• K Sreekumar

      Articles written in Journal of Chemical Sciences

    • Poly(methyl methacrylate) supported Cr(VI) reagents: Preparation and applications

      Shiney Abraham P K Rajan K Sreekumar

      More Details Abstract Fulltext PDF

      Divinyl benzene (DVB), ethyleneglycoldimethacrylate (EGDMA) and NN′-methylenebis-acrylamide (NN′-MBA) cross-linked poly(methyl methacrylate)(PMMA)-supported pyrazolinium chromate, chlorochromate and pyrazole-CrO3 complex resins, were prepared and used as oxidising reagents for alcohols. These resins selectively oxidise primary alcohols to aldehydes and secondary alcohols to ketones. They possess the desired characteristics of polymeric reagents, including operational simplicity, filterability and regenerability. NN′-MBA crosslinked poly(methyl methacrylate)-supported pyrazolinium Cr(VI) reagents are more efficient in terms of functional group capacity, reaction time and product yield.

    • Polystyrene-supported hydroxamic dithiocarbonic anhydrides: A new class of acyl transfer reagents

      P N Sophiamma K Sreekumar

      More Details Abstract Fulltext PDF

      Polystyrene-supported hydroxamic dithiocarbonic anhydrides were developed as a new class of regenerable solid phase reagents for acylating amino groups selectively. The reagent was prepared from crosslinked polystyrene support by a series of polymer analogous reactions. The crosslinking agents used were divinylbenzene (DVB) and ethyleneglycol dimethacrylate (EGDMA). The reagents were found to transfer their acyl groups to amines in solution at room temperature, yielding a solution of the corresponding amides. The influence of solvent, temperature, molar ratio and duration of reaction were studied to find out the optimum conditions. The spent reagent can be regenerated several times by a simple reaction, without significant loss in activity.

    • Polystyrene supportedt-butyl chromates: Effect of the degree of crosslinking on reactivity

      K Geethakumari K Sreekumar

      More Details Abstract Fulltext PDF

      Polystyrene supportedt-butyl chromate reagents were prepared using divinylbenzene as the crosslinking agent. The extent of crosslinking was varied from 2 to 20% (2, 5, 10, 15 and 20%). These polystyrene systems appeared to be amenable to structural variations for studying the effect of the nature and extent of crosslinking on the reactivity of the attached functional groups. Polystyrene supportedt-butyl chromates, having varying crosslink densities, were used to oxidise alcohols to the carbonyl compounds. Reagents prepared from 2% crosslinked resins gave better results. A regular decrease in the extent of functionalization was noticed as the degree of crosslinking was increased and the capacity of the functional group was found to be minimum for 20% crosslinked resin.

  • Journal of Chemical Sciences | News

© 2021-2022 Indian Academy of Sciences, Bengaluru.