For ketimines and aldimines, respectively, the five core atoms (CC=NX and C(H)C=NX, X = H or C) are coplanar.  Planarity results from the sp-hybridization of the mutually double-bonded carbon and the nitrogen atoms.  The C=N distance is 1.29-1.31 Å for nonconjugated imines and 1.35 Å for conjugated imines.  By contrast, C-N distances in amines and nitriles are 1.47 and 1.16 Å, respectively.  Rotation about the C=N bond is slow.  Using NMR spectroscopy, both E- and Z-isomers of aldimines have been detected.  Owing to steric effects, the E isomer is favored.