Anacardic acid isolated from cashew nut shells liquid: A potential precursor for the synthesis of anthraquinone dyes

The strategy for synthesis of anthraquinone based dyes from anacardic acid were developed. Five anthraquinone derivative dyes (1-hydroxyanthraquinone, 7-bromo-1-hydroxyanthraquinone, 1,7-hydroxyanthrquinone, 1-aminoanthraquinone and indanthrone) were synthesised from anacardic acid isolated from Cashew Nut Shells Liquid (CNSL). The novelty of the strategy is that the dyes have been synthesised from commercially inexpensive and renewable starting materials. The synthesised dyes were characterised by spectroscopic techniques such as FT-IR, NMR, HRMS and UV-Vis spectroscopy. The two synthesised anthraquinone dyes (1-hydroxyanthraquinone and 7-bromo-1-hydroxyanthraquinone) were tested on 100% polyester fabric while the synthesised indanthrone dye was tested on 100% cotton fabric. Reflectance spectrophotometer analysis of the dyed fabrics indicated good colour strength and wash fastness properties. This demonstrates that CNSL is a potential precursor in the synthesis of anthraquinone dyes.