Protonation of 1,8-bis(dimethylamino)naphthalene by various acids in acetonitrile

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Abstract
FTIR studies on a number of systems composed of 1,8-bis(dimethylamino)naphthalene (DMAN) and various organic acids (phenols, benzoic acid derivatives and dicarboxylic acids) were carried out. The degree of protonation was estimated based on the intensity of the Bohlmann bands. In the ionic equilibria the homoconjugated anions play an essential role so that the degree of protonation depends on the excess of acid. The 1:1 complexes of phenols and benzoic acids in acetonitrile form a mixture of protonated DMAN, free DMAN, homoconjugated anions and more complicated species. The broad absorption extending over the whole IR region results from the combination of bands ascribed to ν(NHN+) of protonated DMAN and ν(OHO–) of homoconjugated anions.