Contribution to the direct synthesis of phenylochlrosilanes

Abstract

.The preparation of alkyl-or ar).l-chlorosilancs!c~tcnsivcly studicd during thc last forty years; is carricd out mostly by allowing SiCl, to act eithcr on Grignard rcagcnts' or on alkyl-zinc or mcrcury-compounds.z Thc. Fittig-N'urtz mcthod(for the preparation of tetra-substituted dcriratc$was first utilized by Polis" and later by Kipping d Lloyd.' Schumb, Akcrmann and Saffcrf found it practical to prcpnrghc sodium organic dcrivativc scparatcly and then,d trcae.3 w6h thc silicon halide. Thc action of Grignard reagcgrs on ethyl silicate has bccn studied particularly by Russian chcmists.siSilicones have recently acquired a great importance, especially as far as their use as reliable high temperature (200-250°) electrical insulators is concerned.This has led to extensive researches concerning new methods of preparation which would be more convenient than those used at present in laboratories. Such researches, naturally, concern also the chemical Characteristics of the various substances involved, some of which were hardly known until recently. Generally speaking, silicones are the result of the polymerization of the hydrolysis products of organochlorosilanes ; thus, the most recent researches have been done particularly in view of the preparation of these halogenated compounds.The most interesting process is undoubtedly that of direct synthesis worked out by G. Rochow and hi6 co-workers in the laboratories of the General Western Company.' In this process alkyl-and aryl-halides in vapour state are brought in contact at a suitable temperature with elementary silicon, sometimes in [he presence of a metal which acts as a catalyst. A very complex reaction produces various halogen derivatives : R,SiCl, R,SiCl,, RSiCI, and SiCl,, which appear in percentage varying in dependence upon the conditions at which the process takes place and especially upon the type of catalyst used, the manner in which it is bound with silicon, the temperature, and the duration of the contact.The above mechanism is continued until the four valences of silicon are saturated. It is probable that a similar mechanism also governs the action of catalyst in the case of phenylderivatives. Although not actually proved, it is found in practice that the presence of a catalyst allows the process to be carried out at a lower temperature, and reduces the destructive action of the pyroscission process which comes next and leads to the formation of HCI, HSiCI, and SiCI,.In the case of phcnyl-derivatives, the synthesis adopted by Rochow, with the use at 430' of a soyo Si-Cu alloy aged artificially, leads mainly to the formation of (CaH5)SiCI,As we were interested chiefly in obtaining CoHSSiCI, and taking into account the fact that the action of HCI on Fe-Si alloys gives good yields of HSiCl,,' O we found it usefd to study the behaviour of a Si-Fe alloy (58% Si) more closely. ExperimentalIn a preliminary run chlorobenzene (dried over Na,SO, and rectified) was made to drip into an extremity of a reaction tube at c. 500". It was ascertained that under such condition...

Electroanalytical determination of antimony using electrocatalytic and enhancement phenomena

“…In his book entitled "Amperometric Titrations", Stock listed some of the applications of amperometry for the>determination of Sb(lll) (197)' Rechnitz reviewed the applications of controlled potential electrolysis (171). The available electrochemical techniques described are generally subject to interference from metal ions such as As (154, 162, 225), Bi (173), Cu (l45), Fe (l45), Pb (l42, 145, 212), and Sn (154). Elimination of the interfering species is usually done by precipitation (154,237) or with masking agents (87, 124,142).…”