| Autor: |
Egorov, Yu. P., Povolotskii, M. I. |
| Zdroj: |
Theoretical and Experimental Chemistry; November 1991, Vol. 27 Issue: 6 p609-615, 7p |
| Abstrakt: |
The changes in the chemical shifts of31P,13C, and29Si nuclei in structurally similar phosphaalkenes of the series XiP = C(SiMe3)2 have been investigated. The specific influence of the electrons of each of the four groups of substituents Xi on the delocalized p-system -P = C(SiE, SiZ) has been revealed. When the effect of conjugation (or hyperconjugation) from Xi is strengthened, the screening of the SiZ atom increases as the SiE atom loses its screening. In the case of Xi with a predominant inductive effect (halogens, uncojugated groupings) the changes in the screening of SiZ and SiE are symbatic. The correlations of the chemical shifts da with Hammett's s-constants and the behavior of the ionization potentials of the ?-and np energy levels in these compounds are discussed. It is assumed that the asymmetry in the degree of screening of the SiE and SiZ atoms is related to the participation of the unshared electron air of the P atom in the reaction with the -C(SiMe3)2 groupings. |
| Databáze: |
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| Externí odkaz: |
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