AbstractThe conformation of ε‐caprolactam (1‐azacycloheptan‐2‐one) was studied by low‐temperature 2 D1H and13C NMR. Only one conformer was found in solution from the13C NMR spectra recorded down to −155°C. This conformer was shown, by infrared spectroscopy, to be the same as that found in the crystals of ε‐caprolactam. A conformational process with a free energy of activation of 43 kJ mol−1, coalescence temperature −65°C, was interpreted as geminal1H exchange. The assignments of the13C and1H shifts were made by 2 D NMR. Splitting of all averaged signals for geminal protons into axial and equatorial signals was d