Bis(trimethylsilyl)acetamide

Bis(trimethylsilyl)acetamide (BSA) is an organosilicon compound with the formula MeC(OSiMe₃)NSiMe₃ (Me = CH₃). It is a colorless liquid that is soluble in diverse organic solvents, but reacts rapidly with moisture and solvents containing OH and NH groups. It is used in analytical chemistry to increase the volatility of analytes, e.g., for gas chromatography.^[1] It is also used to introduce the trimethylsilyl protecting group in organic synthesis.^[2] A related reagent is N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA).

Bis(trimethylsilyl)acetamide

Names
Preferred IUPAC name Trimethylsilyl N-(trimethylsilyl)ethanecarboximidate
Other names N,O-Bis(trimethylsilyl)acetamide
Identifiers
CAS Number	10416-59-8 Y
3D model (JSmol)	Interactive image Interactive image
Abbreviations	BSA
Beilstein Reference	1306669
ChemSpider	23581 Y 4523073 (E) Y 10516629 (Z) Y
ECHA InfoCard	100.030.799
EC Number	233-892-7
MeSH	N,O-bis(trimethylsilyl)acetamide
PubChem CID	25248 6913588 (E) 5372922 (Z)
RTECS number	AK3000000
UNII	R14N49I64O Y
UN number	2920
CompTox Dashboard (EPA)	DTXSID5051525
InChI InChI=1S/C8H21NOSi2/c1-8(9-11(2,3)4)10-12(5,6)7/h1-7H3 Key: SIOVKLKJSOKLIF-UHFFFAOYSA-N InChI=1/C8H21NOSi2/c1-8(9-11(2,3)4)10-12(5,6)7/h1-7H3/b9-8+
SMILES CC(=N[Si](C)(C)C)O[Si](C)(C)C CC(O[Si](C)(C)C)=N[Si](C)(C)C
Properties
Chemical formula	C8H21NOSi2
Molar mass	203.432 g·mol−1
Appearance	Liquid
Density	0.832 g cm−3
Melting point	24 °C (75 °F; 297 K)
Boiling point	71 to 73 °C (160 to 163 °F; 344 to 346 K) at 35mmHg
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H226, H302, H314
Precautionary statements	P210, P233, P240, P241, P242, P243, P260, P264, P270, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P330, P363, P370+P378, P403+P235, P405, P501
Related compounds
Related Amides	Dimethylacetamide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis and reactions

BSA is prepared by treating acetamide with trimethylsilyl chloride in the presence of a base (Me = CH₃, Et = C₂H₅):^[2]

MeC(O)NH₂ + 2 SiMe₃Cl + 2 Et₃N→ MeC(OSiMe₃)NSiMe₃ + 2 Et₃NHCl

The reaction of BSA with alcohols gives the corresponding trimethylsilyl ether, together with acetamide as a byproduct (Me = CH₃):^[3]

2 ROH + MeC(OSiMe₃)NSiMe₃ → MeC(O)NH₂ + 2 ROSiMe₃

References

1. Blau, Karl; J. M. Halket (1993). Handbook of Derivatives for Chromatography (2nd ed.). John Wiley & Sons. ISBN 0-471-92699-X.
2. Harry Heaney, Jian Cui, “N,O-Bis(trimethylsilyl)acetamide” Encyclopedia of Reagents for Organic Synthesis Copyright © 2007 John Wiley & Sons. doi:10.1002/047084289X.rb208.pub2.
3. Young, Steven D.; Buse, Charles T.; Heathcock, Clayton H. (1985). "2-Methyl-2-(Trimethylsiloxy)pentan-3-one". Organic Syntheses. 63: 79. doi:10.15227/orgsyn.063.0079.