Structure of 2-cyano-4-phenyl-glutarimide studied by X-ray diffraction, vibrational spectroscopy and ab initio methods

The structure of 2-cyano-4-phenylglutarimide (3c) has been studied by single-crystal X-ray diffraction, infrared and Raman spectroscopies and ab initio methods. The crystals are monoclinic, space group P2₁2₁2₁, with a = 5.970(2), b = 8.569(1), c = 19.982(3) Å and z = 4. The X-ray diffraction study showed the presence of only one diastereomer of 3c, the relative configuration of which could be either S(C3)R(C5) or R(C3)S(C5), with both the cyano and phenyl groups in the equatorial positions. The crystal packing is stabilized by a network of weak intermolecular N-H ··· O, C-H ··· O and C-H ··· N hydrogen bonds. The molecular structure calculated at the HF/D95V** ab initio level is in excellent agreement with the one observed in the crystal. An assignment of characteristic infrared and Raman bands of 2-cyano-4-phenylglutarimide is reported.