Molecular Structure of CCl3NO2 by Electron Diffraction

The structure of chloropicrin, an unstable compound, has been studied by electron diffraction, using the sector‐microphotometer method. Final parameters have been obtained by means of a least‐squares fit of a structural model to the experimental intensity curve. The structure is similar to those found previously for fluoropicrin and bromopicrin. The −CCl₃ group and the N–O bond have the expected values for bond lengths and angles. However, the C–N distance is very long, 1.594 Å; the ONO angle is 131.7°; the −CNO₂ group is not planar; and the molecule assumes a staggered conformation similar to that found in ethane compounds with one position vacant. On the basis of a potential function of the form $\mathrm{V=}\frac{1}{2}{V}_0\text{(1−A}\cos \text{3φ−B}\cos \text{6φ)}$ , where 0.75≤A≤1.0 and A+B=1, a barrier of 2.70–3.35 kcal/mole hindering free rotation about the C–N bond has been found.