ELECTRONIC EFFECTS OF ME3SIOCR2 SUBSTITUENTS IN ACETYLENE DERIVATIVES

The sigma(R)(0) and sigma(p) parameters of Me3SiOCR2 and HOCR2 substit uents at the triple bond were determined using the IR spectra of indiv idual acetylene derivatives and their H-complexes. These parameters va ry as the effective charge on the atoms of the C-C fragment of termina l acetylenic alcohols and their trimethylsilyl ethers changes due to i ntermolecular interaction. The most reliable values of sigma(R)(0) and sigma(p) parameters (-0.02 and -0.03, respectively) for the Me3SiOCH2 substituent were established; they indicate a sharp decrease in alpha ,pi-conjugation of the Me3SiOCH2 substituent with the triple bond as c ompared to the Me3SiCH2 substituent.