• Kinetics and mechanism of anation of (α, β)S-(hydroxo) (tetraethylenepentamine)cobalt (III) by sulphite in basic medium, the role of anionic micelles

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      https://www.ias.ac.in/article/fulltext/jcsc/107/05/0533-0540

    • Keywords

       

      Anation; sulphito complex; (hydroxo) (tetren) cobalt(III)

    • Abstract

       

      The anation of (α, β)S-(tetren)CoOH2+ by SO32− in alkaline medium (pH>12) produced the S-bonded sulphito complex exclusively. The reaction is reversible andkobs=(k1+k2[OH])[SO32−]T+k−1[OH] is obeyed at [SO32−]=0.005–0.006, [OH]T=0.02−0.30 mol dm−3 (30–45°C,I=1.0 mol dm−3). At 35°C,k1=(3.6±0.6)×10−3 dm3 mol−1 s−1,ΔH=55±10 kJ mol−1,ΔS=−112±34 JK−1 mol−1,k2=(4.3±0.6)×10−2dm6 mol−2 s−1,ΔH=44±11 kJ mol−1,ΔS=−130±36 JK−1 mol−1. The unusually high rate of sulphite substitution particularly in the OH independent path is attributed to the involvement of a reactive internal conjugate base due to the coordinated OH assisted NH-deprotonation of the tetren moiety (Co(tetren)OH2+⇋Co(tetren-H)OH22+). Substantially low values of the activation parameters (ΔH andΔS) particularly the activation entropy is consistent with associative interchange mechanism (Ia) which is further supported by the rate retardation by anionic micelles of SDS. For the pseudo-phase ion-exchange equilibrium (tetren) in the reaction CoOHW2++2NaM+⇋(tetren)CoOHM2++2NaW+, the calculated value ofKex is 219±60 at 35°C.

    • Author Affiliations

       

      A C Dash1 A N Acharya2 A K Patanaik1

      1. Department of Chemistry, Utkal University, Bhubaneswar - 751 004, India
      2. Institute of Textile Technology, Choudwar, Cuttack - 754 025, India
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  • Journal of Chemical Sciences | News

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