Browsing by Author "Anipindi, Nageswara Rao."

Now showing 1 - 3 of 3
  • No Thumbnail Available
    PublicationMetadata only
    Base hydrolysis of tris(3-(2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II) in aqueous, SDS and CTAB media: kinetic and mechanistic study
    (Transition Metal Chemistry, 2017-09-08) Bellam, Rajesh.; Anipindi, Nageswara Rao.; Jaganyi, Deogratius.
    The kinetics and mechanism of base hydrolysis of tris(3-(2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II), have been studied in aqueous, sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB) media at 25, 35 and 45 °C under pseudo-first-order conditions, i.e. ≫ . The reaction is first order each in and hydroxide ion. The rate increases with increasing ionic strength in aqueous and SDS media, whereas this parameter has little effect in CTAB. In SDS medium, the rate-determining step involves the reaction between and , whereas in CTAB medium, it involves reaction between a neutral ion pair, {·4CTA+} and ions. The specific rate constants and thermodynamic parameters (E a, ΔH #, ΔS # and ΔG #35°C ) have been evaluated in all three media. The near equal values of ΔG #35°C obtained in aqueous and SDS media suggest that these reactions occur essentially by the same mechanism. Slightly lower ΔG #35°C values in CTAB medium can be attributed to a higher concentration of reactants in the Stern layer. The reaction is inhibited in SDS medium but catalysed in CTAB. The former can be attributed to the anionic surfactant creating more repellent space between the reactants. Catalysis in CTAB medium is ascribed to electrophilic and hydrophilic interactions between hydroxide ion/substrate with the cationic Stern layer, resulting in increased local concentrations of both reactants.
  • No Thumbnail Available
    PublicationMetadata only
    Effect of CTAB and SDS on base hydrolysis of iron(II)-sulphonated and unsulphonated phenyl-1,2,4-triazine complexes - A kinetic and mechanistic study
    (Journal of Molecular Liquids, 2018-05-15) Bellam, Rajesh.; Anipindi, Nageswara Rao.; Jaganyi, Deogratius.
    The effect of cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) on base hydrolysis of iron(II)-triazine complexes viz., tris((3-(4-phenyl)-2-pyridyl)-5,6-bis(4-phenyl)-1,2,4-triazine)iron(II), Fe(PPDT)32+ and its sulphonated analogue, tris(3-(4-(4-phenylsulphonic acid)-2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II), Fe(PPDTS)37‐ has been studied under pseudo-first order conditions at 25, 35, 45 and 55 °C. These reactions are first order with respect to the substrate and hydroxide ion. The rate of base hydrolysis of Fe(PPDT)32+ decreases with the increase in ionic strength in both aqueous and CTAB media whereas the effect is minimal in SDS medium. In the case of Fe(PPDTS)37‐, the opposite is seen i.e., the rate of hydrolysis increases with the increase in ionic strength in both the aqueous and SDS media whereas in CTAB medium it has little effect. Specific rate constants (k2) and activation parameters, Ea, ΔH#, ΔS# and ΔG# have also been evaluated. The results obtained suggest that these reactions occur essentially by the same mechanism in aqueous and micellar media. About 104 times catalysis and 5 times inhibition were noticed in CTAB and SDS media respectively when compared to aqueous medium. The observed catalysis is ascribed to electrostatic and hydrophobic interactions between hydroxide and CTAB ions, whereas the inhibition is attributed to the electrostatic repulsions between hydroxide ion and dodecyl sulphonate anions. Density functional theory (DFT) calculations were found to support the experimental results.
  • No Thumbnail Available
    PublicationMetadata only
    Effect of CTAB and SDS on base hydrolysis of iron(II)-sulphonated and unsulphonated phenyl-1,2,4-triazine complexes - A kinetic and mechanistic study
    (Journal of Molecular Liquids, 2018-05-15) Bellam, Rajesh.; Anipindi, Nageswara Rao.; Jaganyi, Deogratius.
    The effect of cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) on base hydrolysis of iron(II)-triazine complexes viz., tris((3-(4-phenyl)-2-pyridyl)-5,6-bis(4-phenyl)-1,2,4-triazine)iron(II), Fe(PPDT)32+ and its sulphonated analogue, tris(3-(4-(4-phenylsulphonic acid)-2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II), Fe(PPDTS)37‐ has been studied under pseudo-first order conditions at 25, 35, 45 and 55 °C. These reactions are first order with respect to the substrate and hydroxide ion. The rate of base hydrolysis of Fe(PPDT)32+ decreases with the increase in ionic strength in both aqueous and CTAB media whereas the effect is minimal in SDS medium. In the case of Fe(PPDTS)37‐, the opposite is seen i.e., the rate of hydrolysis increases with the increase in ionic strength in both the aqueous and SDS media whereas in CTAB medium it has little effect. Specific rate constants (k2) and activation parameters, Ea, ΔH#, ΔS# and ΔG# have also been evaluated. The results obtained suggest that these reactions occur essentially by the same mechanism in aqueous and micellar media. About 104 times catalysis and 5 times inhibition were noticed in CTAB and SDS media respectively when compared to aqueous medium. The observed catalysis is ascribed to electrostatic and hydrophobic interactions between hydroxide and CTAB ions, whereas the inhibition is attributed to the electrostatic repulsions between hydroxide ion and dodecyl sulphonate anions. Density functional theory (DFT) calculations were found to support the experimental results.