FT-IR AND NMR-STUDIES OF THE PROTON SPONGE CHARACTER OF CIS-1,2-BIS(DIETHYLAMINOMETHYL)CYCLOHEXANE

Cis-1,2-bis(diethylaminomethyl)cyclohexane (DEAMCH) was synthesized an d its pK(a) values in acetonitrile were measured. Dual behaviour of DE AMCH was observed in the reaction with various acids: HClO4, 4-tert-bu tylphenol, 4-cyanophenol and pentachlorophenol (PCP) in acetonitrile a nd acetone-d(6) solutions, respectively, when studied by FT-IR as well as H-1, C-13 and N-15 NMR spectroscopy. An intramolecular NHN+ hydrog en bond was found in 1:1 complex of DEAMCH with HClO4 in solution. Thi s hydrogen bond was, however, weaker than those previously observed in other protonated proton sponges. In complexes of DEAMCH with 4-cyanop henol both NHN+ intramolecular hydrogen bond and structurally symmetri cal intermolecular homoconjugated (OHO) hydrogen bonds were formed. Th ese properties of DEAMCH demonstrate its proton sponge like character. On the other hand, in complexes of DEAMCH with more acidic phenol suc h as PCP intermolecular hydrogen-bonded complexes are formed, in which the OH protons are localized at the amino groups. For these O- HN+ hy drogen bonds a strongly asymmetrical double minimum proton potential w ith the well at the N atom is present, characteristic of complexes hav ing no proton sponge like character.