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Issue 3, 1999
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Monobromoindigos: a new general synthesis, the characterization of all four isomers and an investigation into the purple colour of 6,6′-dibromoindigo

Abstract

A new general synthesis of all four isomers of monobromoindigo is outlined, the synthesis of 4-, 6- and 7-bromoindigo being described for the first time. All four monobromoindigos as well as indigo and the historically important 6,6′-dibromoindigo (Tyrian purple) have been characterized by 1H NMR spectroscopy of their N,N′-bis(trifluoroacetyl) derivatives, by FT-IR and FT Raman spectroscopy, and by their visible absorption spectra in solution and as dyes on wool. The absorption spectra of the dyes have been calculated by molecular mechanics (MM+) and semiempirical MO (PM3) methods. The purple colour of wool dyed with 6,6′-dibromoindigo is thought to be due to the interaction of the π systems of two parallel molecules that are brought together by van der Waals attraction between the bromine atoms.

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Article information


New J. Chem., 1999,23, 323-328
Article type
Paper

Monobromoindigos: a new general synthesis, the characterization of all four isomers and an investigation into the purple colour of 6,6′-dibromoindigo

R. J. H. Clark and C. J. Cooksey, New J. Chem., 1999, 23, 323
DOI: 10.1039/A808562E

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