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
3D model (JSmol)
Abbreviations TMSCN
ChemSpider
ECHA InfoCard 100.028.780
EC Number
  • 231-657-3
  • InChI=1S/C4H9NSi/c1-6(2,3)4-5/h1-3H3 checkY
    Key: LEIMLDGFXIOXMT-UHFFFAOYSA-N checkY
  • InChI=1/C4H9NSi/c1-6(2,3)4-5/h1-3H3
    Key: LEIMLDGFXIOXMT-UHFFFAOYAM
  • C[Si](C)(C)C#N
Properties
C4H9NSi
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)
hydrolyzes
Solubility organic solvents
1.392
Hazards
GHS labelling:
GHS02: FlammableGHS06: ToxicGHS09: Environmental hazard
Danger
H225, H300, H310, H330, H410
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).
checkY verify (what is checkY☒N ?)
Infobox references

Structure

The molecule exhibits the structure of a nitrile-like compound. The compound exists in a rapid equilibrium with a small amount of the isomeric isocyanide (CH3)3SiNC.[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)3SiCN + H2O → (CH3)3SiOH + 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]

References
  1. Livinghouse, T. (1981). "Trimethylsilyl Cyanide: Cyanosilation of p-Benzoquinone". Organic Syntheses. 60: 126. doi:10.15227/orgsyn.060.0126.
  2. Groutas, William C.; Jin, Zhendong; Zhang, Heng (2011). "Cyanotrimethylsilane". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rc276.pub2. ISBN 978-0471936237.
  3. Booth, M. R.; Frankiss, S. G. (1968). "Trimethylsilyl isocyanide". Chem. Commun. (21): 1347–1348. doi:10.1039/C19680001347.
  4. Bose, Moumita; Moula, Golam; Begum, Ameerunisha; Sarkar, Sabyasachi (2018). "Synthesis and Characterization of Cyano and Isocyano Complexes of Bis(dithiolato) Molybdenum Using Me3SiCN: A Route to a Cyanide-Bridged Multimer to a Monomer". New Journal of Chemistry. 42 (7): 5580–5592. doi:10.1039/C8NJ00246K.
  5. Nazarov, N. ; Zav'yalov, I. J. Gen. Chem. USSR (Engl. Transl.) 1954, 24, 475 [C.A., 49, 6139f (1955)].
  6. MSDS of trimethylsilyl cyanide. (PDF). Gelest. [Jun 13, 2019]
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