Axial groups prevent racemization by blocking this process in molecules exhibiting atropoisomerism. Sigma-sigma-star hyperconjugation and steric effects are responsible for this process's namesake "barrier." Resonance (10[1])in the (10[1])amide portion of a peptide prevents this process from occurring. This process occurs along the (-5[1])x-axis, with energy plotted on the y-axis, of a relative energy diagram, which shows a series of peaks and valleys with accompanying Newman projections. This process converts ethane between eclipsed, staggered, and gauche forms. (10[2])Conformational isomers interconvert via this process, which cannot occur at double bonds. (-5[1])For 10 points, (10[1])name this (-5[1])process in which a molecule freely changes its torsion angle around a single bond. (10[1])■END■ (10[3])