Collect. Czech. Chem. Commun. 1981, 46, 873-882

IR spectra of some quinone methides. A study of the ortho-effect

Jiří Velek, Bohumír Koutek, Lubomír Musil, Soňa Vašíčková and Milan Souček

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6


Experimental values of frequencies and integrated intensities of carbonyl stretching vibrations in sixteen 2- and 2,6-substituted fuchsones were correlated with electronic substituent constants σ and steric parameters . For disubstituted fuchsone derivatives the ortho-effect is additive and is adequately described by the relationship *u(C=O) = 35.6 ΣσI - 9.1 Σ* + 1 625.5 (t = 0.982) and A(C=O)1/2 = -33.2 ΣσI - 1281 Σ* + 141.1 (r = 0.942). Wavenumber and integrated intensity of the carbonyl band decrease with increasing van der Waals volume of substituents. Contribution of the steric effect to the total transmission is substantially higher (about 30%) for 2,6-disubstituted than for 2-monosubstituted fuchsones.