The purpose of this study is to investigate intramolecular halogen bonding in non-activated systems and to determine if these halogen bonds can be detected through 13C NMR in solution. The control molecules in this study possess a 3-ethynlpyridine unit (A) that is incapable of halogen bonding between the nitrogen and X atoms because of the location of the nitrogen on the pyridine ring. However, an isomeric 2-ethynlpyridine-based system (B) is capable of halogen bonding because of the proper alignment of the nitrogen and halogen atoms. Comparison of 13C NMR chemical shifts of these molecules in benzene-d6 gives some indication of whether or not halogen bonding has occurred in the 2-ethynylpryidine systems. For example, the chemical shifts of the Cα and Cβ signals in A-I and A-Br are very similar. The chemical shifts of the Cα and Cβ signals of B-I and B-Br, on the other hand, vary due to differences in intramolecular halogen bonding in the benzene solution. Halogen bonding is indicated by a modest shielding of the Cα nucleus and a more significant deshielding of the Cβ nucleus. By utilizing intramolecular halogen bonding, this study probes the limits of halogen bonding in solution when entropic concerns are eliminated.

Intramolecular halogen bonding of non-activated aryl halides in solution

249th National Meeting (2015)

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