title: Thermodynamic Study on the Protonation Reactions of Glyphosate in Aqueous Solution: Potentiometry, Calorimetry and NMR spectroscopy.
abstract: Glyphosate [N-(phosphonomethyl)glycine] has been described as the ideal herbicide because of its unique properties. There is some conflicting information concerning the structures and conformations involved in the protonation process of glyphosate. Protonation may influence the chemical and physical properties of glyphosate, modifying its structure and the chemical processes in which it is involved. To better understand the species in solution associated with changes in pH, thermodynamic study (potentiometry, calorimetry and NMR spectroscopy) about the protonation pathway of glyphosate is performed. Experimental results confirmed that the order of successive protonation sites of totally deprotonated glyphosate is phosphonate oxygen, amino nitrogen, and finally carboxylate oxygen. This trend is in agreement with the most recent theoretical work in the literature on the subject (J. Phys. Chem. A 2015, 119, 5241-5249). The result is important because it confirms that the protonated site of glyphosate in pH range 7-8, is not on the amino but on the phosphonate group instead. This corrected information can improve the understanding of the glyphosate chemical and biochemical action.
authors: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics , Mianyang, Sichuan 621999, China.
authors: Bijun
authors: B
authors: Liu
authors: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics , Mianyang, Sichuan 621999, China.
authors: Lan
authors: L
authors: Dong
authors: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics , Mianyang, Sichuan 621999, China.
authors: Qianhong
authors: Q
authors: Yu
authors: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics , Mianyang, Sichuan 621999, China.
authors: Xingliang
authors: X
authors: Li
authors: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences , Beijing 100012, China.
authors: Fengchang
authors: F
authors: Wu
authors: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics , Mianyang, Sichuan 621999, China.
authors: Zhaoyi
authors: Z
authors: Tan
authors: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics , Mianyang, Sichuan 621999, China.
authors: Shunzhong
authors: S
authors: Luo
mesh_terms: D002151:Calorimetry / Q000379:methods*; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011199:Potentiometry / Q000379:methods*; D011522:Protons; D012996:Solutions / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D011522:Protons; D012996:Solutions; D014867:Water; D000097797:Glyphosate