3,4-Dichloroaniline

3,4-Dichloroaniline carries its chlorines meta and para to the amino group, leaving the nitrogen completely unhindered. That accessibility is the whole commercial story: the amine acylates cleanly, converts cleanly to the isocyanate, and does both at the scale and yield that high-tonnage herbicide manufacture requires. Where 2,6- is the isomer defined by what it resists, 3,4- is the one defined by how readily it reacts.

At room temperature it is a crystalline solid with a melting range of roughly 69–72 °C — the highest of the commercially traded isomers, and high enough that it stays a free-flowing solid through tropical transit without the melt-handling complications its 2,5- and 2,6- siblings bring. Pure material is white to light yellow; commercial grades are typically grey to light brown. It is practically insoluble in water at around 92 mg/L at 20 °C and dissolves in ethanol, acetone and other common organic solvents.

Where it fits in the synthesis chain

This isomer is used exclusively as a chemical intermediate, and it feeds the largest-tonnage downstream chain of any dichloroaniline. Through 3,4-dichlorophenyl isocyanate it becomes the phenylurea herbicides diuron, linuron and neburon. Acylated directly with propionyl chloride or propionic anhydride it becomes propanil, the anilide herbicide used at very large scale in rice. It also supplies the fungicide diethofencarb, the antimalarial chlorproguanil, the antibacterial triclocarban, and the 3,4-dichlorophenyl diazo component of disperse dyes for polyester.

Grades we supply

Chelora Chemicals offers 3,4-Dichloroaniline in technical grade (around 98% assay) for bulk herbicide synthesis and high-purity grade (99%+) where isomer carryover or trace metals matter. Both ship with a batch-wise certificate of analysis. For buyers running continuous acylation or isocyanate plant, consistency between batches usually matters more than a higher headline assay figure — tell our desk the tolerance band your process holds and we will quote against it.

Commercial 3,4-dichloroaniline is made by catalytic hydrogenation of 3,4-dichloronitrobenzene over precious-metal catalysts under pressure. The reaction is well established at large scale, which is part of why this isomer is the cheapest and most available of the family. The controlling concern is the same hydrodechlorination risk as elsewhere in the family: conditions that reduce the nitro group too hard also begin removing ring chlorine, producing mono-chloroaniline that carries forward into the herbicide product.

Iron and dilute acid reduction of the Béchamp type remains documented and is still used in some plants. It avoids pressurised hydrogen equipment at the cost of an iron sludge stream that has to be separated, dewatered and disposed of, so most current tonnage comes from catalytic hydrogenation.

After reduction the crude amine is washed and purified by vacuum distillation or recrystallisation to remove unreacted nitro compound, isomeric by-products and trace catalyst metal before drying and packing. The higher melting point makes this isomer the most straightforward of the family to isolate, dry and pack as a free-flowing solid.

Why isomer purity is set at the nitration stage

3,4-Dichloronitrobenzene comes from the nitration of 1,2-dichlorobenzene, and that step decides where the nitro group sits relative to the two chlorines. The substitution pattern is fixed upstream and cannot be corrected downstream, which is why the six isomers come from six distinct manufacturing streams. It is also worth noting that 3,4-DCA can form microbiologically from 3,4-dichloronitrobenzene in industrial wastewater, which is relevant to effluent monitoring at sites handling either compound.