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The two-substituted-4,6-di-( alkylamino )-1 ,3,5-triazines ( s-triazines) are well known pesticides molecules that present five potential sites for protonation reaction in the gas phase. The protonation sites in polyfunctional molecules may be directly identified by using Plasma Desportion Mass spectrometry methods (PD-MSl In this work, we present a theoretical analysis to predict protonation sites. Three families of 2-X substituted-s-triazines (X=Cl,SCH3, and OCH3) studied is presented. The influence of the X and alkyl substituents on the fragmentation processes under PD conditions was investigated in detail1•

Predicted proton affinities performed on the neutral and protonated systems at their equilibrium geometries were optimized at MP2/HF/6-31 G** level of theory. Calculations seems to correlate well with the experimental values (when available). Theoretical infrared intensities with molecular orbitals and bonding of these molecules have also been examined.