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Investigation of Some Intramolecular Hydrogen Bonds by Nitrogen Magnetic Resonance Methods

Stefaniak L.

Polish Journal of Chemistry

1999

vol. 73 nr 1

173-180

It was shown that nitrogen NMR is a powerful tool in the studies of different types of hydrogen bridges (NHN)*, (NHN)-, (NHN), and (NHO). Some of the NMR parameters, originally proposed by us, provide information about charge redistribution and the extent of proton transfer. The character of hydrogen bonds depend upon solvent, temperature and the physical phase. The results of studies in the solid state using the 15N NMR CP MAS method were also discussed.

X-ray, IR and (1)H NMR studies of 1:1 adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) and 1,1-cyclobutanedicarboxylic acid (CBDC)

Bartoszczak-Adamska E., Grech E., Jaskólski M.

Polish Journal of Chemistry

1998

Vol. 72, nr 2

347-354

The crystal and molecular structure of the title compound has been determined by X-ray analysis. This compound crystallizes in the P2-1/c space group with cell parameters: a= 9.325(2), b=15.158(3), c=14.102(3) A, beta=106.40(3)degree and with four C14H19N(+/2)xC6H7O(-/4) formula units in the unit cell. The structure contains DMANH(+) cations with a short asymmetric intramolecular N-H...N hydrogen bond (N...N 2.595(2) A) and CBDC(-) monoanions with a short intramolecular O-H...O hydrogen bond (O...) 2.412(3) A). The ionic character of he very strog (NHN)(+) and moderately strong (OHO)(-) hydrogen bonds has been derived from IR spetroscopy. The (1)H NMR spectrum measured in acetonitrile solution is similar to that in the solid state.

FT-IR and NMR stedies of proton sponge character of Cis-1,2-bis(diethylaminomethyl)cyclohexane

Brzezinski B., Grech E., Klimkiewicz J., Schroeder G., Stefaniak L., Urjasz H.

Polish Journal of Chemistry

1998

Vol. 72, nr 2

284-291

Cis-1,2-bis(diethylaminomethyl)cyclohexane (DEAMCH) was synthesized and its pK-a values in acetonitrile were measured. Dual behevioral of DEAMCH was observed in the reaction with various acids: HClO4, 4-tert-butylphenol, 4-cyanophenol and pentachlorophenol (PCP) in acetonitrile and acetone-d-6 solutions, respectively, when studied by FT-IR as well as (1)H, (13)C and (15)N NMR spectroscopy. An intramolecular NHN(+) hydrogen bond was found in 1:1 complex of DEAMCH with HClO4 in solution. This hydrogen bond was, however, weaker than those previously observed in other protonated proton sponges. In complexes of DEAMCH with 4-cyanophenol both NHN(+) intramolecular hydrogen bond and structurally symmetrical intermolecular homoconjugated (OHO)(-) hydrogen bonds were formed. These properties of DEAMCH demonstrate its proton sponge like character. On the other hand, in complexes of DEAMCH with more acidic phenol such as PCP intermolecular hydrogen-bonded complexes are formed, in which the OH protons are localized at the amino groups. For these O(-)...HN(+) hydrogen bonds a strongly asymmetrical double minimum proton potential with the well at the N atom is present, characteristic of complexes having no proton sponge like character.