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Tautomeric Equilibria in Solutions of 1-Phenacylpyridazin-1-ium and 1-(o-Fluorophenacyl)pyridin-1-ium Cations. DFT and NMR Studies

Gawinecki R., Dobosz R., Ośmiałowski B., Zakrzewska A.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 9

1623-1628

EN

Although 1-(2-oxo-2-phenylethyl)pyridazin-1-ium and 1-[2-oxo-2-(o- fluoro phenyl - ethyl)]pyridin-1-ium cations may equilibriate with the respective enol and enaminone tautomeric forms, both experimental NMR data and results of ab in itio calculations show the keto forms to be the only species present in DMSO solution. Intramolecular hydrogen bonds and pi electron delocalization seem to have negligible effect on stabilization of the tautomers. On the other hand, electrostatic repulsions between the onium nitrogen and hydroxy oxygen atoms in the compounds studied are considered to be responsible for the in stability of the enol and enaminone tautomeric forms.

2

Tautomeric Equlibria (1,5-Proton Shift) in Simple Heteroconjugated Systems XH-A=B-C=Y X=A-B-CYH in Relation to Electron Delocalization

Ośmiałowski B., Raczyńska E. D., Gawinecki R.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 6

1093-1097

3

Stability of 1-Phenacylpyridinium and 1-(2-Hydroxy-2-phenylvinyl)pyridinium Cations

Ośmiałowski B., Janota H., Gawinecki R.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 2

169-177

4

Predominance of (E)-1,2-Di(pyridin-2-yl)ethene-1,2-diol over 2-Hydroxy-1,2-di(pyridin-2-yl)ethanone in Solution

Gawinecki R., Ośmiałowski B., Kolehmainen E.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 11

1411-1417

EN

1H, 13C and 15N NMR spectra, supported by the GIAO/DFT calculated (B3LYP/6- 311G//RHF/3-21G) 13C and 15N (B3LYP/6-31++G**//RHF/3-21G) NMR chemical shifts, show that (E)-1,2-di(pyridin-2-yl)ethene-1,2-diol (OO3) is the only tautomer present in chloroform solution. MP2/6-31G**//RHF/6-31G** and MP2/6-31G** ab initio calculations confirm that this perfectly planar form is really more stable than 2-hydroxy-1,2-di(pyridin-2-yl)ethanone (OK1, OK2 and OK3) and other isomeric dimers of pyridine-2-carboxaldehyde. The strong intramolecular hydrogen bonds are responsible for high stability of (E)-1,2-di(pyridin-2-yl)ethene-1,2-diol (the conjugation in the molecule is of minor importance).

5

Predominance of Amino-Sulfonyl Hydrogen Bonding in (Z)-2-Benzene-sulfonyl-1-phenyl-2-(phenylhydrazono)ethanones in Crystals adn in Solution: An Experimental NMR and X-ray Crystallographic and Theoretical Ab initio and DFT/GIAO Studies

Kolehmainen E., Zakrzewski A., Zakrzewska A., Nissinen M., Ośmiałowski B., Gawinecki R.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 1

31-45

EN

1H, 13C, and 15N NMR spectra show that (Z)-2-benzenesulfonyl-1-phenyl-2-(phenylhydrazono) ethanone is the only tautomeric form detected in chloroform solution. Substituent in the phenylhydrazone moiety does not affect this tautomeric preference. Ab initio calculations show that (Z)-2-benzenesulfonyl-1-phenyl-2-(phenylhydrazono)ethanone is really favoured over its proton transfer products in chloroform solution. This shows that N-H...OS(O) interaction is much stronger than the hydrogen bonds in other tautomeric forms. The (Z)-2-benzene-sulfonyl-1-phenyl-2-(phenylhydrazono)ethanone tautomer was also detected in the crystal state.

6

1H, 13C and 15N NMR Spectral and X-ray Structural Studies of 2-Arylsulfonylamino-5-chlorobenzophenones

Kolehmainen E., Nissinen M., Janota H., Gawinecki R., Ośmiałowski B.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 7

889-894

EN

Six 2-(4-R-phenylsulfonylamino)-5-chlorobenzophenones were prepared and their 1H, 13Cand 15NNMRspectra recorded and assigned. The dependence between the chemical shift of the amide proton and Hammett _ substituent constants is of the V type. Substituent effect on the chemical shift of the amide nitrogen atom was found insignificant. X-ray analysis shows that the terminal benzene rings in 2-(4-nitrophenylsulfonylamino)-5-chlorobenzophenone are located close to each other. They are not, however, parallel, dihedral angle between them being equal to 10.86 deg (MP2/6-31G**//HF/6-31G** ab initio calculations show this to be 20.44 deg). This shows that the mutual orientation of two benzene rings in the molecule of this compound is caused by the _-_ stacking. It is additionally reinforced by the intramolecular NH…O=C hydrogen bond. Except the dihedral angle between the benzene rings, X-ray determined structure of 2-(4-nitrophenylsulfonylamino)-5-chlorobenzophenone is very similar to this optimized by the ab initio calculations.

7

Solvatochromism of 1-(p-Aminostyryl)pyridium Salts

Gawinecki R., Trzebiatowska K.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 2

231-239

EN

Solvatochromism of eighteen 1-methyl-(p-aminostyryl)pyridinium perchlorates was studied. For each solvent the V~ max values follow the R o substituent constants of the amino groups present in the molecule. The V~ max values for compounds are usually highest and lowest in water and in methylene chloride, respectively. The substituent bathochromic shifts in some solvents are as large as 5700 cm-1. No inverted solvatochromism is observed. Analysis of the spectra do not confirm also this effect to be negative. Dependence between the band position and solvent polarity, hydrogen bond donor acidity and hydrogen bond acceptor basicity is of low quality. There is no simple relationship between the V~ max values and the solvent dielectric constants.