1H NMR and FTIR studies of proton transfer reactions from C-acids to proton sponges

Abstract

Protonation of 1,2-bis(dimethylaminomethyl)benzene (DMAMB) and 1,8-bis(dimethylamino)naphthalene (DMAN) by various C-acids (1–5) in [²H₃]acetonitrile has been studied by ¹H NMR and FTIR spectroscopy. The mixtures of DMAMB or DMAN with C-acids in [²H₃]acetonitrile form protonated bases, complicated species, and homoconjugated nitro–aci-nitro (–NOO ⋯ H ⋯ OON–)^– hydrogen bonds. In the case of mixtures of DMAN with C-acids, a relatively slow chemical exchange in the ¹H NMR spectrum is observed, whereas for the corresponding mixtures with DMAMB the chemical exchange is much faster and only sharp signals of ring and methyl group protons are observed. The complex equilibria occurring in the mixtures of DMAMB or DMAN with C-acids are discussed on the basis of NMR and FTIR results.