Abbreviations NaHMDS Formula C6H18NNaSi2 Appearance off-white solid | Molar mass 183.37 g/mol Density 900 kg/m³ | |
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Sodium bis(trimethylsilyl)amide is the organosilicon compound with the formula ((CH3)3Si)2NNa. This species, usually called NaHMDS (sodium hexamethyldisilazide), is a strong base used for deprotonation reactions or base-catalyzed reactions. Its advantages are that it is commercially available as a solid and it is soluble not only in ethers, such as THF or diethyl ether, but also in aromatic solvents, like benzene and toluene by virtue of the lipophilic TMS groups.
Contents
NaHMDS is quickly destroyed by water to form sodium hydroxide and bis(trimethylsilyl)amine.
Structure
Although the N-Na bond is polar covalent as a solid, when dissolved in nonpolar solvents this compound is trimeric, consisting of a central Na3N3 ring.
Applications in synthesis
NaHMDS is used as a base in organic synthesis. Typical reactions:
NaHMDS is also used as a base to deprotonate other compounds containing weakly acidic O-H, S-H, and N-H bonds. These include cyanohydrins and thiols.
NaHMDS is reagent to convert alkyl halides to amines in a two step process that begins with N-alkylation followed by hydrolysis of the N-Si bonds.
((CH3)3Si)2NNa + RBr → ((CH3)3Si)2NR + NaBr ((CH3)3Si)2NR + H2O → ((CH3)3Si)2O + RNH2This method has been extended to aminomethylation via the reagent (CH3)3Si)2NCH2OMe, which contains a displaceable methoxy group.