Editing Silicon tetrachloride

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464390493
| ImageFileL1 = Silicon tetrachloride.svg
| ImageFileR1 = Silicon-tetrachloride-3D-vdW.png
| ImageFile2 = Silicon tetrachloride.png
| ImageSize2 = 150px
| ImageClassL1   = skin-invert
| IUPACName = Tetrachlorosilane
| OtherNames = Silicon tetrachloride <br> Tetrachlorosilane
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 23201
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Cl4Si/c1-5(2,3)4
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = FDNAPBUWERUEDA-UHFFFAOYSA-N
| CASNo = 10026-04-7
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 96L75U0BM3
| EINECS = 233-054-0
| PubChem = 24816
| SMILES = [Si](Cl)(Cl)(Cl)Cl
| InChI = 1/Cl4Si/c1-5(2,3)4
| RTECS = VW0525000
| UNNumber = 1818
  }}
|Section2={{Chembox Properties
| Formula = SiCl<sub>4</sub>
| MolarMass = {{val|169.90|u=g/mol}}
| Appearance = Colourless liquid
| Density = 1.483 g/cm<sup>3</sup>
| MeltingPtC = -68.74
| BoilingPtC = 57.65
| Solubility = Reacts to form [[silica]]
| SolubleOther = soluble in [[benzene]], [[toluene]], [[chloroform]], [[diethyl ether|ether]]<ref name=Brauer>{{cite book|author=P. W. Schenk|chapter=Phosphorus(V) fluoride|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=282–683}}</ref>
| VaporPressure = {{val|25.9|ul=kPa}} at {{val|20|u=°C}}
| MagSus = &minus;88.3·10<sup>−6</sup> cm<sup>3</sup>/mol
  }}
|Section3={{Chembox Structure
| CrystalStruct = [[Tetrahedron|Tetrahedral]]
| Coordination = 4
| MolShape = 
  }}
|Section4={{Chembox Thermochemistry
| DeltaHf = −687&nbsp;kJ·mol<sup>−1</sup><ref name=b1>{{cite book| author = Zumdahl, S. S. | title = Chemical Principles | edition = 6th | publisher = Houghton Mifflin | year = 2009 | isbn = 978-0-618-94690-7 | page = A22 }}</ref>
| Entropy = 240&nbsp;J·mol<sup>−1</sup>·K<sup>−1</sup><ref name=b1/>
 }}
|Section7={{Chembox Hazards
| ExternalSDS = [https://www.inchem.org/documents/icsc/icsc/eics0574.htm ICSC 0574 MSDS]
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|315|319|335}}
| PPhrases = {{P-phrases|261|264|271|280|302+352|304+340|305+351+338|312|321|332+313|337+313|362|403+233|405|501}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = W
<!-- |   FlashPt = {{val|-18|u=°C}}  I think that it is an evident mistake. --Incnis Mrsi -->
  }}
|Section8={{Chembox Related
| OtherFunction = [[Chlorosilane]]<br/>[[Dichlorosilane]]<br/>[[Trichlorosilane]]
| OtherFunction_label = chlorosilanes
| OtherAnions = [[Silicon tetrafluoride]]<br/>[[Silicon tetrabromide]]<br/>[[Silicon tetraiodide]]
| OtherCations = [[Carbon tetrachloride]]<br/>[[Germanium tetrachloride]]<br/>[[Tin(IV) chloride]]<br/>[[Titanium tetrachloride]]
  }}
}}
'''Silicon tetrachloride''' or '''tetrachlorosilane''' is the [[inorganic compound]] with the [[chemical formula|formula]] SiCl<sub>4</sub>. It is a colorless [[Volatility (chemistry)|volatile]] [[liquid]] that fumes in air. It is used to produce high purity silicon and [[silica]] for commercial applications. It is a part of the [[chlorosilane]] family.

==Preparation==
Silicon tetrachloride is prepared by the chlorination of various silicon compounds such as [[ferrosilicon]], [[silicon carbide]], or mixtures of silicon dioxide and carbon. The ferrosilicon route is most common.<ref name=Ullmann>{{ Ullmann | author = Simmler, W. | title = Silicon Compounds, Inorganic | doi = 10.1002/14356007.a24_001 }}</ref>

In the laboratory, {{chem2|SiCl4}} can be prepared by treating [[silicon]] with [[chlorine]] at {{convert|600|C|F}}:<ref name=Brauer/>
:{{chem2|Si + 2 Cl2 → SiCl4}}

It was first prepared by [[Jöns Jakob Berzelius]] in 1823.<ref>{{cite journal |last1=Berzelius |first1=Jac. |title=Undersökning af flusspatssyran och dess märkvärdigaste föreningar |journal=Kongliga Vetenskapsakademiens Nya Handlingar [New Proceedings of the Royal Academy of Sciences] |date=1824 |series=3rd series |volume=12 |pages=46–98 |url=https://www.biodiversitylibrary.org/item/107454#page/54/mode/1up |trans-title=Examination of hydrofluoric acid and its most significant compounds |language=Swedish}}  From [https://www.biodiversitylibrary.org/item/107454#page/65/mode/1up pp. 57-58]: "''Då silicium upphettas i en ström ab ''chlor'', tänder det sig och brinner, samt om gasen innehöll atm. luft, lemnar det kiseljord i form af ett ullikt skelett.'' […] ''Silicium glödgadt i en ström af ''iod''gas, har icke kunnat fås att dermed förbinda sig.''" (When silicon is heated in a stream of ''chlorine'', it ignites and burns, as well as if the gas contained atmospheric air, it leaves silica in the form of an odd "skeleton".  If the silicon was previously oxidized to some extent, then the siliceous earth also remains.  Silicon burns in chlorine with equal slowness, whether it has lost its flammability in air or not.  The product of the combustion is condensed and forms a liquid, which, when freed from it, should be colorless. This liquid is quite volatile and easy-flowing; it evaporates in the open air, almost instantly, with the emission of a white smoke and with a residue of siliceous earth. It has a pungent smell, somewhat like cyanide; precipitated in water, it quickly floats up, dissolves for the most part, but leaves a little siliceous earth undissolved; if the quantity of water is small, e.g., a drop of each, then the chlorosilicon floats around and the silica becomes undissolved in an exfoliated, semi-transparent state.  This liquid is analogous to the compound of other electronegative substances with chlorine.  Reacts like acid with litmus paper, so that, by its volatility, the paper reddens quite a distance from the point of contact.  It is the second known example of a compound in which silicon is volatile.  At the ordinary temperature of the air, potassium does not act on it; but if it is heated in the gas of chlorosilicon, it ignites and burns, with a residue of silicon-bound potassium.  Silicon heated in a stream of ''iodine'' gas, could not be made to bond with it.)</ref>

[[Brine]] can be contaminated with [[silica]] when the production of chlorine is a byproduct of a metal refining process from metal chloride ore. In rare occurrences, the [[silicon dioxide]] in silica is converted to silicon tetrachloride when the contaminated brine is [[electrolysis|electrolyzed]].<ref name="White Chlorine">{{cite book|last1=White|first1=George Clifford|title=The handbook of chlorination|date=1986|publisher=Van Nostrand Reinhold|location=New York|isbn=0-442-29285-6|pages=33–34|edition=2nd}}</ref>

==Reactions==

===Hydrolysis and related reactions===
Like other chlorosilanes or [[silane]]s, silicon tetrachloride reacts readily with [[water (molecule)|water]]:
:SiCl<sub>4</sub> + 2 H<sub>2</sub>O → SiO<sub>2</sub> + 4 HCl
The reaction can be noticed on exposure of the liquid to air, as SiCl<sub>4</sub> vapour produces fumes as it reacts with moisture to give a cloud-like aerosol of silica and [[hydrochloric acid]].<ref>{{cite book | title = Advanced Chemistry | last1 = Clugston | first1 =  M. | last2 = Flemming | first2 = R. | year = 2000 | publisher = Oxford University Press | isbn = 978-0199146338 | page = 342 }}</ref> In contrast, [[carbon tetrachloride]] is not readily hydrolyzed.

With [[Alcohol (chemistry)|alcohol]]s it reacts to give orthosilicate [[ester]]s:
:SiCl<sub>4</sub> + 4 ROH → Si(OR)<sub>4</sub> + 4 HCl

===Polysilicon chlorides===
At higher temperatures [[Homologous series|homologues]] of silicon tetrachloride can be prepared by the reaction:
:Si + 2 SiCl<sub>4</sub> → Si<sub>3</sub>Cl<sub>8</sub>
In fact, the chlorination of silicon is accompanied by the formation of [[hexachlorodisilane]] Si<sub>2</sub>Cl<sub>6</sub>. A series of compounds containing up to six silicon atoms in the chain can be separated from the mixture using [[fractional distillation]].<ref name=Brauer/>

===Reactions with other nucleophiles===
Silicon tetrachloride is a classic electrophile in its reactivity.<ref>{{Greenwood&Earnshaw2nd}}</ref> It forms a variety of [[organosilicon compound]]s upon treatment with [[Grignard reagent]]s and [[organolithium compound]]s:
:4 RLi + SiCl<sub>4</sub> → R<sub>4</sub>Si + 4 LiCl
Reduction with hydride reagents affords [[silane]].

==Comparison with other SiX<sub>4</sub> compounds==
{| class="wikitable" style="text-align:center"; border="5" 
!  !! SiH<sub>4</sub> !! SiF<sub>4</sub> !! SiCl<sub>4</sub> !! SiBr<sub>4</sub> !! SiI<sub>4</sub>
|-
| b.p. (˚C)<ref name=collins>''Silicon Compounds, Silicon Halides.'' Collins, W.: Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc, 2001.</ref> || −111.9 || −90.3 || 56.8 || 155.0 || 290.0
|-
| m.p. (˚C)<ref name=collins/> || −185 || −95.0 || −68.8 || 5.0 || 155.0
|-
| Si-X bond length (Å) || >0.74 <ref>{{Cite web|url=https://www.answers.com/Q/What_is_the_bond_length_of_the_H-H_bond|title = What is the bond length of the H-H bond?|website = [[Answers.com]]}}</ref>|| 1.55 || 2.02 || 2.20 || 2.43
|-
| Si-X bond energy (kJ/mol)<ref name=Ebsworth>Ebsworth, E. A. V. In ''Volatile Silicon Compounds;'' Taube, H.; Maddock, A. G.; Inorganic Chemistry; Pergamon Press Book: New York, NY, 1963; Vol. 4.</ref> || 384 || 582 || 391 || 310 || 234
|}

==Uses==
Silicon tetrachloride is used as an intermediate in the manufacture of [[polysilicon]], a hyper-pure form of silicon,<ref name=Ullmann/> since it has a boiling point convenient for purification by repeated [[fractional distillation]]. It is reduced to [[trichlorosilane]] (HSiCl<sub>3</sub>) by hydrogen gas in a hydrogenation reactor, and either directly used in the [[Siemens process]] or further reduced to [[silane]] (SiH<sub>4</sub>) and injected into a [[fluidized bed reactor]]. Silicon tetrachloride reappears in both these two processes as a by-product and is recycled in the hydrogenation reactor. [[Epitaxy#Vapor-phase|Vapor phase epitaxy]] of reducing silicon tetrachloride with hydrogen at approximately 1250&nbsp;°C was done:
: {{chem|SiCl|4}}(g) + 2 {{chem|H|2}}(g) → Si(s) + 4 {{chem|H|Cl|}}(g) at 1250°C<ref name="Morgan&Board">{{cite book|last1=Morgan|first1=D. V.|last2=Board|first2=K.|title=An Introduction To Semiconductor Microtechnology|date=1991|publisher=John Wiley & Sons|location=Chichester, West Sussex, England|isbn=0471924784|page=23|edition=2nd}}</ref>

The produced polysilicon is used as wafers in large amounts by the [[Photovoltaics|photovoltaic]] industry for conventional solar cells made of [[crystalline silicon]] and also by the semiconductor industry.

Silicon tetrachloride can also be hydrolysed to [[fumed silica]]. High purity silicon tetrachloride is used in the manufacture of optical fibres. This grade should be free of hydrogen containing impurities like trichlorosilane. Optical fibres are made using processes like MCVD and OFD where silicon tetrachloride is oxidized to pure silica in the presence of oxygen.

As a feedstock in production of [[Fused quartz|fused silica]].

==Safety and environmental issues==
Pollution from the production of silicon tetrachloride has been reported in China associated with the increased demand for photovoltaic cells that has been stimulated by subsidy programs.<ref>{{cite news | url = https://www.washingtonpost.com/wp-dyn/content/article/2008/03/08/AR2008030802595.html | newspaper = The Washington Post | title = Solar Energy Firms Leave Waste Behind in China | date = 9 March 2008}}</ref>

==See also==
*[[Silicon tetrachloride (data page)]]

==References==
{{Reflist}}
{{Silicon compounds}}
{{Chlorides}}
{{Chlorine compounds}}

{{Authority control}}

[[Category:Chlorides]]
[[Category:Nonmetal halides]]
[[Category:Inorganic silicon compounds]]
[[Category:Chlorosilanes]]