Sodium bisamide is the chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the formula ((CH₃)₃Si)₂NNa. This species, usually called NaHMDS (sodium hexamethyldisilazide), is a strong base

Base (chemistry)

For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

 used for deprotonation reactions or base catalyzed reaction. Its advantages are that it is available as a solid and it is soluble in a wide range of nonpolar solvents such as THF

ThF

Follicular B helper T cells , are antigen-experienced CD4+ T cells found in the B cell follicles of secondary lymphoid organs such as lymph nodes, spleens and Peyer's patches, and are identified by their constitutive expression of the B cell follicle homing receptor CXCR5...

, diethyl ether

Diethyl ether

Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

, benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

, and toluene

Toluene

Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...

 by virtue of the lipophilic TMS

Trimethylsilyl

A trimethylsilyl group is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si3], which is in turn bonded to the rest of a molecule...

 groups.

NaHMDS is quickly destroyed by water to form sodium hydroxide and bis(trimethylsilyl)amine

Bis(trimethylsilyl)amine

Bisamine is an organosilicon compound with the molecular formula [3Si]2NH. The molecule is a derivative of ammonia with trimethylsilyl groups in place of two hydrogen atoms...

.

Structure

It is common that polar organometallic reagents are depicted as ions, when in fact such species are rarely ionic. The structure shown in the figure is a better representation - the sodium atom is attached to the nitrogen atom via a polar covalent bond. When unsolvated, this compound is trimeric in the solid state.

Applications in synthesis

NaHMDS is widely used as a base for C-H acids. Typical reactions:

• To deprotonate ketone
  Ketone
  In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
  
  s and ester
  Ester
  Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
  
  s to generate enolate derivatives.
• Generate halocarbenes such as CHBr and CHI by dehydrohalogenation of the CH₂X₂ (X = Br, I). These carbene reagents add to alkenes to give substituted cyclopropane
  Cyclopropane
  Cyclopropane is a cycloalkane molecule with the molecular formula C3H6, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms...
  
  s.
• To generate Wittig
  Wittig
  Wittig is a surname, and may refer to:* Curt Wittig , American chemist* David Wittig , American executive* Edward Wittig , Polish sculptor* Georg Wittig , German chemist...
  
   reagents via deprotonation of phosphonium salt
  Phosphonium salt
  A phosphonium salt is a salt containing the phosphonium ion such as phosphonium iodide . More commonly, phosphonium refers to a quaternary organic derivative such as tetraphenylphosphonium chloride, 4P+ Cl- and tetramethylphosphonium iodide, [P4]+I−.Alkyltriphenylphosphonium salts are widely...
  
  s.
• Deprotonate cyanohydrin
  Cyanohydrin
  A cyanohydrin is a functional group found in organic compounds. Cyanohydrins have the formula R2CCN, where R is H, alkyl, or aryl. Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids...
  
  s.

NaHMDS is also used as a base for N-H acids.

NaHMDS reacts with alkyl halides to give amine derivatives:₃Si)₂NNa + RBr → (CH₃)₃Si)₂NR + NaBr₃Si)₂NR + H₂O → (CH₃)₃Si)₂O + RNH₂
This method has been extended to aminomethylation via the reagent (CH₃)₃Si)₂NCH₂OMe, which contains a displaceable methoxy group.

• To deprotonate precursors to give stable carbenes.