it is a white to light-tan crystalline solid melting at about 53 °C, with a faint floral odour. It is practically insoluble in water and freely soluble in organic solvents, and it discolours on exposure to light and air.

Commercially, almost everything diphenylamine does comes from that radical-scavenging ability. Alkylated diphenylamines are among the most important antioxidants in lubricants and greases; diphenylamine derivatives are major antidegradants in rubber; and the same chemistry stabilises nitrocellulose-based propellants. It is also a dye intermediate and, in some jurisdictions, a post-harvest treatment for apples — a use with its own regulatory history.

Why diphenylamine specifically

• An exceptional radical scavenger. The N-H is easily abstracted and the resulting radical is delocalised across two rings, so it terminates an oxidation chain rather than propagating it.
• Thermally stable. It works at high temperature where phenolic antioxidants have already been consumed, which is why it dominates in engine oil and high-temperature grease.
• The route to 4-ADPA. Diphenylamine chemistry underpins 4-aminodiphenylamine, the intermediate for the para-phenylenediamine antiozonants used in essentially every tyre.
• Very weak base, so unreactive. Two aryl groups leave the nitrogen with almost no basicity, which means it sits quietly in a formulation rather than reacting with it.

How DPA is Manufactured

Diphenylamine is made from aniline by self-condensation. The reaction is conceptually simple and practically demanding, because the conditions needed also drive further arylation.

• Aniline condensation. Two molecules of aniline are condensed with loss of ammonia over an acid catalyst at elevated temperature and pressure. The equilibrium is unfavourable enough that conversion per pass is limited and unreacted aniline is recycled.
• Selectivity control. The same conditions that join two anilines will join a third, giving triphenylamine, and will drive ring alkylation to give carbazole and related heavies. Catalyst and residence time are what hold these back.
• Separation. Unreacted aniline is stripped and recycled, and the product is purified by distillation and crystallisation. Residual aniline is the characteristic trace and the one most often specified.
• Flaking and finishing. The purified material is flaked or prilled. Light and air exposure during handling cause discolouration, so finishing and packing are done to limit both.

Typical Commercial Specification

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

Physical & Chemical Properties

Reactivity in practice

Almost all of diphenylamine's commercial value comes from one behaviour, with substitution chemistry accounting for the rest:

• Radical scavenging. Donates its N-H hydrogen to a peroxy radical and forms a stabilised nitrogen radical, terminating the oxidation chain. This is the mechanism behind every antioxidant application.
• Alkylation. Reaction with olefins such as di-isobutylene or nonene gives the alkylated diphenylamines used as oil-soluble high-temperature antioxidants in lubricants and greases.
• Nitrosation and reduction to 4-ADPA. Diphenylamine chemistry leads to 4-aminodiphenylamine, the key intermediate for the para-phenylenediamine antiozonants used in tyre rubber.
• Condensation with acetone. Gives the acetone-diphenylamine condensation products used as rubber antioxidants.

Diphenylamine vs Aniline and the Aromatic Diamines

Aromatic amines behave quite differently from aliphatic ones, and the reason is the ring. The nitrogen lone pair is delocalised into the aromatic system, which makes these compounds far weaker bases and poorer nucleophiles than their saturated counterparts — and also gives them the toxicological profile that governs how they are regulated.

Stated plainly: aniline is a weak base because its lone pair is tied into the ring, which is why it behaves nothing like cyclohexylamine despite differing by only six hydrogens. Diphenylamine, with two rings on one nitrogen, is weaker still and works as a radical scavenger rather than as a base at all. The aromatic diamines are building blocks for isocyanates and high-temperature polymers. Across the whole class, health classification rather than chemistry is usually what decides whether a given compound can be used at all in a given market.

Industries We Supply DPA To

The same material leaves our warehouse for very different factories. What changes between them is the grade — residual aniline and colour in particular — and the documentation each sector expects.

Where DPA is Used

Diphenylamine is an antioxidant business above all. These are the end uses our customers buy it for, roughly in order of volume.

In lubricant antioxidants

This is the largest market and it rests on one property: thermal stability. A lubricant in a modern engine runs hot, and hindered phenol antioxidants — effective and cheap at moderate temperature — are consumed quickly above about 120 °C. Aminic antioxidants based on alkylated diphenylamine keep working well beyond that, which is why almost every high-performance engine oil, turbine oil and high-temperature grease contains one. Alkylating diphenylamine with di-isobutylene or nonene gives the oil solubility the application needs, and most commercial packages combine an aminic and a phenolic antioxidant to cover the whole temperature range.

In rubber antidegradants

The antiozonants that stop tyre sidewalls cracking are substituted para-phenylenediamines, and the route to them runs through 4-aminodiphenylamine, which is made from diphenylamine chemistry. These are among the highest-volume rubber chemicals in the world — essentially every pneumatic tyre contains one. Separately, condensing diphenylamine with acetone or styrene gives the octylated and styrenated diphenylamine antioxidants used where staining is acceptable.

As a propellant stabiliser

Nitrocellulose decomposes slowly in storage, releasing nitrogen oxides that then catalyse further decomposition — an autocatalytic process that limits safe shelf life. Diphenylamine scavenges those nitrogen oxides, interrupting the cycle, and has been the classical stabiliser for this purpose for over a century. This use is subject to controls on the propellant rather than on the diphenylamine, but buyers in this sector should expect end-use enquiry as a matter of course.

In post-harvest apple treatment

Superficial scald is a storage disorder of apples caused by oxidation products of alpha-farnesene in the skin. Diphenylamine applied post-harvest scavenges the radicals involved and prevents it. The regulatory position varies considerably: the treatment is permitted in some markets and has been withdrawn in others, and residue limits differ. Anyone buying for this use should confirm the current position at destination before importing — this is one application where the regulatory check genuinely comes first.

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 impurity profile — gas chromatography quantifying residual aniline, triphenylamine and carbazole heavies.
• Residual aniline — reported explicitly. It is more toxic and more volatile than diphenylamine itself, so it drives both exposure and odour.
• Melting point or crystallisation point — a fast, sensitive purity check. A depressed value flags aniline, moisture or heavies before any instrument confirms it.
• Colour of melt — APHA on melted material. Diphenylamine discolours on light and air exposure, and the colour carries into light-coloured finished products.
• Moisture — loss on drying or Karl Fischer, relevant to caking and to alkylation chemistry.
• Ash and metals — residue on ignition and iron, both relevant in lubricant additive service.

Common Process Problems & Likely Causes

When diphenylamine misbehaves 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 multi-wall paper bags with a polyethylene liner, palletised and shrink-wrapped.
• Bulk packing. 500 kg jumbo bags, and molten bulk in heated tankers for continuous users such as lubricant additive plants.
• Light exclusion. Diphenylamine discolours on light and air exposure. Opaque packaging and sealed storage are what keep the colour specification intact.
• Storage temperature. The melting point is near 53 °C, so a hot warehouse can soften or fuse bagged material. Store below that and away from direct sun.
• Materials of construction. Stainless steel or suitable lined vessels. Avoid copper, brass, bronze and aluminium.
• Oxygen and light exclusion. Aromatic amines darken rapidly on exposure to air and light — a surface oxidation effect rather than bulk decomposition, but one that matters where colour is specified. Nitrogen blanketing and opaque packaging are standard.
• Shelf life. Typically 12 months in unopened original packing under those conditions. Beyond that, re-test rather than assume.
• Environmental containment. Diphenylamine is very toxic to aquatic life. Bunding, drain protection and spill procedures should reflect that rather than treating it as an inert solid.
• Transport classification. Typically UN 3077, Environmentally hazardous substance, solid, n.o.s., Class 9, Packing Group III. Confirm against the current SDS for your destination and mode.

Hazards & Safe Handling

Diphenylamine is toxic by several routes and very toxic to aquatic life. It must be handled by trained personnel under a proper risk assessment. The classifications below are indicative — the current SDS supplied with your consignment is the governing document.

• Acute toxicity. Diphenylamine is classified as toxic by oral, dermal and inhalation routes — a step above most solid intermediates of its type. Exposure control should reflect that rather than treating it as a nuisance dust.
• Residual aniline. Free aniline in the product is more toxic and far more volatile than diphenylamine itself, and it is a skin-absorption and methaemoglobin hazard. Where the aniline figure is high, the exposure picture changes materially.
• Dust control. Handling flake or powder generates dust. Enclosed transfer and local exhaust at charging points are the standard controls, with respiratory protection appropriate to a toxic rather than a nuisance dust.
• Environmental containment. Very toxic to aquatic life with long-lasting effects. Bunding, drain protection and spill procedures are a priority, and effluent must be treated or consigned to licensed disposal.
• PPE. Chemical-resistant gloves, eye protection, protective clothing and respiratory protection where dust or molten material vapour is generated.
• Hot and molten material. Molten handling for bulk use introduces thermal burn risk and raises vapour exposure, including of any residual aniline. Treat it as a separate operation.
• Incompatibilities. Strong oxidising agents, strong acids and nitrating agents.
• First aid. Remove from exposure, remove contaminated clothing, wash skin thoroughly with soap and water, flush eyes for at least 15 minutes, and seek medical attention with the SDS to hand.

Regulatory & Compliance Notes

Diphenylamine is an established industrial chemical listed on the major national inventories, but it carries three separate regulatory dimensions: acute toxicity, severe aquatic toxicity, and a food-use history that differs sharply by territory. The notes below are orientation rather than legal advice; confirm your own position with your regulatory adviser before importing.

• Inventory status. Listed on the principal chemical inventories in the major importing regions. Ask us for the inventory confirmation relevant to your destination country.
• 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.
• Post-harvest and food use. Diphenylamine's use as an apple scald inhibitor is permitted in some markets and has been withdrawn in others, with differing residue limits where it is allowed. If your end use is agricultural or food-adjacent, confirm the current registration position and residue limits at destination before importing.
• Aquatic toxicity. Classified as very toxic to aquatic life with long-lasting effects, which affects transport classification, effluent handling and in some jurisdictions discharge permitting.
• Propellant end use. Where the material is destined for nitrocellulose propellant stabilisation, the controls attach to the propellant rather than the stabiliser, but end-use enquiry should be expected.
• Dangerous goods. Typically UN 3077, Environmentally hazardous substance, solid, n.o.s., Class 9, Packing Group III. Confirm against the current SDS; declarations prepared for IMDG (sea) or IATA (air) as appropriate.

We Supply DPA Worldwide

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

We are an independent sourcing and supply partner. For diphenylamine that means two things before quoting: establishing the residual aniline limit your application and your workplace can live with, and confirming that the end use is permitted at destination.

• Documentation on every lot. Batch-specific COA including residual aniline, current SDS and TDS.
• Samples before commitment. Trial quantities for process qualification ahead of a commercial order.
• Quantities. From a single 25 kg bag through to jumbo bags and molten bulk on contract supply.
• Export experience. Class 9 dangerous-goods documentation, packing and labelling handled for sea and road freight.
• Technical support. Direct access to people who know the chemistry, for questions on aniline limits, colour or alkylation behaviour.
• Related intermediates. Aniline, m-phenylenediamine, MDA, TDA and the wider aromatic amine range from one supplier.

How ordering works

• Send the enquiry. Product, grade or specification, 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 and dangerous-goods document set, and tracked through to arrival.

Related Aromatic Amines & Antioxidant Intermediates

Buyers of diphenylamine 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.