Chemical consequences of a polar axis in a solid-gas reaction. Reaction of p-bromobenzoic anhydride crystals with ammonia gas. The absolute direction of a polar unitropic reaction and the relationship of absolute configuration with crystal morphology

Polar Assembly of N,N‘-Bis(4-substituted benzyl)sulfamides

“…Given the diversity of the 4-substituents, the above results are very surprising. The polar packing of 1b − g is to some extent similar to the previously reported layered crystal structures of 4-bromobenzoic anhydride, which was reported to pack in the noncentrosymmetric space group C 2 . However, 4-substituted benzoic anhydrides did not demonstrate the type of generality in forming polar solid-state structures as shown by 1b − g .…”

“…However, 4-substituted benzoic anhydrides did not demonstrate the type of generality in forming polar solid-state structures as shown by 1b − g . For example, 4-chlorobenzoic anhydride was reported to crystallize into the centrosymmetric group P 2/ c 10a. In fact, our results represent the first example of a homologous series of achiral compounds that undergo spontaneous resolution in the solid state and crystallize into the same noncentrosymmetric group …”

Chemical consequences of the polar axis in organic solid-state chemistry

“…In Figure 9 is shown a crystal photographed at various stages of reaction. 23 In this case initiation of the reaction is favored at a single side of the crystal and occurs preferentially in a direction parallel to the b axis; in other words, the polar axis of the crystal directs the reaction. The selectivity can best be seen in small crystals relatively free from defects.19 These observations fail to show, however, whether the reaction proceeds along the polar axis by approaching the anhydride groups from the side of the carbonyl oxygen atoms or from the opposite side of the carbonyl carbon atoms.…”

“…In fact, the crystal morphology has been correlated with the absolute configuration so that the configuration can be assigned by visual inspection of the crystal. 23 Although in solution the enantiomeric anhydride molecules are in rapid equilibrium with each other, it should be possible to utilize the molecular chirality of p-bromobenzoic anhydride in the crystal by carrying out reaction in such a way that the conformation is frozen until the instant when reaction occurs-as in, for example, the reaction of crystalline anhydrides with gaseous reagents. Thus, the chirality of crystalline p-bromobenzoic anhydride might be used to resolve a racemic gaseous amine by virtue of the preference of the chiral anhydride for reaction with one of the amine enantiomers rather than the other.…”

N-Phenylanthranilic anhydride

“…For the synthesis, see: Martín et al (2006); Wiklund et al (2004). For related structures, see: Duesler et al (1981); Huelgas et al (2006). independent and constrained refinement Á max = 0.25 e Å À3 Á min = À0.20 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).…”