Good data with `bad' reflections: the employment of non-spherical scattering factors in the redetermination of the structure of O-ethyl N-phenylcarbamate.

Abstract

The structure of O-ethyl N-phenylthiocarbamate, C₉H₁₁NOS (2), has been redetermined, confirming the results obtained in three earlier structure determinations. The higher data quality provided by modern diffractomers has enabled a reliable analysis (absent from the earlier reports) of the hydrogen bonding. However, conventional refinement of the structure of 2 was unsatisfactory because of the large number of extremely badly-fitting reflections, leading to many checkCIF `ALERT A' messages that might be detrimental to ease of publication. A refinement using nonspherical scattering factors effectively eliminated this problem. There are three independent molecules of 2 in the asymmetric unit; two are directly connected by two N-H...S hydrogen bonds, forming a dimer with the well-known R₂²(8) motif. The other molecule forms a topologically identical but inversion-symmetric dimer. Each type of dimer occupies a different region parallel to the ac plane (molecule 1, y ≃ 0; molecules 2 and 3, y ≃ 1/3 and 2/3). All three molecules lie in planes parallel to (031). The title compound is effectively isotypic to 1-ethyl-3-phenylthiourea (another known structure for which the hydrogen bonding was not analysed) because its EtNH group, like the EtO group of 2, is not involved in hydrogen bonding.