Glyphosate

Glyphosate is a chemical compound from the phosphonate group. It is the biologically active main component of some broad-spectrum or total herbicides and has been marketed since the second half of the 1970s by Monsanto as an active ingredient under the name Roundup for weed control. Globally, it has been the most significant ingredient in herbicides by volume for many years. Glyphosate products are sold by more than 40 manufacturers.

Glyphosate is used in agriculture, horticulture, industry and private households. It has a non-selective effect on plants, which means that all plants treated with it die. Exceptions are crops that have been genetically modified to have herbicide resistance to glyphosate. Glyphosate products vary in salt formulation, medium (solution or granules) and active ingredient content. Examples of formulations include glyphosate ammonium salt and glyphosate isopropylammonium salt. The toxicity of finished formulated herbicides containing glyphosate, such as Roundup, may be higher than that of the pure active ingredient glyphosate by itself.

Compared to other herbicides, glyphosate usually has lower mobility, shorter lifetime and lower toxicity in animals. These are generally desirable properties for herbicides used in agriculture.

An intense public and scientific debate has developed on the question of whether glyphosate can cause or promote cancer. From 2015 onwards, this discussion intensified visibly. A European citizens' initiative with almost 1.1 million valid signatures called for a ban on glyphosate. This was prompted by the pending re-approval of glyphosate in the EU at the end of 2017 and its assessment as "probably carcinogenic" for humans by the International Agency for Research on Cancer (IARC).

This assessment was contradicted by other authorities and organizations, including the European Food Safety Authority (EFSA), which adopted the assessment of the German Federal Institute for Risk Assessment (BfR). Likewise, a Joint Meeting on Pesticide Residues (JMPR) of the World Health Organization (WHO), USEPA, Health Canada and the European Chemicals Agency (ECHA) concluded that glyphosate in food is not carcinogenic. These differences in findings are also attributed to different approaches to the assessment.

Production

Glyphosate was produced by at least 91 chemical companies in 20 countries in 2015. There are 53 producers in China alone, 9 in India and 5 in the U.S. The amount produced was estimated at 600,000 tons of glyphosate in 2008, 650,000 tons in 2011 and 720,000 tons in 2012. More than 40% of glyphosate is produced in China. In 2016, Chinese companies exported over 70,000 tonnes of glyphosate and formulations.

The patents on the production of glyphosate expired in 2000.

Extraction and presentation

Glyphosate can be obtained by reacting phosphorus trichloride with formaldehyde and water and then reacting the intermediate chloromethylphosphonic acid with glycine. Also possible is the preparation by reaction of diethyl phosphite (or phosphonic acid) with formaldehyde, glycine (or ethyl glycinate) and hydrogen chloride. A similar synthesis path is shown in the following reaction scheme, in which dimethyl phosphite is used instead of diethyl phosphite and the hydrochloric acid, which is not shown, causes the final ester cleavage at the phosphorus atom:

The preparation of glyphosate shown in the reaction diagram is used in the majority of industrial glyphosate production in China.