Diisopropylamide Ion

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

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