Effect of Fused Benzene Ring on Rotational Barriers of 2,2’-Bifuran, 2-Phenylfuran, Biphenyl, and Their Benzo Analogues

Abstract

Molecular orbital (MO) calculations of torsional potentials of 2,2'-bifuran (F-F), 2-(2-furyl)benzofuran (F-BF), 2-phenylfuran (Ph-F), 2-(2-naphthyl)furan (Naph-F), 2-phenylbenzofuran (Ph-BF), biphenyl (Ph-Ph), 2-phenylnaphthalene (Ph-Naph), 2-phenylbenzo[1,2-b:4,5-b']difuran (Ph-BDF), and 2-phenylbenzo[1,2-b:5,4-6']difuran (Ph-BDF') by using HF/6-31G** and B3LYP/6-31G** methods have revealed that the rotational barriers are increased by 0.4-0.9 kcal/mol by replacement of the aryl moiety on the furan ring (furyl group of F-F and phenyl of Ph-F) with its benzo analogue. In contrast, increase of the rotational barriers is slight when the aryl moiety on the benzene ring (phenyl groups of Ph-F and Ph-Ph) is replaced with its benzo analogue and more extended π moiety.