The effects of the solvent and temperature on the interconversion between the α-side-exo-substituted[3333]-2-one (A) and α-corner-syn-substituted[3333]-2-one (B) conformations of the α-monosubstituted cyclododecanoneshave been studied by means of ¹H NMR technology. The result shows that increasing the polarity of the solvent generally increases the population of the conformation B owing to the higher dipole moment of the conformation B than that of A. By contrast, in the case of the monosubstituted cyclododecanones with an intramolecular hydrogen bondbetween the substituent and the carbonyl group, increasing the polarity of thesolvent decreases the population of the conformation B owing to the weakening of the intramolecular hydrogen bond. The result also shows thatraising temperature is favourable to the interconversion of two conformations,achieving a new equilibrium.

Key words: α-monosubstituted cyclododecanone, conformation, conformational interconversion, α-side-exo-substituted[3333]-2-one conformation, α-corner-syn-substituted[3333]-2-one conformation