Para Chloroaniline

Para Chloroaniline — 4-chloroaniline systematically — places its chlorine directly opposite the amino group. The position is the least sterically intrusive of the three and sits in full conjugation with the ring, which makes the amine readily available for acylation, condensation and diazotization while the para chlorine blocks the ring position most vulnerable to metabolic and chemical oxidation downstream. It is the most widely used of the monochloroanilines and the one with the broadest demand base.

Alone among the three isomers it is a solid at room temperature: pale yellow to light amber crystalline flakes with a mild sweetish aromatic odour, with technical grades running to tan or darker. The melting range of roughly 69–72.5 °C means it is traded as flakes or crystals, or handled molten. Two numbers matter for plant design and are frequently confused: the solid density is 1.43 g/cm³ at 20 °C, but molten material at 70 °C is 1.17 g/cm³, and it is the molten figure that governs tank and pump sizing. It also decomposes above 160 °C, so melt temperature must be controlled rather than simply raised.

Where it fits in the synthesis chain

Para Chloroaniline has the widest downstream range of the three isomers. In pharmaceuticals it is the precursor of chlorhexidine — and, being also its degradation product, a controlled impurity in chlorhexidine products; it feeds benzodiazepine chemistry through 2-amino-5-chlorobenzophenone, and the antiretroviral efavirenz. In crop protection it builds the phenylurea herbicides monuron and monolinuron, the benzoylurea insect growth regulators diflubenzuron and chlorbenzuron, the herbicide anilofos and the strobilurin fungicide pyraclostrobin. In colour it supplies Vat Red 32, Pigment Red 184, Pigment Orange 44, Pigment Green 10 and the Naphthol AS-E and AS-LB couplers.

Grades we supply

Chelora Chemicals offers Para Chloroaniline in technical grade (99%) and high-purity grade (99.5%+), both with a batch-wise certificate of analysis. Because of this product's regulatory status, orders are accompanied by the classification and restriction documentation described below, and we will ask about end use at the enquiry stage. That is a compliance requirement on our side, not a commercial qualification of your order.

Para Chloroaniline is made by reducing 4-nitrochlorobenzene, industrially by catalytic hydrogenation over Raney nickel at roughly 50–60 °C and elevated pressure, with reported yields of 90–95%. Tin or zinc with acid, and the iron and hydrochloric acid Béchamp reduction, are documented alternatives at smaller scale.

The nitro precursor is the dominant product of chlorobenzene nitration, which distributes roughly 63–65% to the para position — about twice the ortho fraction and some sixty times the meta. That is the single reason this isomer is the cheapest and most available of the three: it sits on the largest feedstock stream in the family.

A minor alternative route runs 1,4-dichlorobenzene with ammonia. Direct chlorination of aniline is not used, since it over-chlorinates. After reduction the amine is purified by distillation or recrystallisation and then flaked, drummed or kept molten for bulk transfer.

Handling a solid aniline: dust is the exposure route that matters

Because this product is a solid with a harmonised Category 1B carcinogen classification and a skin sensitisation endpoint, dust is the worst exposure form of the three isomers, and dust control at goods-in, charging and transfer is the governing engineering requirement. Molten transfer in insulated and traced lines removes the dust exposure but introduces a thermal one: the material decomposes above 160 °C, so melt temperature control and over-temperature protection are needed on heated vessels and lines.