Heteroaromatic rings as substituents. Part 5. Evaluation of σ and σ– constants of 2-selenienyl and 2-tellurienyl groups

Abstract

p- and m-2-selenienyl- and 2-tellurienyl-anisoles, p- and m-2-selenienyl- and 2-tellurienyl-phenols, and four 2,5-disubstituted tellurophens were synthesized and their structures established by ¹H n.m.r. and mass spectra. The σ^– and σ constants for p- and m-2-selenienyl and p- and m-2-tellurienyl were determined by the ionization reaction of monosubstituted phenols in 30% ethanol–water at 25 °C, by chemical shifts of the hydroxy-protons of phenols in DMSO, and by solvent chemical shifts of the methoxy-protons of anisoles. The 2-senenienyl and 2-tellurienyl groups are weakly, inductively electron-withdrawing and show greater ability to delocalize a negative charge by mesomeric effects. The results were compared with the substituent effects of 2-furyl and 2-thienyl.