Rochow-Muller process

The synthesis of organosilicones and organosilicone surfactants has been well described elsewhere [36-39] and hence only a brief review is given here. Industrially the manufacture of silicones is performed stepwise via the alkylchlorosilanes, produced through the reaction of elemental silicon with methyl chloride (the Muller—Rochow Process) [40,41]. Inclusion of HC1 and/or H2(g) into the reaction mixture, as in Eq. (1.2), yields CH3HSiCl2, the precursor to the organofunctional silanes, and therefore the silicone surfactants ... 

Catalytic (Lewis base-induced) disproportionation of tetrachlorodimethyldisilane or dichlorotetramethylsilane is another efficient process to generate oligomeric silanes without formation of solid by-products. - ° The inexpensive starting compounds are obtained as a by-product during the synthesis of chlorosilanes in the Muller-Rochow process. Depending on the molecular structure, that is, the number of chlorine atoms per silicon atom, mixtures of linear or branched polymers form. 

The main commercial use of solid SiO is as a vapor-deposition material for the production of SiOx thin films for optical or electronic applications (antireflective coatings, interference filters, beam-splitters, decorative coatings, dielectric layers, isolation layers, electrodes, thin-film capacitors, thin-film transistors, etc.), for diffusion barrier layers on polymer foils or for surface protection layers.Other uses for SiO have been proposed, such as the substitution of elemental silicon in the Muller-Rochow process for the production of organosilicon halides, because solid SiO can be produced at lower temperatures than elemental silicon. 

This contribution to the broad field of organosilicon chemistry including molecules and materials, marks a very unusual anniversary, the existence of which effectively contradicts a historical statement by the famous organosilicon pioneer F. S. Kipping, who believed 80 years ago that organosilicon chemistry would never gain industrial and commercial importance. Fifty years after the invention of the Miiller-Rochow process, the silicon industry achieved an annual worldwide turnover of US 4.700.000.000. This proves impressively that the basic process - independently developed by R. Muller and E. G. Rochow in 1941/2 - can be considered to be the most important innovation for organosilicon research work in industry and university. 

Silanes, siloxanes, and silicones are commercially produced from silicon and methyl chloride in a process known as the direct reaction or the Rochow-Muller direct process. ... 

The F3 cyclic species is obtained through hydrolysis of the corresponding silane, methyl(3,3,3-trifluoropropyl)dichlorosilane. This silane is the hydrosilylation adduct of 3,3,3-trifluoropropene and methyldichlorosilane, CH3HSiCl2, a minor product of the Rochow-Muller direct process for manufacturing methylchlorosilanes. The hydrosilylation reaction is catalyzed with transition metal complexes of platinum or rhodium such as Speier s catalyst and hexachloroplatinic acid in isopropanol. The reaction conditions are very similar to those employed with unfluorinated reagents, complicated only by the fact that 3,3,3-trifluoropropene is a gas. 

More than 60 years after its simultaneous discovery by Rochow and Muller, the direct reaction of copper-activated silicon with alkyl chlorides is arguably still the most important industrial process for the preparation of basic organosilanes. An inspiring historic account highlighting the significance of this seminal work has been given by Seyferth.12 A comprehensive review on the subject has been written by Jung and Yoo.13 The most recent work associated with the direct process is concerned with the role of metallic promoters, such as Zn and Cd, as well as mechanistic aspects.14... 

The example of the first category is the formation of alkyl- and arylchlorosilanes in the so-called direct process (DP). The process was discovered over 60 years ago by Rochow in the United States, and, independently, by Muller in Germany, and it is still the most important reaction in organosilicon chemistry. In fact, it is at the very basis of the silicone industry, being the primary source of organochlorosilane precursors (mostly methylchlorosilanes, comprising over 90% of the total) in the production of silicone oligomers and polymers. 

A common feature of all these compounds is their tetrahedral structure at the silicon atom which is bound to four oxygen neighbors. A tremendous breakthrough in the history of silicon-based polymers has been achieved by the invention of the Direct Process by Muller and Rochow resulting in the industrial production of methyl chlorosilanes with hydrolytically stable Si-C bonds besides very reactive Si-Cl bonds which serve as building units for a wide variety of polydimethyl siloxanes including silicon fluids, resins, and elastomers. 

Of special interest are molecules possessing n electrons only in combination with o bonds. The reactions of silicon atoms with target molecules of this type are relevant for the understanding of the Rochow-MUller (R.-M.) synthesis [2]. In a recent essay Seyferth describes the enormous importance of this direct synthesis of dichlorodimethylsilane by reaction of a silicon/copper alloy with methyl chloride [3]. At the same time he points out that even today, more than 60 years after its discovery in 1940, the mechanism of this process is still not fully understood. It was our hope... 

Summary The Direct Process discovered by Rochow and Muller around 1940 is the basic reaction used to produce methylchlorosilanes, which are the monomeric intermediates used for production of silicones. An understanding of the elementary reactions, the nature of active sites and the action of promotors does not nearly come close to the performance level of the industrial process and the economic importance. The silylene-mechanism is a useful model to understand the complex product mixture from the reaction of silicon with chloromethane. 

The Direct Process is the reaction of silicon with chloromethane to form methylchlorosilanes (Eq.l). This reaction is unique, in that it is the only solid-catalyzed gas-solid reaction applied in the chemical industry. The Direct Process was first discovered by Rochow [1] and independently Muller [2] around 1940. 

Organohalosilanes are industrially produced by direct synthesis from silicon and alkyl- or aryl-halides in the presence of copper or silver catalysts using a process developed by Rochow and Muller in 1941/42. 

The great industrial process for the production of alkylchlorosilanes is the heterogeneous Rochow-Muller process whose mechanism remains somewhat obscure. Essentially dialkyldichlorosilanes are produced in the mixture RnSiCl4 n(n = 1-4) ... 

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