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The Infrared (IR) spectra:Part-IResults and DiscussionIR spectra of all the oxidized (sulfinyl) compounds reveal characteristic γ (S=O) bands dueto stretching vibrations in the regions of 1070-1030 cm -1 . These stretching vibrations areprominent in all spectrums. Additionally, stretching vibrations characteristic of γ (C-S) wereobserved in all the spectrums in the range of 700-600 cm -1 . Besides these, the usual bandsare observed in the IR spectra of all the compounds, characteristic of γ (C-H), around 3030to 2890 cm -1 , as well as bands corresponding to γ (NH) and γ (CONH) between 1680-1575 cm -1(Table-10).The 1 H NMR spectra:The 1 H NMR spectra of oxidized (sulfinyl) derivatives were taken in DMSO-d 6 . Thesecompounds showed characteristic peaks corresponding to the protons of different groupsand functionalities in the molecules. The 2-methylene protons of the sulfinylmethyllinkage appear as a singlet at around 5.5-5.6 ppm, while the same protons were observedin thio derivatives in the range of 4.35 to 4.40 ppm. This downfield shifting of theseprotons is possibly due to attachment of additional electronegative atom (oxygen) to theneighboring sulfur atom. The NH protons present in these compounds at the 3 position ofthe pyrimidine ring and on the benzimidazole ring were observed much downfield, fallingin the range of 12-14 ppm. However, in some of the compounds the NH protons are notseen in the spectra probably due to very faint or broad pecks. All the aromatic protonspresent in the molecules were observed as a multiplet at 7-8 ppm (Table-10).The Mass spectra:The fragmentation pattern of the condensed sulfinyl derivatives under electron impact hasbeen studied. Though, the electron impact is a standard procedure for the ionizations ofmolecules in mass spectroscopy, this technique sometime have disadvantage, when itresults in the disappearance of the molecular ion peak so that the molecular weight of theanalyte cannot be established. 44 In the mass spectrum of sulfiny derivatives, the molecularion peak was not observed. This is may be due the very labile nature of the oxygen atomattached to the sulfur atom. The fragmentation pattern of these molecules is almost sameas observed for corresponding thio derivatives (Table-10).The common fragmentation pattern is depicted in Scheme-25. This decomposition ofmolecular ion involves loss of SO to give the daughter ion (c). Subsequently, loss of109