To better understand the molecular structures of glyphosate in different solvents, we have studied several possible conformations, and their relative abundances, of glyphosate and its deprotonated forms, in acetone, acetonitrile, DMSO, water, ethanol, carbon tetrachloride, dichloromethane and gas phase. We have also studied NMR and IR spectra of these species in these solvents. We found that the first protonation of glyphosate in water corresponds to the protonation on the amino group, the second protonation in the phosphonate group, the third protonation in the carboxylic group, and that when the molecule has a neutral charge, the most stable form is the zwitterionic specie with the protonated amino group and the phosphonate group.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas