Dimethyldichlorosilane

Last updated
Dimethyldichlorosilane
Dichlorodimethylsilane.svg
Dichlorodimethylsilane-MW-3D-balls.png
Dichlorodimethylsilane-MW-3D-vdW.png
Names
Preferred IUPAC name
Dichlorodi(methyl)silane
Other names
Dichlorodimethylsilane, dichlorodimethylsilicon, dimethylsilicon dichloride, dimethylsilane dichloride, DMDCS
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.000.820 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 200-901-0
PubChem CID
RTECS number
  • VV3150000
UNII
UN number 1162
  • InChI=1S/C2H6Cl2Si/c1-5(2,3)4/h1-2H3 Yes check.svgY
    Key: LIKFHECYJZWXFJ-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C2H6Cl2Si/c1-5(2,3)4/h1-2H3
    Key: LIKFHECYJZWXFJ-UHFFFAOYAT
  • C[Si](C)(Cl)Cl
Properties
C2H6Cl2Si
Molar mass 129.06 g·mol−1
AppearanceClear liquid
Density 1.07 g·cm−3 (l)
Melting point −76 °C (−105 °F; 197 K)
Boiling point 70 °C (158 °F; 343 K)
Decomposes in water
Hazards
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-exclam.svg
Danger
H225, H315, H319, H335
P210, P233, P240, P241, P242, P243, P261, P264, P271, P280, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P370+P378, P403+P233, P403+P235, P405, P501
Flash point −9 °C (16 °F; 264 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si(CH3)2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made on an industrial scale as the principal precursor to dimethylsilicone and polysilane compounds.

Contents

History

The first organosilicon compounds were reported in 1863 by Charles Friedel and James Crafts who synthesized tetraethylsilane from diethylzinc and silicon tetrachloride. [1] However, major progress in organosilicon chemistry did not occur until Frederick Kipping and his students began experimenting with diorganodichlorosilanes (R2SiCl2) that were prepared by reacting silicon tetrachloride with Grignard reagents. Unfortunately, this method suffered from many experimental problems. [2]

In the 1930s, the demand for silicones increased due to the need for better insulators for electric motors and sealing materials for aircraft engines, and with it the need for a more efficient synthesis of dimethyldichlorosilane. To solve the problem, General Electric, Corning Glass Works, and Dow Chemical Company began a partnership that ultimately became the Dow Corning Company. During 1941–1942, Eugene G. Rochow, a chemist from General Electric, and Richard Müller, working independently in Germany, found an alternate synthesis of dimethyldichlorosilane that allowed it to be produced on an industrial scale. [1] This Direct Synthesis, or Direct process, which is used in today’s industry, involves the reaction of elemental silicon with methyl chloride in the presence of a copper catalyst.

Preparation

Rochow's synthesis involved passing methyl chloride through a heated tube packed with ground silicon and copper(I) chloride. [2] The current industrial method places finely ground silicon in a fluidized bed reactor at about 300 °C. The catalyst is applied as Cu2O. Methyl chloride is then passed through the reactor to produce mainly dimethyldichlorosilane.

2 CH3Cl + Si → (CH3)2SiCl2

The mechanism of the direct synthesis is not known. However, the copper catalyst is essential for the reaction to proceed.

In addition to dimethyldichlorosilane, products of this reaction include CH3SiCl3, CH3SiHCl2, and (CH3)3SiCl, which are separated from each other by fractional distillation. The yields and boiling points of these products are shown in the following chart. [3]

ProductYield (%)Boiling pt (°C)
(CH3)2SiCl280–9070.0
CH3SiCl35–1565.7
CH3SiHCl23–540.7
(CH3)3SiCl3–557.3

Main reactions

Dimethyldichlorosilane hydrolyzes to form linear and cyclic silicones, compounds containing Si-O backbones. The length of the resulting polymer is dependent on the concentration of chain ending groups that are added to the reaction mixture. The rate of the reaction is determined by the transfer of reagents across the aqueous-organic phase boundary; therefore, the reaction is most efficient under turbulent conditions. The reaction medium can be varied further to maximize the yield of a specific product.

n(CH3)2SiCl2 + nH2O → [(CH3)2SiO]n + 2nHCl
m(CH3)2SiCl2 + (m+1)H2O → HO[Si(CH3)2O]mH + 2mHCl

Dimethyldichlorosilane reacts with methanol to produce dimethoxydimethylsilanes.

(CH3)2SiCl2 + 2CH3OH → (CH3)2Si(OCH3)2 + 2HCl

Although the hydrolysis of dimethoxydimethylsilanes is slower, it is advantageous when the hydrochloric acid byproduct is unwanted: [3]

n(CH3)2Si(OCH3)2 + nH2O → [(CH3)2SiO]n + 2nCH3OH

Because dimethyldichlorosilane is easily hydrolyzed, it cannot be handled in air. One method used to overcome this problem is to convert it to a less reactive bis(dimethylamino)silane.

(CH3)2SiCl2 + 4HN(CH3)2 → (CH3)2Si[N(CH3)2]2 + 2H2N(CH3)2Cl

Another benefit to changing dimethyldichlorosilane to its bis(dimethylamino)silane counterpart is that it forms an exactly alternating polymer when combined with a disilanol comonomer. [4]

n(CH3)2Si[N(CH3)2]2 + nHO(CH2)2SiRSi(CH2)2OH → [(CH3)2SiO(CH2)2SiRSi(CH2)2O]n + 2nHN(CH3)2

Sodium metal can be used to polymerize dimethyldichlorosilane, producing polysilane chains with a Si-Si backbone. For example, dodecamethylcyclohexasilane can be prepared in this way: [5]

6 (CH3)2SiCl2 + 12 M → ((CH3)2Si)6 + 12 MCl

The reaction also produces polydimethylsilane and decamethylpentasilane. Diverse types of dichlorosilane precursors, such as Ph 2SiCl2, can be added to adjust the properties of the polymer. [3]

In organic synthesis it (together with its close relative diphenyldichlorosilane) is used as a protecting group for gem-diols.

Applications

Container with the substance, showing UN number 1162, in Japan. Container [( 22T0 )] EXFU 175174(7) [( Pictures taken in Japan )] (cropped).jpg
Container with the substance, showing UN number 1162, in Japan.

The main purpose of dimethyldichlorosilane is for use in the synthesis of silicones, an industry that was valued at more than $10 billion per year in 2005. It is also employed in the production of polysilanes, which in turn are precursors to silicon carbide. [3] In practical uses, dichlorodimethylsilane can be used as a coating on glass to avoid the adsorption of micro-particles. [6]

Related Research Articles

Silane is an inorganic compound with chemical formula, SiH4. It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Silane with alkyl groups are effective water repellents for mineral surfaces such as concrete and masonry. Silanes with both organic and inorganic attachments are used as coupling agents.

<span class="mw-page-title-main">Trichlorosilane</span> Chemical compound

Trichlorosilane is an inorganic compound with the formula HCl3Si. It is a colourless, volatile liquid. Purified trichlorosilane is the principal precursor to ultrapure silicon in the semiconductor industry. In water, it rapidly decomposes to produce a siloxane polymer while giving off hydrochloric acid. Because of its reactivity and wide availability, it is frequently used in the synthesis of silicon-containing organic compounds.

Chloromethane, also called methyl chloride, Refrigerant-40, R-40 or HCC 40, is an organic compound with the chemical formula CH3Cl. One of the haloalkanes, it is a colorless, odorless, flammable gas. Methyl chloride is a crucial reagent in industrial chemistry, although it is rarely present in consumer products, and was formerly utilized as a refrigerant.

Silicon tetrachloride or tetrachlorosilane is the inorganic compound with the formula SiCl4. It is a colourless volatile liquid that fumes in air. It is used to produce high purity silicon and silica for commercial applications.

<span class="mw-page-title-main">Titanium tetrachloride</span> Inorganic chemical compound

Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as "tickle" or "tickle 4" due to the phonetic resemblance of its molecular formula to the word.

<span class="mw-page-title-main">Polydimethylsiloxane</span> Chemical compound

Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, as its versatility and properties lead to many applications.

<span class="mw-page-title-main">Silylene</span> Chemical compound

Silylene is a chemical compound with the formula SiH2. It is the silicon analog of methylene, the simplest carbene. Silylene is a stable molecule as a gas but rapidly reacts in a bimolecular manner when condensed. Unlike carbenes, which can exist in the singlet or triplet state, silylene (and all of its derivatives) are singlets.

<span class="mw-page-title-main">Siloxane</span> Si–O–Si chemical bond

A siloxane is a functional group in organosilicon chemistry with the Si−O−Si linkage. The parent siloxanes include the oligomeric and polymeric hydrides with the formulae H(OSiH2)nOH and (OSiH2)n. Siloxanes also include branched compounds, the defining feature of which is that each pair of silicon centres is separated by one oxygen (O2-) atom. The siloxane functional group forms the backbone of silicones, the premier example of which is polydimethylsiloxane (PDMS). The functional group R3SiO− (where the three Rs may be different) is called siloxy. Siloxanes are manmade and have many commercial and industrial applications because of the compounds’ hydrophobicity, low thermal conductivity, and high flexibility.

Chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The parent chlorosilane is silicon tetrachloride.

<span class="mw-page-title-main">Trimethylsilyl chloride</span> Chemical compound

Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound (silyl halide), with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry.

<span class="mw-page-title-main">Organosilicon chemistry</span> Organometallic compound containing carbon–silicon bonds

Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, flammable, hydrophobic, and stable to air. Silicon carbide is an inorganic compound.

Hydrosilanes are tetravalent silicon compounds containing one or more Si-H bond. The parent hydrosilane is silane (SiH4). Commonly, hydrosilane refers to organosilicon derivatives. Examples include phenylsilane (PhSiH3) and triethoxysilane ((C2H5O)3SiH). Polymers and oligomers terminated with hydrosilanes are resins that are used to make useful materials like caulks.

<span class="mw-page-title-main">Thiophosphoryl chloride</span> Chemical compound

Thiophosphoryl chloride is an inorganic compound with the formula PSCl3. It is a colorless pungent smelling liquid that fumes in air. It is synthesized from phosphorus chloride and used to thiophosphorylate organic compounds, such as to produce insecticides.

<span class="mw-page-title-main">Methyltrichlorosilane</span> Chemical compound

Methyltrichlorosilane, also known as trichloromethylsilane, is a monomer and organosilicon compound with the formula CH3SiCl3. It is a colorless liquid with a sharp odor similar to that of hydrochloric acid. As methyltrichlorosilane is a reactive compound, it is mainly used a precursor for forming various cross-linked siloxane polymers.

The direct process, also called the direct synthesis, Rochow process, and Müller-Rochow process is the most common technology for preparing organosilicon compounds on an industrial scale. It was first reported independently by Eugene G. Rochow and Richard Müller in the 1940s.

<span class="mw-page-title-main">Polysilane</span>

Polysilanes are organosilicon compounds with the formula (R2Si)n. They are relatives of traditional organic polymers but their backbones are composed of silicon atoms. They exhibit distinctive optical and electrical properties. They are mainly used industrially as precursors to silicon carbide. The simplest polysilane would be (SiH2)n, which is mainly of theoretical, not practical interest.

Chlorotrifluorosilane is an inorganic gaseous compound with formula SiClF3 composed of silicon, fluorine and chlorine. It is a silane that substitutes hydrogen with fluorine and chlorine atoms.

Silanes refers to diverse kinds of charge-neutral silicon compounds with the formula SiR
4. The R substituents can any combination of organic or inorganic groups. Most silanes contain Si-C bonds, and are discussed under organosilicon compounds.

<span class="mw-page-title-main">(Trimethylsilyl)methyllithium</span> Chemical compound

(Trimethylsilyl)methyllithium is classified both as an organolithium compound and an organosilicon compound. It has the empirical formula LiCH2Si(CH3)3, often abbreviated LiCH2tms. It crystallizes as the hexagonal prismatic hexamer [LiCH2tms]6, akin to some polymorphs of methyllithium. Many adducts have been characterized including the diethyl ether complexed cubane [Li4(μ3-CH2tms)4(Et2O)2] and [Li2(μ-CH2tms)2(tmeda)2].

<span class="mw-page-title-main">Dodecamethylcyclohexasilane</span> Chemical compound

Dodecamethylcyclohexasilane is the organosilicon compound with the formula Si6(CH3)12. It is one of the more readily prepared and easily handled polysilanes. Dodecamethylcyclohexasilane is produced by reduction of dimethyldichlorosilane with sodium-potassium alloy:

References

  1. 1 2 Silicon: Organosilicon Chemistry. Encyclopedia of Inorganic Chemistry Online, 2nd ed.; Wiley: New Jersey, 2005. doi : 10.1002/0470862106.ia220
  2. 1 2 Rochow, Eugene G (1950). "Dimethyldichlorosilane". Inorg. Synth. 3: 56–58. doi:10.1002/9780470132340.ch14.
  3. 1 2 3 4 Polysiloxanes and Polysilanes. Encyclopedia of Inorganic Chemistry Online, 2nd ed.; Wiley: New Jersey, 2005. doi : 10.1002/0470862106.ia201
  4. ↑ Ulrich Lauter,† Simon W. Kantor, Klaus Schmidt-Rohr, and William J. MacKnight, Vinyl-Substituted Silphenylene Siloxane Copolymers: Novel High-Temperature Elastomers. Macromolecules. 1999, 32, pp 3426-3431. doi : 10.1021/ma981292f
  5. ↑ West, Robert; Brough, Lawrence; Wojnowski, Wieslaw (2007). "Dodecamethylcyclohexasilane". Inorganic Syntheses: 265–268. doi:10.1002/9780470132500.ch62. ISBN   9780470132500.
  6. ↑ Monjushiro, H. et al. "Size sorting of biological micro-particles by Newton-ring nano-gap device" Elsevier December 7, 2005
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.