The Crystal Structure of Securinine Hydrobromide Dihydrate and the Molecular Structure of Securinine

X-ray crystal structure analysis has been made on the securinine hydrobromide dihydrate, which is monoclinic, with two formula units in a cell of dimensions : α=7.71Å, b=14.83Å, C=7.04Å, and γ=112.13°. The space group is P21. The determination of the atomic parameters was carried out by the generalized projection methods. The conclusions may be summed up as follows : The piperidine ring has a skewed boat form, and the diene part is not co-planar. A dihedral angle of about 10°has been found between the plane passing through C2-, C3-, and C3a-atoms and the one involving C3a-, C4-, and C5-atoms. Discussion has been made on the location of the lone electron pair on the nitrogen atom in the free base.