Abstract Previous kinetic studies on the addition of aliphatic thiols to activated nitriles suggest that the formation of iminothioesters (possible prebiotic precursors of thioesters) occurs through the nucleophilic addition of thiolate to the C=N group of the activated nitrile in its acidic form:$$R S^ {\ominus} + A - CH{_2} - C \equiv N {\overset {{H^ + }} \leftrightarrows} A - CH{_2} - \begin{array}{*{20}c} C \\ | \\ {SR} \\ \end{array} = NH$$ It seemed also that this addition occurs only when the pKA of the thiol is lower than the pKA of the activated nitrile. In order to test this hypothesis, and to generalize this mechanism, similar studies have been carried out using the same nitriles (A=CN; CHO), but with thiols having lower pKA (substituted thiophenols). The results of these studies, using p-aminothiophenol (pKA=6.85), p-chlorothiophenol (pKA=5.90) and p-nitrothiophenol (pKA=4.60), including the determination of rate and equilibrium constants, is presented.


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    Title :

    Prebiotic formation of iminothioesters. II: Addition of thiophenols to malonic nitriles


    Contributors:

    Published in:

    Publication date :

    1984




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English



    Classification :

    Local classification TIB:    535/3908/4290
    BKL:    44.71 Verkehrsmedizin



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