Determination of the Rotational Barrier of a Chiral Biphenyl: Comparison of Theoretical and Experimental Data

The rotational barrier of chiral 2-carboxy-2’-methoxy-6-nitrobiphenyl has been evaluated both by density functional calculation, at the B3LYP/6-31G(d) and B3LYP/6-311+G(d,p) leveles of theory, and by HF and post HF MP2 calculations at the 6-31G(d) level of theory. The DFT computed data, which seemed almost independent of the basis set used, are in good agreement with the values obtained from dynamic HPLC enantiomerization experiments and from the racemization rate constant of one of the enantiomers obtained by CD. The HF model seems to overestimate the barrier whereas the MP2 calculations confirm the DFT results.