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Chemistry LibreTexts

Diisopropylamide Ion

[ "article:topic", "authorname:ggunawardena" ]
  • Page ID
    39873
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    Diisopropylamide ion (1), usually prepared as the lithium salt (2), is a strong base but, due to steric hindrance at the electron-rich nitrogen atom caused by the bulky isopropyl groups, a very weak nucleophile.

     

     

    Diisopropylamide ion is commonly used to convert enolizable aldehydes and enolizable ketones to corresponding enolate ions, for all practical purposes, quantitatively.

    eg:

     

     

    Notice that K at room temperature is very large.

     

     

    In the reaction, two reactant molecules react to give two product molecules,  Hence, ΔSº ≈ 0; ΔGº ≈ ΔH°.

    Since ΔG° < 1, ΔH° <1; the reaction is exothermic.  Consequently, according to Le Catelier’s principle, the lower the temperature, the higher the equilibrium constant of the reaction.

     

    K at –78°C > 10²³

     

    The reaction, for all practical purposes, is irreversible at –78°C, meaning that diisopropylamide converts 1 to enolate 2 completely.

     

     

    see also directed aldol reaction