¹³C FT‐NMR spectra of alkyl substituted furans. A study of the influence of steric interactions

Abstract

Abstract The 13 C FT‐NMR spectra of thirteen furans, monodi‐ or trisubstituted with methyl and/or t ‐butyl groups, were studied in detail. Substituent effects of methyl and t ‐butyl groups on the chemical shifts of ring carbon atoms are additive in nonsterically hindered furans. Steric shifts for the ring carbon atoms are found in furans with bulky neighbouring substituents, but the hybridisation of the carbon atoms in these hindered furans is not changed. The chemical shifts of the substituents are calculated according to the Grant‐Cheney formula. No simple relationship between steric shift and steric hindrance can be ascertained.