Rochow reaction

Effect of CuCl morphology and size on the activity in the Rochow reaction... 

Experimental details of the determination of kinetic data of the Rochow reaction are given in [6]. Briefly, the kinetic data of the synthesis reaction of silicon and methyl chloride (me)... 

Keywords Rochow Reaction / Active Copper Species / Promoter / Zinc / SEM / EDX... 

The catalytic activity of the Cu-Si surface species explained above was a logical, but only an indirect derivation from our former experiments. For some time, we were not able to present more direct evidence. The reason was the complicated surface topography of a working contact mass. According to all experiences, the Rochow reaction exclusively takes place in sharply demarcated pits on the silicon surface, the shape of which usually corresponds to the respective crystallographic planes. The inner surface of these pits mostly has an own structure, i.e, it is partly covered by particles of copper species, often doubtless by ri-CuaSi particles [15]. But, the characteristic dimensions of these structures are generally below the resolving power of appropriate surface methods like the combination SEM/EDX. 

In the following, these observations shall be interpreted in terms of a model, which in truth ascribes to the zinc promoter the role of a moderator of the Rochow reaction. 

On the whole, it seems that the famous promoter zinc acts in truth not as a real accelerator, as has been believed up to now, but as a kind of moderator of the initial reaction rate of the Rochow reaction and helps to maintain a sufficiently high stationary activity of a contact mass in this way. It is, of course, an open question, whether this mode of action also applies to other promoters and whether the promoter zinc can act also in other ways. 

Silicone Oils. Silicone refers to a siloxane polymer. The name itself derives from early research in which it was thought that oxygen was bound to silicon via a double bond such as found in a ketone. The simplest of these polymers are the poly(dimethylsiloxane)s. Poly(dimethylsil-oxane)s are made by hydrolyzing dimethyldichlorosilane with hydrochloric acid (9). Dimethyldichlorosilane is, in turn, made by the Rochow reaction. In this reaction, an alkyl halide (RX), methyl chloride in this instance, is treated with silicon metal in the presence of a catalyst (usually copper). The reaction results in a number of products that are separated by distillation (10). 

Mixtures of fluorine- or chlorine-substituted mono- and oligosilanes were obtained when SiO was reacted with aqueous HE and HCl gas, ° respectively, fri the case of the HCl reaction SiOz was claimed to be a byproduct. SiO was similarly reacted with organic halides in the presence of catalysts to give organosilicon chlorides, similar the Miiller-Rochow reaction of elemental silicon. ... 

Rochow reaction-based etching Etching (dry) Macroporous Zhang et al. (2014) 2014... 

Silicon—Carbon Bond-Forming Reactions. After the Rochow-MbUer direct process, the hydro silylation reaction (139),... 

In 1940 Rochow discovered the direct process, also cabed the methylchlorosilane (MCS) process, in which methyl chloride is passed over a bed of sibcon and copper to produce a variety of methylchlorosilanes, including dim ethyl dichi oro sil a n e [75-78-5] (CH2)2SiCl2. Working independently, Mbber made a similar discovery in Germany. Consequently, the process is frequently cabed the Rochow process and sometimes the Rochow-Mbber reaction. 

Organosilanes, especially dimethyldichlorosilane (M2), are important chemicals used in the silicone industries. The direct reaction of silicon with an organic halide to produce the corresponding organosilanes as a gas-solid-solid catalytic reaction was first disclosed by Rochow [1]. In the reaction, a copper-containing precursor first reacts with silicon particles to form the catalytically active component, which is a copper-silicon alloy, the exact state of which is still under discussion. As the reaction proceeds. Si in the alloy is consumed, which is followed by the release of copper. This copper diffuses into the Si lattice to form new reaction centers until deactivation occurs. The main reaction of the direct process is ... 

Reaction (2) was also studied using the different catalysts. Before exposure to CH3CI, the contact masses were subject to XRD analysis. In the XRD patterns of the catalysts with higher activities for the Rochow direct process, the XRD peaks of the Cu-containing species were weaker and broader when normalized to the silicon peaks (silicon was used in excess). This suggests that some undetectable species were formed and the catalytic species were well-dispersed. This agrees well with the view of Lieske and co-workers [5]. 

The evolution of methylchlorosilanes between 450 and 600 K is consistent with the 550 - 600 K typical for the catalytic Rochow Process [3]. It is also reasonably consistent with the evolution of methylchlorosilanes at 500 - 750 K reported by Frank and Falconer for a temperature programmed reaction study of the monolayer remaining on a CuaSi surface after catalytic formation of methylchlorosilanes from CHaCl at higher pressures [5]. Both of these observations suggest that the monolayer formed by methyl and chlorine adsorption on pure CuaSi is similar to that present on active catalysts. For reference, methylchlorosilanes bond quite weakly to tiie surface and desorb at 180 - 220 K. It can thus be concluded that the rate-determining step in the evolution of methylchlorosilanes at 450 - 600 K is a surface reaction rather an product desorption. 

Rochow et al. (29) also report that heating tri- and cyclotetrasilazanes under ammonia leads to the formation of linear oligo-dimethylsilazanes, reaction (12) however, they were never able... 

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. 

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 ... 

The first element, hydrogen, has an Allred Rochow electronegativity coefficient of 2.1, and an electronic configuration Is1. The atom may lose the single electron to become a proton, which exists in aqueous solutions as the hydroxonium ion, H30+(aq), in which the proton is covalently bonded to the oxygen atom of a water molecule. The ion is hydrated, as is discussed extensively in Chapter 2. The reduction of the hydrated proton by an electron forms the reference standard half-reaction for the scale of reduction potentials ... 

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