826
JOHN
PRODUCTS PROM Formula
B.p., " C . a t 749 mm.
THE
L. SPEIER TABLE V CHLORINATION d%
nlju
Vol. 73
OF
Me,SiCH2C1 Mole %
h.leaSiCH2C1" Me3SiCHClnh MeaSiCCl: Me2Si(CHzC1)2h Me2SiCH2C1CHCI;
97.2 133-134 146-156 16G-161 183-181
1.4148 1.4430 hl. p. 60-66' 1,4573 I ,475:;
0.8765 1.0-1. 1.08 1,208
35.5 20.0 1.3 30.5 8.5
MeSi( CH2CI)Sc
205
1 ,-4857
1.24
2.1
Calculated
Sp. ref.
0.2865 0.2544 % a , 55.54 0.2544 0.2338 YiCl, 55.54 0.2338 %a, 55.54
Found
0.2856 0.254 55.4 0.253 0.2330 55.45 0.231 55.53
Residue as SiC4HnCI, 1.490 1.1 Total 99.0 F. C. Whitmore and L. H. Sommer, THISJOURNAL, 68, 481 (1946), report: b.p. 97.1" a t 734 mm., n3D 1.4180, dZbr 0.8791. * J . L. Speier and B. F. Uaubert, ibid., 70, 1400 (1948), report for MeaSiCHC1z, b.p. 133" a t 730 mm., dSr 1.0395, h.p. 160' a t 724 mm., ds, 1.075, n s ~1.4579. These were previously unreported comItZ5D 1.4430; for Me2Si(CH2C1)*, pounds. Their configurations were assigned on the basis of their boiling points.
the rates of chlorination for the substitution of the first chlorine were nearly identical for the analogous structures Me3CCl and Me&3iC1, but the presence of less Me2C1SiCH2CIthan hle2CICCH2C1 showed again that the former was chlorinated more rapidly than the latter. Experimental. Chlorination of MeJSiCH2C1.-Two moles of chloromethyltrimethylsilane (b.p. 97.2' a t 740 mm., T Z * ~ D 1.4148, 245 9.) was chlorinated until it weighed 300 g. Approximately 1.6 moles of chlorine were used. The products were then distilled carefully and the products listed in Table V were found.
Discussion.-The chlorination of chloromethyltrimethylsilane revealed that in this compound no unusual orientation effects of silicon were apparent. The most symmetrical products were the chief ones formed as is typical of hydrocarbon chlorinations. The chlorination of t-butyl chloride
[CONTRIBUTIOSFROM
gave a ratio of Me2CC1CHCl2/MeCC1(CH2C1)2 = 0.6'7. The ratio of MesSiCHClz/MezSi(CH2C1)2 = 0.66. The symmetrical trichloride was obtained, and this is the first example of such a structure ever reported. No trace of the corresponding structure from trichlorosilane has ever been found. The typical hydrocarbon character toward chlorination of the chloromethyltrimethylsilane shows that silicon alone is not responsible for the anomalous distribution of products obtained from methylchlorosilanes. The halogen is essential on silicon if the effect is to be noted. Probably other negative substituents on silicon give rise to the same phenomenon, and we have qualitatively observed this same distribution in chlorinated methylsiloxanes. PITTSBURGH 13, PA. RECEIVED AUGUST 21, 1950
THE b f E L L O N INSTITUTE]
Bromination of Methylchlorosilanes HY JOHN L. SPEIER A solution of bromine in compounds difficult to brominate reacted smoothly in the presence of chlorine and light to yield brominated derivatives. The process was equally applicable for brominating hydrocarbons such as benzene, toluene and cyclohexane as for methylchlorosilanes. New compounds described were : bromomethyltrimethylsilane; bromomethyldimethylchlorosilane; bromomethylmethyldichlorosilane; dibromomethylmethyldichlorosilane; sym-bis-(bromomethy1)tetramethyldisiloxane; bromomethylpentamethyldisiloxane;brornophenyltrichlorosilane.
Except ;or one instance, a thorough search of the literature revealed no reference concerning the direct bromination of organosilicon compounds. E. Larsson and L. 0. Knopp' have brominated tetraethylsilane a t reflux temperature with bromine. A similar procedure using trimethylchlorosilane, dimethyldichlorosilane or hexamethyldisiloxane produced no reaction in this Laboratory. The addition of chlorine to a solution of bromine in any of these or related compounds caused immediate reaction to occur with the formation of only brominated organosilicon compounds and hydrogen chloride. No carrier or catalyst of any kind was found necessary. (1) E Larsson and I, 0 Knopp, A c f o Chcm Srand , 1, 268 (1947).
Remick2states that bromine chloride is a powerful brominating agent. This is true, but a reasonably thorough literature search brought t o light no examples of bromine chloride as a brominating agent until McBee, Sanford and Graham* used i t with a carrier t o brominate trifluoromethylbenzenes. The reagent is excellent for the bromination of methylsilicon compounds as well as for many organic compounds. The bromine in some cases is nearly quantitatively converted to bromides. (2) A E. Remick, "Electronic Interpretation ofOrganic Chemistry," J. Wiley and Sons, Inc.. New York, N. Y , 1943, p 129. (3) E T. McBee R A Sanford and E'. J. Graham, TEISJOURNAL,
TZ, 1851 (1980).
Feb., 1951
BROMINATION OF
METHYLCHLOROSILANES
527
silane was obtained, h.p. 115.5' a t 742 mm., %*D 1.44221.4424, dsd 1.170, sp. ref. 0.2254, calculated4 sp. ref. 0.2272. Anal. Calcd. for C,HllBrSi: Br, 47.9. Found: Br, 47.7. A product of the same properties was prepared more easily by brominating tetramethylsilane. Bromomethylmethyldichlorosilane and DibromomethylExperimental (2 moles) Bromination Using Bromine and Chlorine.-The follow- methyldich1orosilane.-Dimethyldichlorosilane (1 equiv.) by the same technique with bromine ing technique was employed in every case. As an example bromomethylmethyldichlorosilane, b.p. 140-141 yielded a t 740 the bromination of trimethylchlorosilane will be described mm., n% 1.4750, d*4 1.57, sp. ref. 0.179; calculated sp. in detail. 0.1789; yield 34%. Anal. Calcd. for CZHbBrC12Si: ref. Bromomethyldimethylchlorosilane.-TrimethylchloroC1, 34.10. Found: C1, 34.5. Dibromomethylmethyldisilane (119 g., 1.1 moles) was illuminated with a 60-w. in- chlorosilarie was also obtained, b.p. 86-91' at 25 mm., nS.% candescent lamp in a 500-ml. flask equipped with a reflux 1.5185; yield 24.8%, based on bromine used. Steam dlscondenser topped by a Dry Ice cooled knock down conden- tillation of this compound from 5% aqueous sodium hyser. From a separatory funnel a small amount of bromine droxide yielded methylene bromide, b.p. 95" a t 742 mm., was added. Chlorine was then passed through the mixture 2.4, n% 1.5290, sp. ref. 0.128, calculated, sp. ref. 0.127; until the dark red color of bromine disappeared. More du4 yield 86%. The isolation of methylene bromide established bromine was then added and the process was continued until the configuration of the brominated silicon compound. 46.5 g., 0.64 equivalent, was added. The mixture then The higher boiling products were a crystalline mixture which weighed 168 g. According t o the equation 2RH C12 was not separated. Br, + 2RBr 2HC1 the product should weigh 169 g. Bromomethylpentamethy1disiloxane.-Hexamethyld iThe gases that escaped the condensers were trapped in siloxane (286 g., 1.76 moles) similarly brominated with 1.54 aqueous alkali. Qualitative analysis showed no bromide equivalents of bromine yielded bromomethylpentamethylin the trap a t the end of the experiment. The product was disiloxane, b.p. 83' a t 49 mm., #D 1.4279, dud 1.097, sp. distilled and yielded 61 g., 51y0 of recovered trimethylref. 0.2345, calculated sp. ref. 0.2347; yield 25%. Anal. chlorosilane ; no trace of trimethylbromosilane; a possible Calcd. for CsHITOBrSi: Si,.23.3; Br, 33.1. Found: Si, trace of chlorornethyldimethylchlorosilane,and in addition 23.1; Br, 34.5. Higher boding isomeric dibromides were to a residue of polybrominated products, 75 g. of bromo- obtained (28 9.) b.p. 72-104' a t 16 mm. which were exmethyldimethylchlorosilane, b.p. 130' a t 740 mm., n a b tremely active lachrymators. This fraction turned dark and 1.4630, dS4 1.375, sp. ref. 0.2002, calculated4 sp. ref. soon after distillation. It obviously decomposed 0.2005; yield 62% based on bromine. Anal. Calcd. for fumed on storage before it was to be analyzed. Higher boiling C3H8BrC1Si: C1, 18.91. Found: C1, 18.83. fractions were also obtained, all of which appeared t o be disym-Bis-brornomethyltetramethy1disiloxane.-A sample and tribromides. No pure compounds were isolated from of bromomethyldimethylchlorosilane so obtained was hy- this high boiling mixture. The lachrymatory properties drolyzed by shaking it with water. The aqueous layer was of these fractions probably may be associated with two or tested qualitatively for bromide ion. None was found. more bromide substituents on the same carbon. Pure bisTherefore, no readily hydrolyzable bromine was present shows no such activity. and no isomer such as chloromethyldimethylbromosilane bromomethyltetramethyldisiloxane Other Brominations.-The procedure was used on hydrowas present. The hydrolysate was washed with water, carbons usually with the hydrocarbon :bromine ratio of separated and dried over sodium sulfate. With no further 2 : l . The following results were obtained with the yields Durification svnz-bis-(bromomethvll -tetramethvldisiloxane based on bromine: toluene yielded 71 Yo benzyl bromide; Gas obtained &th t h e following Goperties ; b.p. 232-235' cyclohexane yielded 45% cyclohexyl bromide, and 38% a t 734 mm., n% 1.4719, dZ541.3918, sp. ref. 0.2004, cal- cyclohexyl dibromides ; benzene yielded 68% bromobenzene ; d a t e d 4 SD. ref. 0.2008. Anal. Calcd. for c 6 H d B r ~ S i : phenyltrichlorosilane yielded 40% bromophenyltrichloroSi, 17.53. Found: Si, 17.5. BromomethyltrimethylsUane.-A sample of bromomethyl- silane, b.p. 126-128' a t 23 mm.6 Anal. Calcd. for GH4dimethylchlorosilane was treated with 10% excess methyl- BrCllSi: C1,36.6. Found: C1,36.6. magnesium bromide in ether. Worked up in the usual ( 5 ) G.Gruttner and E.Krause, Bcr., 60,1559 (1917),report LL b.p. of manner, a yield of 80% of theory of bromomethyltrimethyl1 2 3 O at 15 mm. for 9-bromophenyltrichlorosilane.
Very little, if any, hydrogen bromide is produced. The reaction is easily carried out on either aliphatic or aryl hydrocarbons as well as on silicon compounds.
+
(4)
E.L. Warrick, THISJOURNAL, 68, 2455 (1946).
+
+
PITTSBURGH
13, P A .
RECEIVED AUGUST21, 1950
