Fast Bordeaux GP Base

Fast Bordeaux GP Base (4-methoxy-2-nitroaniline) follows the naming convention of the azoic diazo base trade: a colour reference ("Bordeaux"), a supplier or grade code ("GP"), and "Base" signalling that this is the free-amine form sold to be diazotised by the dyehouse itself, rather than a pre-made, less stable diazonium salt. Unlike "2B Acid" elsewhere in this part of our range, this identification carries no meaningful ambiguity — every independent source we checked, including the Colour Index generic name "CI Azoic Diazo Component 1," agrees exactly on CAS 96-96-8.

In use, the dyehouse diazotises this base on-site with sodium nitrite and hydrochloric acid, then applies the resulting diazonium salt to cotton fabric that has already been padded with a Naphthol AS-type coupling component. The two react directly within the fibre to form an insoluble azo pigment — the classic "ice colour" or azoic dyeing process, valued for its wash- and light-fastness on cotton. We want to be honest that we could not confirm, in the sources checked, the exact Naphthol AS coupling partner or precise resulting shade documented for this specific base — azoic dyeing combination tables (Colour Index cross-reference charts) are the authoritative source for that pairing, and we'd recommend consulting one directly, or your dyehouse's own established recipe, rather than relying on a shade description from us.

Where it fits in the synthesis chain

We supply the free-base diazo component itself, for diazotisation at the dyehouse. We do not supply pre-diazotised material, Naphthol AS coupling components, or finished dyed fabric.

Grades we supply

98%+ is the standard dyehouse grade; isomeric and residual-nitro-compound purity matters for consistent diazotisation behaviour and shade reproducibility batch to batch.

Fast Bordeaux GP Base is made by nitration of p-anisidine (4-methoxyaniline), installing the nitro group at the position ortho to the amine, or alternatively by methoxylation of an appropriately nitrated chloroaniline precursor.

The nitration step requires careful temperature control to favour the correct regiochemistry and to limit over-nitration or oxidative by-products, since the base's diazotisation behaviour and the resulting dye's shade depend on a clean, single substitution pattern.

The crude product is purified by crystallisation and dried to the free-base solid traded commercially — importantly, as the stable amine, not as a diazonium salt, which would be far less stable to store and ship.

Why this is sold as the "base," not a ready-to-use diazonium salt

Diazonium salts are inherently less stable than the amines they're made from, and many decompose or lose potency on storage, especially in a warm climate. The azoic dyeing trade's standard practice — and ours — is to supply the stable free-base amine, which the dyehouse diazotises fresh, immediately before use, with sodium nitrite and acid under controlled cold conditions. This is why "Base" appears in the trade name: it tells the buyer what form they're receiving and what step they still need to perform before dyeing.