Spectroscopic manifestations of the electronic effect of the substituent X in the molecules of (aroyloxymethyl)-trifluorosilanes and methyl (aroyloxymethyl) fluorosilanes 4-X-C₆H₄COOCH₂Si(Me)_3−nF_n

Conclusions

• 1. In the spectra of (aroyloxymethyl) trifluorosilanes and methyl (aroyloxymethyl) fluorosilanes with the general formula 4-X-C₆H₄COOCH₂Si(Me)_3−nF_n (n=1–3) the variation of the ΝC=O frequencies with variation of the substituent X in the aromatic ring is significantly larger in the spectra of the cyclic molecules with an intramolecular Si ↞- O coordination bond than for the acyclic molecules containing a free C=O group and a tetracoordinated silicon atom.

• 2. The frequencies for the stretching vibrations of the COC and SiF groups in the spectra of the molecules with the pentacoordinated silicon atom depend on the nature of the substituent X. Alternation between positive and negative values of the coefficient ρ is observed in the Hammett equations relating the frequencies and the σ_P values: ρ > 0 (ΝC=O, SiF_ax), ρ < 0 (ΝCOC).