Investigation of the mechanism of chlorination of glyphosate and glycine in water.
The chlorination reactions of glyphosate and glycine in water were thoroughly studied. Utilizing isotopically enriched (13C and 15N) samples of glycine and glyphosate and 1H, 13C, 31P, and 15N NMR spectroscopy we were able to identify all significant terminal chlorination products of glycine and glyphosate, and show that glyphosate degradation closely parallels that of glycine. We have determined that the C1 carboxylic acid carbon of glycine/glyphosate is quantitatively converted to CO2 upon chlorination. The C2 methylene carbon of glycine/glyphosate is converted to CO2 and methanediol. The relative abundance of these two products is a function of the pH of the chlorination reactions. Under near neutral to basic reaction conditions (pH 6-9), CO2 is the predominant product, whereas, under acidic reaction conditions (pH < 6) the formation of methanediol is favored. The C3 phosphonomethylene carbon of glyphosate is quantitatively converted to methanediol under all conditions tested. The nitrogen atom of glycine/glyphosate is transformed into nitrogen gas and nitrate, and the phosphorus moiety of glyphosate produces phosphoric acid upon chlorination. In addition to these terminal chlorination products, a number of labile intermediates were also identified including N-chloromethanimine, N-chloroaminomethanol, and cyanogen chloride. The chlorination products identified in this study are not unique to glyphosate and are similar to those expected from chlorination of amino acids, proteins, peptides, and many other natural organic matters present in drinking water.
Mehrsheikh
Akbar
A
Environmental Sciences Technology Center, Monsanto Company, 800 North Lindbergh Blvd. St. Louis, MO 63167, USA. Electronic address: akbar.mehrsheikh@monsanto.com.
Bleeke
Marian
M
Environmental Sciences Technology Center, Monsanto Company, 800 North Lindbergh Blvd. St. Louis, MO 63167, USA.
Brosillon
Stephan
S
Laboratoire Rennais de Chimie et d'Ingénierie des Procédés, Institut de Chimie de Rennes, Ecole Nationale Supérieure de Chimie, avenue du Général Leclerc, 35700 Rennes, France.
Laplanche
Alain
A
Laboratoire Rennais de Chimie et d'Ingénierie des Procédés, Institut de Chimie de Rennes, Ecole Nationale Supérieure de Chimie, avenue du Général Leclerc, 35700 Rennes, France.
Roche
Pascal
P
Véolia Water, Anjou Recherche, Chemin de la digue BP 76 , 78603 Maisons-Lafitte Cedex, France.
D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D002713:Chlorine / Q000737:chemistry* / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000378:metabolism; D009587:Nitrogen Isotopes; D014867:Water; D018508:Water Purification / Q000379:methods; D000097797:Glyphosate
D002245:Carbon Dioxide; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D002713:Chlorine; D005998:Glycine; D008697:Methane; D009587:Nitrogen Isotopes; D014867:Water; D000097797:Glyphosate