Octadecyltrimethoxysilane

Octadecyltrimethoxysilane (OTMS) is an organosilicon compound. This colorless 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.

Octadecyltrimethoxysilane

Names
Preferred IUPAC name Octadecyltrimethoxysilane
Systematic IUPAC name Trimethoxy(octadecyl)silane
Other names n-Octadecyltrimethoxysilane Trimethoxyoctadecylsilane
Identifiers
CAS Number	3069-42-9
3D model (JSmol)	Interactive image Interactive image
Abbreviations	OTMS
Beilstein Reference	5791830
ChemSpider	68956
ECHA InfoCard	100.019.400
EC Number	221-339-2
MeSH	n-Octadecyltrimethoxysilane
PubChem CID	76486
CompTox Dashboard (EPA)	DTXSID40883733
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
SMILES CCCCCCCCCCCCCCCCCC[Si](OC)(OC)OC O(C)[Si](OC)(OC)CCCCCCCCCCCCCCCCCC
Properties
Chemical formula	C21H46O3Si
Molar mass	374.681 g·mol^−1
Appearance	Colorless liquid
Density	0.883 g cm^−3
Melting point	16 to 17 °C (61 to 63 °F; 289 to 290 K)
Boiling point	170 °C (338 °F; 443 K)
Refractive index (nD)	1.438-1.44
Hazards
Safety data sheet
EU classification (DSD) (outdated)	Xi
R-phrases (outdated)	R36, R37, R38
S-phrases (outdated)	S26, S36
NFPA 704 (fire diamond)	1 2 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

References

1. P. Fontaine; F. Rondelez (1995). J. Daillant; P. Guenoun; C. Marques; P. Muller; J. Tran Thanh Van (eds.). Kinetics of Polymerisation in Langmuir Monolayers of n-Alkyltrimethoxysilane. Short and Long Chains at Interfaces.

Further reading

• Hild, R; David, C; Müller, H. U; Völkel, B; Kayser, D. R; Grunze, M (1998). "Formation and Characterization of Self-assembled Monolayers of Octadecyltrimethoxysilane on Chromium: Application in Low-Energy Electron Lithography". Langmuir. 14 (2): 342–346. doi:10.1021/la970438l.
• Vidon, S; Leblanc, R. M (1998). "Langmuir Study of Octadecyltrimethoxysilane Behavior at the Air−Water Interface". The Journal of Physical Chemistry B. 102 (7): 1279–1286. doi:10.1021/jp973334s.