{{distinguish|Tetramethyl orthosilicate}} {{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 470603747 | ImageFile1_Ref = {{chemboximage|correct|??}} | ImageFile1 = Tetraethyl orthosilicate.svg | ImageSize1 = 160px | ImageFile2 = Tetraethyl orthosilicate 3D.png | ImageSize2 = 200px | IUPACName = Tetraethyl orthosilicate | OtherNames = {{ubl|Tetraethoxysilane|Ethyl silicate, tetra-|Silicic acid tetraethyl ester|Silicon(IV) ethoxide|TEOS|Tetraethyl silicate (ortho-)}} |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 6270 | InChI = 1/C8H20O4Si/c1-5-9-13(10-6-2,11-7-3)12-8-4/h5-8H2,1-4H3 | InChIKey = BOTDANWDWHJENH-UHFFFAOYAS | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C8H20O4Si/c1-5-9-13(10-6-2,11-7-3)12-8-4/h5-8H2,1-4H3 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = BOTDANWDWHJENH-UHFFFAOYSA-N | CASNo = 78-10-4 | CASNo_Ref = {{cascite|correct|CAS}} | PubChem = 6517 | UNII_Ref = {{fdacite|changed|FDA}} | UNII = 42064KRE49 | SMILES = CCO[Si](OCC)(OCC)OCC }} |Section2={{Chembox Properties | Formula = {{chem2|Si(OCH2CH3)4}} | Si=1|C=8|H=20|O=4 | Appearance = Colourless liquid | Odor = Sharp, alcohol-like<ref name=PGCH/> | Density = 0.933{{nbsp}}g/mL at 20 °C | MeltingPtC = −77 | BoilingPtC = 168 to 169 | Solubility = Reacts with water, soluble in ethanol, and 2-propanol | VaporPressure = 1{{nbsp}}mmHg<ref name=PGCH/> }} |Section3={{Chembox Hazards | MainHazards = Flammable, harmful by inhalation | FlashPtC = 45 | AutoignitionPtC = | PEL = TWA 100{{nbsp}}ppm (850{{nbsp}}mg/m<sup>3</sup>)<ref name=PGCH>{{PGCH|0282}}</ref> | REL = TWA 10{{nbsp}}ppm (85{{nbsp}}mg/m<sup>3</sup>)<ref name=PGCH/> | IDLH = 700{{nbsp}}ppm<ref name=PGCH/> | LCLo = {{ubl | 1000{{nbsp}}ppm (rat, 4{{nbsp}}hr) | 700{{nbsp}}ppm (guinea pig, 6{{nbsp}}hr) | 1740{{nbsp}}ppm (guinea pig, 15{{nbsp}}min) | 1170 ppm (guinea pig, 2 hr)<ref name=IDLH>{{IDLH|78104|Ethyl silicate}}</ref> }} | LD50 = 6270{{nbsp}}mg/kg (rat, oral)<ref name=IDLH/> }} | Section8={{Chembox Related | OtherCompounds = Tetramethyl orthosilicate }} }}
'''Tetraethyl orthosilicate''', formally named '''tetraethoxysilane''' ('''TEOS''') or '''ethyl silicate''' is an organic compound with the formula {{chem2|Si(OCH2CH3)4}}. TEOS is a colorless liquid. It degrades in water. TEOS is the ethyl ester of orthosilicic acid, {{chem2|Si(OH)4}}. It is the most prevalent alkoxide of silicon.
TEOS is a tetrahedral molecule at Si atom. Like its many analogues, it is prepared by alcoholysis of silicon tetrachloride: :{{chem2|SiCl4 + 4 CH3CH2OH → Si(OCH2CH3)4 + 4 HCl}}
==Applications== TEOS is mainly used as a crosslinking agent in silicone polymers and as a precursor to silicon dioxide in the semiconductor industry.<ref>{{cite journal|doi=10.1016/S0040-6090(98)01117-1|title=Deposition of thick TEOS PECVD silicon oxide layers for integrated optical waveguide applications|journal=Thin Solid Films|volume=334|pages=60–64|year=1998|last1=Bulla|first1=D.A.P|last2=Morimoto|first2=N.I|issue=1–2|bibcode = 1998TSF...334...60B }}</ref>
TEOS is also used as the silica source for synthesis of some zeolites.<ref>Kulprathipanja, Santi (2010) ''Zeolites in Industrial Separation and Catalysis'', Wiley-VCH Verlag GmbH & Co. KGaA, {{ISBN|3527629572}}.</ref> Other applications include coatings for carpets and other objects. TEOS is used in the production of aerogel. These applications exploit the reactivity of the Si-OR bonds.<ref>Rösch, Lutz; John, Peter and Reitmeier, Rudolf "Silicon Compounds, Organic" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim, 2002. {{doi|10.1002/14356007.a24_021}}.</ref> TEOS has historically been used as an additive to alcohol based rocket fuels to decrease the heat flux to the chamber wall of regeneratively cooled engines by over 50%.<ref>{{Cite book|title=Ignition! An Informal History of Liquid Rocket Propellants|last=Clark|first=John D.|publisher=Rutgers University Press|year=1972|isbn=9780813507255|pages=105–106}}</ref>
TEOS is used in steel casting industry as an inorganic binder and stiffener for making silica-based ceramic molding forms (see also sodium silicate).<ref name=":0">{{Cite web |date=June 16, 2022 |title=Связующее Этилсиликат-40, каталог |trans-title=Ethylsilicate 40 binder |url=https://www.himprom.com/products/svyazuyushchee-etilsilikat-40-gost/ |access-date=2022-06-16 |website=www.himprom.com |publisher=ПАО Химпром}}</ref><ref name=":1">{{Cite web |date=June 16, 2022 |title=Связующее Этилсиликат-32, каталог |trans-title=Ethylsilicate 32 binder |url=https://www.himprom.com/products/svyazuyushchee-etilsilikat-32/ |access-date=2022-06-16 |website=www.himprom.com |publisher=ПАО Химпром}}</ref>{{Better source needed|reason=The current source is insufficiently reliable (WP:NOTRS).|date=June 2022}} and as an inorganic binder for coatings (passivation) of different materials such as steel, glass, brass, and wood in order to make surfaces resistant to water, oxygen and high temperatures.<ref name=":0" /><ref name=":1" />{{Better source needed|reason=The current source is insufficiently reliable (WP:NOTRS).|date=June 2022}}. Further applications of TEOS include its use as an additive to solid polymers to enhance their adhesion to glass, steel or wood,<ref name=":0" /><ref name=":1" />{{Better source needed|reason=The current source is insufficiently reliable (WP:NOTRS).|date=June 2022}} as a binder for porcelain teeth crowns,<ref name=":2">{{Cite web |date=June 16, 2022 |title=Тетраэтоксисилан, каталог |trans-title=Tetraethoxysilane, catalogue |url=https://www.himprom.com/products/tetraetoksisilan/ |access-date=2022-06-16 |website=www.himprom.com |publisher=ПАО Химпром}}</ref>{{Better source needed|reason=The current source is insufficiently reliable (WP:NOTRS).|date=June 2022}} and as a precursor to siloxanes.<ref name=":2" />{{Better source needed|reason=The current source is insufficiently reliable (WP:NOTRS).|date=June 2022}}
==Other reactions== TEOS easily converts to silicon dioxide upon the addition of water: :{{chem2|Si(OCH2CH3)4 + 2 H2O → SiO2 + 4 CH3CH2OH}} An idealized equation is shown, in reality the silica produced is hydrated. This hydrolysis reaction is an example of a sol-gel process. The side product is ethanol. The reaction proceeds via a series of condensation reactions that convert the TEOS molecule into a mineral-like solid via the formation of Si-O-Si linkages. Rates of this conversion are sensitive to the presence of acids and bases, both of which serve as catalysts. The Stöber process allows the formation of monodisperse and mesoporous silica.<ref>{{cite book|chapter = Functionalization of Silica Nanoparticles for Corrosion Prevention of Underlying Metal|first1 = Dylan J.|last1 = Boday|first2 = Jason T.|last2 = Wertz|first3 = Joseph P.|last3 = Kuczynski|pages = 121–140|title = Nanomaterials, Polymers and Devices: Materials Functionalization and Device Fabrication|editor-first = Eric S. W.|editor-last = Kong|publisher = John Wiley & Sons|year = 2015|isbn = 9781118866955|chapter-url = https://books.google.com/books?id=djhPCAAAQBAJ&dq=St%C3%B6ber+process&pg=PA131}}</ref><ref>{{cite book|chapter = Nanoparticles and Composites|first = Guido|last = Kicklebick|pages = 227–244|title = The Sol-Gel Handbook: Synthesis, Characterization and Applications|volume = 3|editor1-first = David|editor1-last = Levy|editor2-first = Marcos|editor2-last = Zayat|publisher = John Wiley & Sons|year = 2015|isbn = 9783527334865|chapter-url = https://books.google.com/books?id=9ZSbCgAAQBAJ&dq=St%C3%B6ber+process&pg=PA229}}</ref><ref name = Berg>{{cite book|title = An Introduction to Interfaces and Colloids: The Bridge to Nanoscience|first = John C.|last = Berg|publisher = World Scientific Publishing|year = 2009|isbn = 9789813100985|pages = 367–368, 452–454|chapter-url = https://books.google.com/books?id=nmZIDQAAQBAJ&dq=St%C3%B6ber+process&pg=PA367|chapter = Colloidal Systems: Phenomenology and Characterization}}</ref>
At elevated temperatures (>600 °C), TEOS converts to silicon dioxide: :{{chem2|Si(OCH2CH3)4 → SiO2 + 2 (CH3CH2)2O}} The volatile coproduct is diethyl ether.
==Safety== Inhalation of TEOS induces eye and nose irritation, and eye contact with the liquid is irritating. High exposure to TEOS can lead to pulmonary edema, but hazards can be reduced by atmospheric humidity and vapor pressure conditions.<ref>{{Cite web |last=PubChem |title=Ethyl silicate |url=https://pubchem.ncbi.nlm.nih.gov/source/hsdb/534 |access-date=2024-05-15 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> The mechanism of irritation is similar to that of tetramethyl orthosilicate.
== References == <references/>
==External links== *[http://webbook.nist.gov/cgi/cbook.cgi?ID=C78104 NIST Standard Reference Database 69, June 2005 Release: NIST Chemistry WebBook] *[https://www.cdc.gov/niosh/npg/npgd0282.html CDC – NIOSH Pocket Guide to Chemical Hazards]
Category:Ethoxy compounds Category:Silicate esters