Trimethylsilyl cyanide

Trimethylsilyl cyanide is the chemical compound with the formula (CH₃)₃SiCN. 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:^[1][2]

LiCN + (CH₃)₃SiCl → (CH₃)₃SiCN + LiCl

Trimethylsilyl cyanide

Names
Preferred IUPAC name Trimethylsilanecarbonitrile
Other names Cyanotrimethylsilane; TMS cyanide; Trimethylsilylnitrile; Trimethylsilylcarbonitrile; Trimethylsilylformonitrile
Identifiers
CAS Number	7677-24-9 Y
3D model (JSmol)	Interactive image
Abbreviations	TMSCN
ChemSpider	74110 Y
ECHA InfoCard	100.028.780
EC Number	231-657-3
PubChem CID	82115
CompTox Dashboard (EPA)	DTXSID9064766
InChI InChI=1S/C4H9NSi/c1-6(2,3)4-5/h1-3H3 Y Key: LEIMLDGFXIOXMT-UHFFFAOYSA-N Y InChI=1/C4H9NSi/c1-6(2,3)4-5/h1-3H3 Key: LEIMLDGFXIOXMT-UHFFFAOYAM
SMILES C[Si](C)(C)C#N
Properties
Chemical formula	(CH3)3SiCN
Molar mass	99.208 g·mol−1
Density	0.793 g/mL at 20 °C
Melting point	8 to 11 °C (46 to 52 °F; 281 to 284 K)
Boiling point	114 to 117 °C (237 to 243 °F; 387 to 390 K)
Solubility in water	hydrolyzes
Solubility	organic solvents
Refractive index (nD)	1.392
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Poisonous like hydrogen cyanide
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H300, H310, H330, H410
Precautionary statements	P210, P233, P240, P241, P242, P243, P260, P262, P264, P270, P271, P273, P280, P284, P301+P310, P302+P350, P303+P361+P353, P304+P340, P310, P320, P321, P322, P330, P361, P363, P370+P378, P391, P403+P233, P403+P235, P405, P501
Flash point	1 °C (34 °F; 274 K)
Related compounds
Other anions	Trimethylsilyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Structure

The molecule exhibits the structure of a nitrile-like compound, having the structural formula (CH₃)₃Si−C≡N. The compound exists in a rapid equilibrium with a small amount of the isomeric isocyanide (CH₃)₃Si−N⁺≡C⁻.^[3] 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.^[4]

Reactions

Trimethylsilyl cyanide hydrolyzes to give hydrogen cyanide and trimethylsilanol:

(CH₃)₃Si−CN + H₂O → (CH₃)₃Si−OH + HCN

In its principal application, it adds across carbon-oxygen double bonds, for example in an aldehyde, to form a new carbon-carbon bond:^[2]

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.^[5]

(4)

Safety

Trimethylsilyl cyanide behaves equivalently to hydrogen cyanide, a potent poison.^[2] The compound can be disposed of by using a mixture of alkali hydroxide and bleach.^[6]