A theoretical analysis of the conformational space of tris(2-methylbenzimidazol-1-yl)methane

The conformation surface of tris(2-methylbenzimidazol-1-yl)methane has been explored locating four minima (uuu, uud, udd and ddd, each one corresponding to two enantiomers, the P and the M) and seven transition states. The known experimental barrier to racemization (119 kJ mol−1) was calculated to be about 110 kJ mol−1 (uuu or uud stereoisomers). GIAO calculations of absolute shieldings correlate very well with 1H and 13C NMR chemical shifts. Finally, the specific rotation of the four minima was calculated allowing us to identify the absolute configuration of the first eluted enantiomer.