Trimethylsilyl cyanide

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Trimethylsilyl cyanide
Trimethylsilyl-cyanide-skeletal.png Trimethylsilyl-cyanide-3D-vdW.png
Abbreviations TMSCN
CAS number 7677-24-9 YesY
PubChem 82115
ChemSpider 74110 YesY
Jmol-3D images Image 1
Molecular formula C4H9NSi
Molar mass 99.21 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 reacts with water
Solubility organic solvents
Refractive index (nD) 1.392
R-phrases R11 R26/27/28 R29
S-phrases S16 S36/37/39 S45
Flash point 1 °C (34 °F; 274 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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]

LiCN + (CH3)3SiCl → (CH3)3SiCN + LiCl

In its principal reaction, it adds across carbon-oxygen double bonds, for example in an aldehyde:

RCHO + (CH3)3SiCN → RCH(CN)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.


Trimethylsilyl cyanide is treated with care since it hydrolyzes to give hydrogen cyanide:

2 (CH3)3SiCN + H2O → (CH3)3SiOSi(CH3)3 + 2 HCN


  1. ^ Livinghouse, T. (1990), "Trimethylsilyl Cyanide: Cyanosilation of p-Benzoquinone", Org. Synth. ; Coll. Vol. 7: 517