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HALOSILANES WITH ALKYL AND hf ETHALLYL CHLORIDES 3601 "width" of the ring methylene line a t very fast exchange. The results are shown in Fig. 6. The activation energy obtained is AE = 6.4 i 0.6 kcal. and vo = 1 X lo9 set.-'.The measured activation energies for the two substituted 1-methylaziridines here investigated are very much smaller than most of the previous estimates and the experimental value obtained by Heeschen for 1-methylaziridine i t~e l f .~ It is interesting that our activation energies are quite close to the calculated value of 6 kcal. given by Manning'O for ammonia. The frequency factors, however, are much below the "normal" value of 1013, indicating that the transmission coefficients are much smaller than unity. This, however, is not too surprising in view of the similar order of magnitude for vo obtained for another "unimolecular" reaction of this type, namely, the rotation around the C-N bond in amides.11s12The effect of solvents on the inversion of I is shown in Figs. 4 and 5 . Both polar (methanol) and non-polar (carbon tetrachloride) solvents reduced the activation energy and frequency factor. It should be noted that the rate of inversion of I is considerably slower in methanolic solution than in the pure liquid or carbon tetrachloride. This has been attributed to the effect of hydrogen bonding between the hydroxyl group in methanol and the nitrogen atom in the aziridine ring.* However, it seems quite significant that the effect on such hydrogen bonding shows up in a greatly decreased (9) The reason for the sizable differences between the measured values A E for our compounds and I-methylaziridinea is not clear to us. It seems unlikely t h a t the rather small change in structure could ac-Count for all of the discrepancy, which appears to be well outside experimental error. (IO) M. F. Manning, J. Chem. Pkys., 3, 136 (1935). (11) H. S. Gutowsky and C. H. Holm, ibid., 26, 1228 (1956). (12) G. Fraenkel and C. Franconi, to he published.frequency factor rather than in an increase in activation energy. This may be due to a bimolecular mechanism for inversion in methanol solution where one methanol molecule attacks the rear of the nitrogen in an imine-methanol, hydrogenbonded complex.It is clear that further experimental and theoretical investigation of these processes would be very fruitful. . 67.8-68.2') was prepared by alkaline treatment of the sulfonate ester salt of 2-N-methylamino-2-methyl-1-propanol. 1-Methyl-2-methyleneaziridine (b.p. 52.2-52.6") was kindly supplied by Dr. A. T. Bottini.All measurements were taken with the Yarian model 4300B spectrometer. Frequency calibration was accomplished by the side-band technique. All measurements were performed at a proton frequency of 60 Mc., except those presented in Fig. 4, which were taken at 40 Mc. The measurements on pure I were taken at both 40 and 60 Mc.; the results were identical within the experimental accuracy.Two types of inserts for heating and cooling were used: (1) the type described by Shoolery and Roberts13 (supplied commercially ...

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The syntheses and chemical properties of some 54 compounds are described, all having structural units including ==SiCCCN= with either methyl, phenyl, siloxy, alkoxy, or amino groups on silicon and H, alkyl, or phenyl groups on nitrogen. Thirteen of the compounds are novel substituted heterocyclic l-aza-2-silacyclopentanes and one is a l-aza-2-silacyclohexane.