Our work is focused on the relationship between molecular structure and crystal structure in organic compounds and its implications for solid-state reactivity. As part of that work, we have been examining two families of nitrogen-containing organic compounds, the benzylideneanilines (R-CH=N-R’, R = aryl) and the benzonitrile oxides (R-CN+-O-, R = aryl). We define bridge-flipped isomeric benzylideneanilines as those pairs that differ only in the reversal of the orientation of the imino linkage: R-CH=N-R’ vs. R-N=CH-R’. The relatively small size of the bridge hydrogen atom and the common occurrence of end-for-end disorder of the molecules in benzylideneaniline crystal structures suggest to us that isomorphism (identical solid-state molecular packing arrangements) should be possible for bridge-flipped isomeric benzylideneanilines. We are examining benzylideneanilines substituted with both halogen atoms and nitrile groups to determine whether similar intermolecular X-R-CN:…X-R-CN: Lewis acid-base interactions occurring in both members of a bridge-flipped pair can encourage their isomorphism. We are also preparing bis-benzylideneanilines capable of assuming centrosymmetric molecular conformations to determine whether or not the tendency of centrosymmetric molecules to occupy crystallographic centers of symmetry can encourage isomorphism. Our studies of crystalline benzonitrile oxides concern the solid-state reactivity of these compounds as a function of their ring substitution pattern. Which of three possible solid-state dimers may form and how readily they form are questions being explored. As part of that study, we have begun monitoring the solid-state reactivity of 3-bromobenzonitrile oxide and 4-nitrobenzonitrile oxide by infrared spectroscopy and are pursuing an X-ray crystal structure determination of one of the possible 3-bromobenzonitrile oxide dimers, the bis-(3-bromophenyl)furoxan.

Structures and reactivity of some nitrogenous organic solids

249th National Meeting (2015)

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