Synthetic dyes made from sustainable chemicals

Industrial dyes come primarily from nonrenewable materials like coal tar. Plant-derived dyes present an attractive alternative but are expensive and resource intensive, and they often don’t work as well as their synthetic cousins. Seeking to make a more sustainable synthetic dye, chemist Mark Mascal and colleagues at the University of California, Davis, have synthesized yellow, orange, and red dyes using compounds derived from cellulose and lignin components (Angew. Chem., Int. Ed. 2019, DOI: 10.1002/anie.201911387). The team got the idea after reading a 1911 report of canary-yellow crystals that formed from the reaction of 5-(bromomethyl)furfural with barium carbonate in hot water (J. Chem. Soc., Trans., DOI: 10.1039/CT9119901193). Mascal’s group had been working with a related compound, 5-(chloromethyl)furfural (CMF), which can be made in high yield from raw biomass. The group found that CMF also produced yellow crystals in the presence of barium carbonate and hot water. Once they determined what molecule they had made, the researchers tweaked it to make several chromophores in the yellow to red range (two shown) that are capable of dyeing both natural and synthetic fibers. “The dirty image of the dyeing industry, along with the fact that no dyes are ever recycled, needs to be exposed,” Mascal says. “Hopefully this paper will motivate others to develop this field.”