Toward more sustainable fungicides.

De Sousa, R, C Thurier, C Len, Y Pouilloux, J Barrault and F. Jérôme. 2011. Regioselective functionalization of glycerol with a dithiocarbamate moiety: an environmentally friendly route to safer fungicides. Green Chemistry

Synopsis by Wim Thielemans,

Jul 07, 2011

A new approach devised by chemists promises to clean up the dirty business of making and using fungicides. The approach relies on a naturally-available source material called glycerol instead of the traditional metal-releasing compounds used today.

Fungicides kill or inhibit growth of molds, mildew and other fungi. Their use on food crops by the agricultural industry is omnipresent and has increased fourfold during the last 50 years. In 2007, fungicides accounted for $33 billion in sales.

With the growing population and the increased strain on food resources, the use of fungicides is set to continue to increase. This new work is a big step toward reducing the environmental impacts associated with producing and using the pesticides. It also opens the door to making other chemicals with the same starting chemical – the naturally-occurring glycerol.

Fungicides are generally prepared as water-soluble salts – in chemistry, salts are a  products made up of a positively and a negatively charged molecule that form the neutral salt. The salt products used for fungicide production also contain metals that contaminate soils, rivers and underground water. In addition, the breakdown products can be highly toxic.

It is thus very important to prepare safer fungicides through environmentally friendly processes.

A recent study published in the journal Green Chemistry reports a possible way to make safer, water-soluble fungicides without metal salts. The chemists describe making a specific class of fungicides – called dithiocarbamates – using a previously reported method that relies on glycerol instead of the salts. Glycerol forms part of plant oil molecules and is used as a sweetener and low fat filler in food and as a thickener in liqueur. It is also used in a variety of pharmaceutical and personal care products such as toothpaste, soap, mouthwash and cough syrup.

It turns out, the process is  more efficient and potentially cheaper than current methods. The chemical pathway releases only ethanol and CO2 as waste. All sulphur and nitrogen in the reactants was included in the final material, which is a major achievement. In addition, the researchers were able to scale up their process to produce larger quantities at one time.

The success of fungicides derived from this method is being tested in field studies on sunflower, wheat and soy crops. These studies will decide the real impact that this work can make on safer fungicide production.