Solvent effects in NMR Spectroscopy : Solvent shifts of methoxyl resonances in flavones induced by benzene; an aid to structure elucidation

摘要: Abstract The position and relative orientation of OMe groups in methoxyflavones can be inferred from benzene-induced solvent shifts the resonances. at C-5, C-7, C-10 C-12 exhibit large positive Δ values (Δ = δCDC13 - δC6H6 ⋍ 0·5 to 0·8 ppm) absence substituents ortho these groups. In contrast, C-3, or those flanked by two ortho-OMe functions (or one ortho-OH orthoOMe function) show small negative values. An C-5 suffers a drastic algebraic decrease shift upon introduction an group C-6. Electronic conformational factors which may account for differences are considered.