The conjugation and effective charges of the atoms at the triple bond in germylacetylenes

Abstract

The integrated extinction coefficients (A) of the C≡C stretching modes in the IR spectra of 12 germylacetylenes Me3GeC≡CR are determined by the resonance interactions of substituents with the triple bond. TheA1/2 values change linearly with change in the difference between the effective π-electron charges on the atoms at the triple bond and σ0R constants of organic substituents R. The average value of the σ0R constant of the Me3Ge substituent in the compounds studied is +0.06. The resonance acceptor effect of the Me3Ge substituent toward the triple bond (d,π-conjugation) is stronger than the donor effect (σ,π-conjugation).