Advanced search
Start date
Betweenand

Glyphosate protonation and metal coordination sites

Grant number: 19/12808-9
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): July 01, 2019
Effective date (End): April 30, 2020
Field of knowledge:Physical Sciences and Mathematics - Chemistry
Principal Investigator:Thiago Carita Correra
Grantee:Guilherme Obeid
Home Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:14/15962-5 - Reaction mechanism of asymmetric catalysts by mass spectrometry and gas-phase vibrational ion spectroscopy, AP.JP

Abstract

Glyphosate is an agricultural pesticide used in large scale worldwide, associated mainly to the cultivation of transgenic soybeans. This herbicide is suspected of being associated with cancer cases and other diseases, which promoted a great movement for its banishment, mainly in Europe. However, due to national regulations, Brazil continues to be a great user of this defensive and some studies suggest that its use should even increase in our country because of the decreased demand from other markets. Although not yet clearly elucidated, the relationship of this species with organisms depends, among other factors, on its bioavailability and its dispersion in the environment. For this reason, fundamental glyphosate studies are needed. Given the nature of this compound, composed by diverse functional groups, it is important to precisely determine glyphosate order of protonation and deprotonation, as well as the interaction with metallic ions present in the environment, like Ca2+, for instance. To that end, a number of spectrometric techniques were used, including the 1H nuclear magnetic resonance (NMR) and X-ray structural studies of glyphosate salts and metal cations. The results obtained by these techniques, however, are under discussion, as is the case of the order of protonation determined by 1H NMR, or are considered complementary, as the case of X-ray diffraction, by carrying out measurements in experimental conditions very distant from the environmental conditions. For this reason, the present project proposes the use of mass spectrometry coupled to the vibrational ion spectroscopy technique, supported by electronic structure calculations, to identify the different isomers formed by the processes of protonation, deprotonation and coordination with glyphosate. Thus, this study intends to obtain a definitive description of the protonation equilibrium of this species in solution and the coordination motifs presented by these species at the molecular level.