ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAromaticity as a quantitative concept. 1. A statistical demonstration of the orthogonality classical and magnetic aromaticity in five- six-membered heterocyclesAlan R. Katritzky, Piotr Barczynski, Giuseppe Musumarra, Danila Pisano, Miroslaw SzafranCite this: J. Am. Chem. Soc. 1989, 111, 1, 7–15Publication Date (Print):January 1989Publication History Published online1 May 2002Published inissue 1 January...

Abstract AM1 and PM3 semiempirical calculations are reported for the solvent effects on tautomeric equilibria of 2‐pyridone/2‐hydroxypyridine 4‐pyridone/4‐hydroxypyridine in gas phase solution. The were investigated by self‐consistent reaction field (SCRF) theory implemented AMPAC MOPAC program two different ways: one which all relaxation is included quantum mechanics total energy must be corrected change energy, method A; a second directly includes this term, B. calculated (AM1, A)...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuantitative predictions of tautomeric equilibria for 2-, 3-, and 4-substituted pyridines in both the gas phase aqueous solution: combination AM1 with reaction field theoryMati M. Karelson, Alan R. Katritzky, Miroslaw Szafran, Michael C. ZernerCite this: J. Org. Chem. 1989, 54, 26, 6030–6034Publication Date (Print):December 1, 1989Publication History Published online1 May 2002Published inissue 1 December...

Abstract A rather complete data set for 12 characteristics of 18 common benzo‐fused heterocycles yields two significant principal components. The loadings the show a close correlation with those found same monocyclic heterocycles. scores each bicycle are also closely related to corresponding monocycle. method demonstrates considerable predictive power.

Abstract Restudy of an almost complete data set 12 characteristics for 16 common heterocycles confirms the previous conclusion [1] independence „classical”︁ and „magnetic”︁ aromaticity. The scores individual correlate well with their chemical structure.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInfrared intensities as a quantitative measure of intramolecular interactions. XIII. Molecular orbital calculations the ring-stretching bands substituted benzenesR. T. C. Brownlee, Alan R. Katritzky, M. V. Sinnott, Miroslaw Szafran, D. Topsom, and L. N. YakhontovCite this: J. Am. Chem. Soc. 1970, 92, 23, 6850–6855Publication Date (Print):November 1, 1970Publication History Published online1 May 2002Published inissue 1 November...

Conformations of flexible zwitterionic ω-pyridinium alkanoates (PBn) with n methylene units in the tether and their hydrates hydrochlorides are studied solid state by X-ray diffraction, aqueous solution FT-IR 1H,13C, 14N NMR spectroscopies, gas phase PM3, SAM1, DFT calculations. PB1 PB1·H2O crystals have a conformation N+···O intramolecular distance ca. 2.7 Å, while PB3·2H2O PB10·3H2O trans-zigzag arranged antiparallel. Structures isolated molecules dihydrates (PBn·2H2O) (PBn·HCl) optimized...

The tautomeric equilibrium constants of nine oxo and hydroxy derivatives five-membered heterocycles containing two ring heteroatoms (nitrogen or oxygen) as calculated by the AM1 quantum chemical model agree well with literature gas-phase data. inclusion solvent effects through a self-consistent reaction field technique into these calculations yields results in full agreement experimental data obtained for systems aqueous solution. It is not possible to use energies isolated molecules predict...

The preparation is reported of all four the monoalkyl derivatives 2-thiouracil and six possible dialkyl required as models for a study tautomeric equilibria by physical methods. Gas-phase proton affinities are determined using ion cyclotron resonance mass spectrometry, used to provide quantitative estimates individual tautomer stabilities in vapour state. These results agree well with qualitative deductions predominant structures from i.r. spectroscopy.

Abstract We examine solvent effects on carbon radical and ionic centers of HCXY by including a self‐consistent reaction‐field into the AM 1 MNDO electronic structure models to mimic dielectric effects. find that such concepts as merostability are principally effects, that, expected, molecules with large dipoles or charge assymmetry stabilized more than those atoms electrically neutral. Of some importance in this study is finding conformation also dependent solvation change geometry must be...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAb initio and semiempirical calculations on the tautomeric equilibria of N-unsubstituted N-substituted benzotriazolesAlan R. Katritzky, Konstantina Yannakopoulou, Ernst Anders, John Stevens, Miroslaw SzafranCite this: J. Org. Chem. 1990, 55, 22, 5683–5687Publication Date (Print):October 1, 1990Publication History Published online1 May 2002Published inissue 1 October...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChlorine-35 nuclear quadrupole resonance and infrared spectroscopic studies of hydrogen bonding in complexes dichloroacetic acid with nitrogen oxygen bases: correlation properties proton affinity aqueous pKaBoleslaw. Nogaj, Ewa. Dulewicz, Bogumil. Brycki, A. Hrynio, Piotr. Barczynski, Zofia. Dega-Szafran, Miroslaw. Szafran, Koziol, Alan R. KatritzkyCite this: J. Phys. Chem. 1990, 94, 4, 1279–1285Publication Date (Print):February 1, 1990Publication...

The crystal structure of the title compound has been determined by X-ray analysis. intramolecular hydrogen bond lengths are 2.606(3)Å for (NHN)+ bridge in protonated 1,8-bis(dimethylamino)naphthalene cation (DMAN+H) and 2.401(4)Å (OHO)– maleate anion (HM–). H-bonds asymmetrical not strictly linear: NHN, 157(3)° OHO, 170(5)°. geometries N—H⋯N O—H⋯C bridges investigated dominated spherical repulsions their constituent atoms.The overlapping bands absorbance IR spectra potassium (deuteron)...

Relative stabilities predicted by the AM1 method, and relative energies from 3-21 G* 6-31 G ** calculations agree with qualitative quantitative experimental vapour phase data for 2-thiouracil its four tautomeric monomethyl derivatives. The proton affinities more stable forms are usually significantly lower than, but almost within values of, measured PA values. A plot of vs. calculated gives a straight line unit slope.