Ortho Fluoro Aniline

Ortho Fluoro Aniline places a single fluorine on the ring position next to the amino group. Fluorine is the smallest substituent that meaningfully changes a molecule's electronics: it withdraws electron density strongly through the sigma framework while adding almost no steric bulk, so the amine's basicity drops and the ring's reactivity shifts without the nitrogen being crowded. In the ortho position it also blocks the adjacent ring site against later substitution and oxidation.

It is a liquid across any normal handling range, freezing only at −29 °C, and is colourless to yellow or orange when fresh, darkening to brown on storage. One number deserves attention before this product reaches your site: the closed-cup flash point is about 60 °C, considerably lower than the chlorinated anilines in this range, and low enough that some classifications treat it as a flammable liquid. It is appreciably more water-soluble than the chloroanilines at around 17 g/L at 20 °C.

Where it fits in the synthesis chain

This grade is a building block for fluorinated pharmaceuticals and agrochemicals, where the ortho fluorine is used to block metabolic oxidation at that ring position and to tune the basicity of the aniline nitrogen. Its most specific documented role is as the entry point to fused heterocycles — 7-fluoro-substituted quinolines and benzazoles — built by Skraup, Doebner–Miller and Friedländer-type cyclisations, in which the ortho relationship between the amine and the fluorine directs ring closure and fixes the fluorine adjacent to the ring fusion. It is also cited as a reagent in insecticide synthesis and as the precursor to the thermosensitive dye FH-102.

Grades we supply

Chelora Chemicals offers Ortho Fluoro Aniline in technical grade (98%) and high-purity grade (99%+), both with a batch-wise certificate of analysis. Fluorinated intermediates typically feed late-stage or regulated synthesis, so if you need a tighter specification on a particular impurity, state it at the enquiry stage and we will quote against it rather than against a house default.

Fluoroanilines are not made by fluorinating aniline — elemental fluorine is far too aggressive and unselective for that. The fluorine is installed one step earlier, on a nitro-activated ring, and the nitro group is then reduced to the amine.

The dominant industrial method is halogen exchange, commonly called Halex: a chloronitrobenzene is treated with spray-dried potassium fluoride in an anhydrous dipolar aprotic solvent such as DMSO or sulfolane, with a quaternary ammonium phase-transfer catalyst, at around 150–180 °C. The nitro group activates the ring towards nucleophilic aromatic substitution, allowing fluoride to displace chloride — a reaction that simply does not run on an unactivated ring. The resulting fluoronitrobenzene is then hydrogenated over palladium on carbon or Raney nickel to the aniline.

The classical alternative is the Balz–Schiemann reaction: the parent aniline is diazotized with sodium nitrite and fluoroboric acid to the aryldiazonium tetrafluoroborate, which is isolated and thermally decomposed to release nitrogen and boron trifluoride and deliver the aryl fluoride. It remains in use at smaller scale and for positions that Halex cannot activate, and continuous-flow variants have been developed to contain the hazardous diazonium intermediate.

Why the hydrogenation step needs care

Reducing a fluoronitrobenzene carries a risk the chlorinated series does not share in the same way: conditions that are too forcing can cleave the carbon–fluorine bond, destroying the very substituent the molecule was built for. Catalyst choice, hydrogen pressure and the rate at which the nitro compound is fed into the reactor are all set to complete the nitro reduction while leaving the C–F bond intact, and residual nitro compound is held low throughout to suppress azo and azoxy by-products.