“Trimethylsilanol”的意思、由来-开放百科全书

TMS is a contaminant in the atmospheres of spacecraft, where it arises from the degradation of silicone-based materials.^[5] Specifically, it is the volatile product from the hydrolysis of polydimethylsiloxane, which are generally terminated with trimethylsilyl groups:

TMS and related volatile siloxanes are formed by hydrolysis of silicones-based containing materials, which are found in detergents and cosmetic products.

Traces of Trimethylsilanol, together with other volatile siloxanes, are present in biogas and landfill gas, again resulting from the degradation of silicones. As their combustion forms particles of silicates and microcrystalline quartz, which cause abrasion of combustion engine parts, they pose problems for the use of such gases in combustion engines.^[6]

Production

Trimethylsilanol can not be produced by simple hydrolysis of chlorotrimethylsilane, as this reaction leads to the etherification product hexamethyldisiloxane, because of the by-product hydrochloric acid.^[7]

Trimethylsilanol is accessible by weakly basic hydrolysis, since the dimerization can thus be avoided.^[8] Trimethylsilanol can also be obtained by the basic hydrolysis of hexamethyldisiloxane.^[9]

Use

Like other silanols, trimethylsilanol is being tested for use as an antimicrobial agent.^[10]

TMS is used for hydrophobic coating on silicate surfaces. It reacts with the silanol groups (R³SiOH) of the substrate, resulting in a layer of methyl groups.

Properties

Trimethylsilanol is a volatile organic liquid with a boiling point of 98 °C.^[11] The heat of evaporation is 45.64 kJ·mol⁻¹, the evaporation entropy 123 J·K⁻¹·mol⁻¹.^[2] The vapor pressure function according to Antoine is obtained as log₁₀(P) = A−(B/(T+C)) (P in bar, T in K) with A = 5.44591, B = 1767.766 and C = -44.888 in a temperature range from 291 K to 358 K.^[2] Below the melting point at -4.5 °C,^[12] the compound solidifies in a monoclinic crystal lattice.^[13] Trimethylsilanol is a weak acid with a pK_a value of 11.^[14] The acidity is comparable to that of orthosilicic acid, but much higher than the one of alcohols like tert-butanol (pK_a 19^[14]).

References

1. ^¹{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = The Royal Society of Chemistry | date = 2014 | location = Cambridge | page = 696 | doi = 10.1039/9781849733069-FP001 | isbn = 978-0-85404-182-4}}
2. ^¹²Grubb, W.T.; Osthoff, R.C.: Physical Properties of Organosilicon Compounds. II. Trimethylsilanol and Triethylsilanol in J. Am. Chem. Soc. 75 (1953) 2230–2232; {{DOI|10.1021/ja01105a061}}.
3. ^Paul D. Lickiss: The Synthesis and Structure of Organosilanols, Advances in Inorganic Chemistry 1995, Volume 42, Pages 147–262, {{DOI|10.1016/S0898-8838(08)60053-7}}.
4. ^Vadapalli Chandrasekhar, Ramamoorthy Boomishankar, Selvarajan Nagendran: Recent Developments in the Synthesis and Structure of Organosilanols, Chem. Rev. 2004, volume 104, pp 5847–5910, {{DOI|10.1021/cr0306135}}.
5. ^Trimethylsilanol, Harold L. Kaplan, Martin E. Coleman, John T. James: Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants, Volume 1 (1994).
6. ^http://epics.ecn.purdue.edu/bgi/Documents/Fall%25202009/Removal_of_Siloxanes_.pdf {{dead link|date=July 2015}}
7. ^Didier Astruc: Organometallic Chemistry and Catalysis. Springer Science & Business Media, 2007, {{ISBN|978-3-540-46129-6}}, S. 331 ({{Google books|aVyfo52-nRsC||page=331}}).
8. ^J.A. Cella, J.C. Carpenter: Procedures for the preparation of silanols in J. Organomet. Chem. 480 (1994), 23–23; {{DOI|10.1016/0022-328X(94)87098-5}}
9. ^M. Lovric, I. Cepanec, M. Litvic, A. Bartolincic, V. Vinkovic: Croatia Chem. Acta 80 (2007), 109–115
10. ^{{cite journal| journal=Electronic Journal of Biotechnology |volume= 9 |issue= 2 |year=2006 |title=Silanol – A novel class of antimicrobial agent |author=Yun-mi Kim, Samuel Farrah, Ronald H. Baney |url=http://www.ejbiotechnology.info/content/vol9/issue2/full/4/index.html |doi=10.2225/vol9-issue2-fulltext-4 |pages=176}}
11. ^Stepovik, L. P.; Kazakina, S. V.; Martynova, I. M. in Russian Journal of General Chemistry – English Version 70 (2000) 1371–1377 oder Zhurnal Obshchei Khimii 70 (2000) 1459–1461.
12. ^Batuew et al. in Doklady Akademii Nauk SSSR 95 (1954) 531.
13. ^{{ZNaturforsch |Serie=B |Autor=R. Minkwitz, S. Schneider |Titel=Die Tieftemperaturkristallstruktur von Trimethylsilanol |Jahr=1998 |Startseite=426 |Endseite=429 }}
14. ^¹T. Kagiya, Y. Sumida, T. Tachi: An Infrared Spectroscopic Study of hydrogen Bonding Interaction. Structural Studies of Proton-donating and -accepting Powers in Bull. Chem. Soc. Jpn. 43 (1970), 3716–3722.

Occurrence and Production

Occurrence

Production

Use

Properties

References