Name: hiren
Message: i required to know what is the chemical structure of reactive red 3:1 as i am not able to get the latest color index database. so, request you to sir, please if you have than please give me.

I don't have ready access to the Colour Index, either. Have you tried a web search? It's easy to find the CAS number for this dye, which is 23211-47-4, and with that you can find a great deal of additional information. Brand names under which "reactive red 3:1" or "reactive red 3" are sold appear to include  Tulactiv Red P4BN and Brilliant Red K-2BP. The molecular formula is C25H15ClN7Na3O10S3, and the full chemical name is 2,7-Naphthalenedisulfonic acid, 5-((4-chloro-6-(phenylamino) -1,3,5-triazin-2-yl)amino)-4- hydroxy-3-((2-sulfophenyl)azo)-, trisodium salt.

The chemical structure for Colour Index reactive red 3 is listed online in US patent 4016149 as follows:

This structure is also given on page 190 of John Shore's excellent book, Cellulosics Dyeing, which is available for the very reasonable price of £9 when ordered directly from the Society of Dyers and Colourists in the UK. This dye is a 2-amino-4-chloro derivative of reactive red 1 (Procion Red MX-2B); the single chlorine makes it much less reactive, so it requires fixation temperatures of 70°C to 80°C.

I'm not sure what the notation "3:1" implies; perhaps that it's an impure mixture of reactive red 3 with a related molecule that gives the dye a slightly different hue. Could it be that the mixture contains some reactive red 1, given that it is described as being the chemical precursor for synthesis of reactive red 3? No, that is unlikely, since it is a dichlorotriazine dye; a mixture of two dyes of such different reactivity would be more difficult to work with.

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