Aug. 5 , 1956
PREPARATION AND PROPERTIES OF NEGATIVELY-SUBSTITUTED ORGANOSILANES 3835 [CONTRIBUTIONFROM
THE
WESTINGHOUSE RESEARCH LABORATORIES]
Preparation and Properties of Some Negatively-substituted Organosilanes BY LAWRENCE W. FROST RECEIVED JANUARY 27, 1956 The preparations of several organosilanes containing fluorinated organic groups are reported, together with their dielectric constants, dissipation factors, viscosities and usual physical properties. The preparations and physical properties are also given for the precursors which have not been previously reported. Melting points of mixtures of 4-chloro-3-(trifluoromethyl)-phenyltrimethylsilaneand bis-[4-chloro-3-(trifluoromethyl)-phenyl]-dimethylsilane are also reported.
Several (trifluoromethy1)-phenylsilanes have been prepared to be used in a study of stable liquids of high dielectric constant. This paper reports the preparation and some physical properties of these compounds and of some of their precursors. 3-(Trifluoromethy1)-phenyltrimethylsilane, 4chloro - 3 - (trifluoromethyl) - phenyltrimethylsilane, and bis- [4-chloro-3-(trifluoromethy1)-phenyl]-dimethylsilane were prepared from chlorotrimethylsilane or dichlorodimethylsilane and the appropriate substituted phenylmagnesium bromide. 3Trifluoromethylbenzyltrimethylsilane was prepared from 3-trifluoromethylbenzylmagnesium chloride and chlorotrimethylsilane. Because of the difficulty of obtaining 2- and 4-bromo-(trifluoromethyl)benzene, 2-(trifluoromethy1)-phenyltrimethylsilane was prepared by the following reaction scheme and 4-(trifluoromethy1)-phenyltrimethylsilane by a similar one in which the chlorination and the first fluorination steps were interchanged. CH3 I
CCl, I
CHI I
CF3 I
CHa I
CS 1
1.31 Attempts to prepare 2- (trichloromethy1)-phenyltrichlorosilane by chlorination of 2-methylphenyltrichlorosilane were unsuccessful, presumably because of steric hindrance. A similar hindrance has been observed in attempts to prepare 1,2-bis(trichloromethy1)-benzene. The chlorination of 2-methylphenyltrifluorosilane, however, proceeded easily to give 2-(trichloromethy1)-phenyltrifluorosilane. The conversion of 4- (trichloromethy1)-phenyltrichlorosilane to 4-(trifluoromethy1)-phenyltrifluorosilane can be done in one step, but better yields were obtained by a two-step process with purification of the intermediate (trichloromethy1)phenyltrifluorosilane. Physical properties are given in Tables I and I1 for those compounds which have not been reported previously, The high dielectric constant of bis- [4-chloro-3(trifluoromethy1)-phenyl]-dimethylsilanemade it of interest in this program, but it was unsuitable ( 1 ) 0. Scherer, W Schumacher and I; >fuller, U. S Patent 2,121,330 (1938)
because of its high melting point. Consequently, several mixtures were made of this compound with various proportions of 4-chloro-3-(trifluoromethyl) phenyltrimethylsilane, and their melting points were determined from warming curves. Attempts to use cooling curves were less successful because of supercooling and very slow crystallization. The phase diagram obtained is shown in Fig. 1. Data in the region between 60 and 90% of 4-chloro-3(trifluoromethy1)-phenyltrimethylsilane were not obtained because all efforts to induce crystallization of these mixtures failed. The eutectic point appears to be a t approximately 90% 4-chloro-3(trifluoromethy1)-phenyltrimethylsilane, with a melting point of about -41'. TABLE I PHYSICAL PROPERTIES OF SOMENEGATIVELY SUBSTITUTED SILANES Compound 2- (CHa)-CaH4-SiCla 2- (CHa)-CaH&iFa 2- (CCl)a-CaH&iFa 2- (CFa)-CaH&iFa Z-(CFs)-CsH,-Si(CHa)a 4-(CCls)-CaHc-SiCls 4-(CCla)-CsHeSiFa 4-(CFs)-CaH4-SiFa 4-(CFs)-CaHc-Si(CHa)a 3- (CFa)-CsH&i( CH3)r 3- (CFa)-CaH4-CHn-Si(CHa)r 4-CI-3-(CFs)-CaHs-Si(CHa)a (CHa)?[4-Cl-3-(CFa)-CaHs]zSi
B.P., M.P., OC. OC. 226.7 -25 to -26 130.8 < -78 229.0 -9 to -10 -36 to -38 138.0 185.5 < - 7 8 67.5-68.0 212.2 5-5.5 3 to -4 118.6 - 23 180.7 175.1
