Trimethylsilyl cyanide

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Trimethylsilyl cyanide

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Template:Longitem	Template:Unbulleted list
Abbreviations	TMSCN
ChEBI	Template:Unbulleted list
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Template:Longitem	Template:Chem2
Molar mass	Template:Chem molar mass
Density	0.793 g/mL at 20 °C
Melting point	Template:Chembox CalcTemperatures
Boiling point	Template:Chembox CalcTemperatures
Solubility	organic solvents
Template:Longitem	1.392
Template:Longitem	Trimethylsilyl chloride

Trimethylsilyl cyanide is the chemical compound with the formula Template:Chem2. This volatile liquid consists of a cyanide group, that is CN, attached to a trimethylsilyl group. The molecule is used in organic synthesis as the equivalent of hydrogen cyanide. It is prepared by the reaction of lithium cyanide and trimethylsilyl chloride:

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Structure

The molecule exhibits the structure of a nitrile-like compound, having the structural formula Template:Chem2. The compound exists in a rapid equilibrium with a small amount of the isomeric isocyanide Template:Chem2. By contrast, the nearly isostructural tert-butyl nitrile does not readily isomerize to tert-butyl isocyanide. The isocyanide isomer can be stabilized by complexation to metals.

Reactions

Trimethylsilyl cyanide hydrolyzes to give hydrogen cyanide and trimethylsilanol:

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In its principal application, it adds across carbon-oxygen double bonds, for example in an aldehyde, to form a new carbon-carbon bond:

RCH=O + (CH₃)₃SiC≡N → N≡C–CHR–OSi(CH₃)₃

The product is an O-silylated cyanohydrin.

One use of this reagent is to convert pyridine-N-oxides into 2-cyanopyridine. This transformation is best done in dichloromethane solution using dimethylcarbamoyl chloride as the activating electrophile. It is possible to use benzoyl chloride but the yields and regioselectivity of the addition of the cyano group are lower.

Acetone cyanohydrin can be used to reversibly generate the cyanide anion.

(4)

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Safety

Trimethylsilyl cyanide behaves equivalently to hydrogen cyanide, a potent poison. The compound can be disposed of by using a mixture of alkali hydroxide and bleach.