1,1′-(p-Phenylenedimethylene)dipiperidin-4-one

In the molecule of the title compound, C18H24N2O2, the piperidine rings are in chair conformations. The crystal structure is stabilized by intermolecular C—H⋯O hydrogen bonding. There are neither C—H⋯π nor π–π interactions in the structure.

In the molecule of the title compound, C 18 H 24 N 2 O 2 , the piperidine rings are in chair conformations. The crystal structure is stabilized by intermolecular C-HÁ Á ÁO hydrogen bonding. There are neither C-HÁ Á Á norinteractions in the structure.
VV thanks the DST-India for funding through the Young Scientist-Fast Track Proposal.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5127).
Potassium carbonate was filtered off and the excess solvent was removed under reduced pressure. The solid obtained was purified over a column of silica gel (60-120 mesh size) using benzene-ethyl acetate (60-80 °C) in the ratio of 20:80.

S3. Refinement
The H atoms were placed in calculated positions and allowed to ride on their carrier atoms with C-H = 0.93-0.97 Å.U iso = 1.2U eq (C) for CH and CH 2 groups.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.