Conformational analysis. A nuclear magnetic resonance study of the conformations of ortho-disubstituted benzenes
Results pertinent to the determination of the conformation of the side chain R1R2R3C attached to a benzene ring with or without an ortho-methyl substituent are reported and discussed. Results comprise dynamic n.m.r., carbon-13 chemical shift, and lanthanide-shift reagent data. When R1 is particularly large, the preferred conformation is concluded to be close to R1-perpendicular. In two cases two such conformations with either R2 or R3syn to the ortho-substituent are observed.