Octadecyltrimethoxysilane

Octadecyltrimethoxysilane
Preferred IUPAC name Octadecyltrimethoxysilane
Systematic name Trimethoxy(octadecyl)silane
Other names n-Octadecyltrimethoxysilane Trimethoxyoctadecylsilane
Identifiers
Abbreviations	OTMS
CAS number	3069-42-9 Y
PubChem	76486
ChemSpider	68956 Y
EC number	221-339-2
MeSH	n-Octadecyltrimethoxysilane
Beilstein Reference	5791830
Jmol-3D images	Image 1 Image 2
SMILES CCCCCCCCCCCCCCCCCC[Si](OC)(OC)OC O(C)[Si](OC)(OC)CCCCCCCCCCCCCCCCCC
InChI InChI=1S/C21H46O3Si/c1-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-25(22-2,23-3)24-4/h5-21H2,1-4H3 Key: SLYCYWCVSGPDFR-UHFFFAOYSA-N InChI=1/C21H46O3Si/c1-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-​21-25(22-2,23-3)24-4/h5-21H2,1-4H3
Properties
Molecular formula	C21H46O3Si
Molar mass	374.67 g mol−1
Exact mass	374.321621871 g mol-1
Appearance	Colorless liquid
Density	0.883 g cm-3
Melting point	16-17 °C, 289-290 K, 61-63 °F
Boiling point	170 °C, 443 K, 338 °F
Refractive index (nD)	1.438-1.44
Hazards
MSDS	[1]
EU classification	Xi
R-phrases	R36, R37, R38
S-phrases	S26, S36
NFPA 704	1 2 0
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Octadecyltrimethoxysilane is an organosilicon compound, commonly called OTMS. This colourless liquid is used for preparing hydrophobic coatings and self-assembled monolayers. It is sensitive toward water, irreversibly degrading to a siloxane polymer.^[1] It places a C₁₈H₃₉SiO₃ "cap" on oxide surfaces. The formation of OTMS monolayers is used for converting hydrophilic surfaces to hydrophobic surfaces, e.g. for use in certain areas of nanotechnology and analytical chemistry.

References

1. ^ P. Fontaine and F. Rondelez, Kinetics of Polymerisation in Langmuir Monolayers of n-Alkyltrimethoxysilane, Short and Long Chains at Interfaces, Edited by: J. Daillant, P. Guenoun, C. Marques, P. Muller, J. Tran Thanh Van. 1995.

Further reading (specialized articles)

• R. Hild, C. David, H. U. Müller, B. Völkel, D. R. Kayser, and M. Grunze. Formation and Characterization of Self-assembled Monolayers of Octadecyltrimethoxysilane on Chromium: Application in Low-Energy Electron Lithography", Langmuir, 1998, 14 (2), pp 342–346.
• Vidon, S., Leblanc, Langmuir study of octadecyltrimethoxysilane behavior at the air-water interface, Journal of Physical Chemistry B, 1998.