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  • Articles  (15)
  • Physical Chemistry  (15)
  • Gas chromatography
  • Inorganic Chemistry
  • Wiley-Blackwell  (15)
  • 1995-1999  (15)
  • 1975-1979
  • Physics  (15)
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  • Articles  (15)
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  • Wiley-Blackwell  (15)
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  • 1
    Electronic Resource
    Electronic Resource
    Hyperbolic Model for the meta-para interrelationship in benzene derivatives (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 5-14 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new approach to the long-standing problem of interrelating meta and para substituent constants is presented. An analysis of the unified σ0-scale shows that the interrelation between σ40 and σ40/σ30 can be modelled by a pair of conjugate rectangular hyperbolae, one for normal (n) and the other for special (s) substituents. The latter are characterized by a lone electron pair in the first atom. The equations σ4n0 (σ4n0 - γ0)/(σ4n0 - 2γ0) = λ0 σ3n0 and σ4s0 = γ0 + λ0 σ3s0 are derived and discussed in terms of Taft's separation of mesomeric and non-mesomeric effects. Asymptotic values λ = 0.960 γ = -0.225 were obtained by non-linear least rectangles fitting. A nonnegligible mesomeric contribution to σ0 constants for normal substituents is predicted by the hyperbolic model. The present results are at variance with Exner's analysis of the meta-para interrelationship in benzene compounds with normal substituents. This divergence is ascribed to opposite views concerning the role of the π-inductive effect.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080104
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  • 2
    Electronic Resource
    Electronic Resource
    Structural study on quasi-phosphonium salts containing phosphorus-oxygen, phosphorus-oxygen, phosphorus-nitrogen and phosphorus-sulphur bonds (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 41-46 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal and molecular structues of six quasi-phosphonium salts containing phosphorus-heteroatom heteroatom=oxygen, sulphur or nitrogen0 bonds were determined. Comparison of the molecular parameters obtained with those available for reference structures demonstrated that the ‘double bond’ character for the P+ — Y bond decreases in the order Y = N ≫ O 〉 S.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080109
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  • 3
    Electronic Resource
    Electronic Resource
    Infrared study of the proton acceptor ability of metyrapone (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 77-83 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The hydrogen bond complexes between metyrapone [methyl-1,2-di(3-pyridyl)propan-1-one] and hydroxylic proton donors (phenols, water) were investigated by infrared spectroscopy. The thermodynamic and spectroscopic data determined in carbon tetrachloride suggest that the nitrogen atom of the pyridine ring A [bonded to the C(CH3)2 group] is the main hydrogen bond interaction site. The data are compared with di-2-pyridylglyoxal complexes where the hydrogen bonds are formed on the oxygen atom of the carbonyl function. In the solid adduct of metyrapone with HCl, protonation takes place on the two nitrogen atoms of the pyridine rings. The data from this work are compared with those from chemical oxidation, which leads predominantly to the formation of mono-N-oxide A and di-N-oxide.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080204
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  • 4
    Electronic Resource
    Electronic Resource
    Metal ion complexation by the phosphoryl and the carbonyl groups probed by 17O NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 605-609 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interactions between compounds containing phosphoryl, carbonyl, or hydroxyl groups (or combinations of these groups) with metal ions (Na+, Mg2+) were probed in CD3CN solutions by 17O NMR spectroscopy. For all phosphoryl and carbonyl substrates a strong high - field shift of the P=O and C=O signals was observed on the addition of a salt; no shift was observed, however, for the OH group signal, indicating that no chelation takes place in the hydroxyphosphoryl (or hydroxycarbonyl) derivatives. For 2-hydroxy-3-benzoylpropylphosphonic diester the 17O NMR studies, together with conformational analysis based on the 1H spectroscopy, demonstrated the chelation of a metal ion by the P=O and C=O functions (fermation of an eight-membered cyclic structure) with the OH group involved in the intramolecular hydrogen bonding, but not in the complexation to the metal ion.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080906
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  • 5
    Electronic Resource
    Electronic Resource
    Plurilinear improvement of the Hammett equation (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 671-688 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The original Hammett equation, Δ = ρσ, is transformed in a constrained tetralinear relationship where each straight line with variable intercept term correlates one of the following four groups or subsets of dipolar substituents: normal and special substituents (depending on the absence or the presence of a lone electron pair in their atom next to the aromatic ring) and, in each of these classes, separating meta and para derivatives. There are a total of four fitting parameters in the resulting plurilinear Hammettian transformation (PHT) from which the statistically corrected parameters λ and γ are derived; λ and γ are the asymptotic values in a hyperbolic model for the representation of Δ4 vs Δ4/Δ3. This meta-para interrelationship is assumed to hold in the absence of through-resonance effects which, in turn, are allowed for by the use of alternative sigma scales of substituent constants. By applying the PHT to a large number of selected literature data, parameters λ and γ are determined for the ionization equilibria of 3- and 4-monosubstituted benzoic acids, anilinium ions, phenols and pyridinium ions. In these reactions series, parameter λ, which measures the para/meta ratio of field/inductive effects, is lower than unity and shows a marked dependence on the basic molecular framework. It is best modelled in terms of a through-space field effect approach. The ratio γ/γ0, where γ0 is referred to the unified sigma-zero scale, is shown to correspond to the original Hammett's reaction constant ρ. It is concluded that the PHT constitutes an improved Hammett equation for the analysis of substituent effects in benzene derivatives taking into account statistical errors and making allowance for different transmission coefficients for the field/inductive effect from meta and para positions in different reaction series.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610081006
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  • 6
    Electronic Resource
    Electronic Resource
    Structure of the intermediate formed in the synthesis of symmetrical pyrylium ions (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 731-741 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of symmetrical blocked pyrylium derivatives by reaction of a cyclic aromatic ketone with ethyl orthoformate goes through an intermediate which can be isolated under certain conditions. This intermediate is unstable when starting from 1-tetralone derivatives but, surprisingly, it can be isolated easily when the synthesis is performed with 1-indanone derivatives. Further, in the latter case, this intermediate cyclizes hardly into the expected blocked pyrylium derivative. Its ionic structure was demonstrated by mass spectrometry and by 500 MHz 1H and 13C NMR techniques including heteronuclear H-C COSY and DEPT polarization transfer experiments. Hydrolysis of this intermediate in aqueous ethanol solution forms, in acidic or basic media, a pseudo-base, which in the latter case presents strong similarities with that obtained by the base-catalysed ring-opening of a blocked pyrylium ion. In both acidic and basic solutions, the pseudo-base obtained by the two sources shows identical UV-visible absorption spectra. The difficulty of the intermediate (g) originating from 1-indanone derivatives in cyclizing into the blocked pyrylium structure, in contrast to the intermediate formed from 1-tetralone derivatives, is tentatively explained.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610081106
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of reaction of acridine orange with bromateion at low pH (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 175-185 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction between acridine orange hydrochloride [3,6-bis(dimethylamino)acridine hydrochloride] and potassium bromate in dilute sulphuric acid was studied by monitoring the absorbance change at 492 nm. The reaction exhibited complex kinetic behaviour. In excess bromate the reaction had an induction period with slow depletion of acridine orange (AC) followed by a fast depletion step. The initial reaction step was found to be first order with respect to both AC and bromate and second order with respect to H+. The stoichiometric ratio of AC to bromate was 3 : 2. At the end of the induction period, the redox potential of the reaction mixture has shown a distinct rise, while the Br- concentration dropped sharply. The dual role of bromide ion both as an inhibitor and autocatalyst is discussed. A 16-step reaction mechanism is proposed and the simulated curves agreed well with the kinetic curves.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080308
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  • 8
    Electronic Resource
    Electronic Resource
    Solution electron affinity changes via the deuteriation of the methyl groups of p-xylene (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 371-376 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: EPR techniques, including spectral double integration, were utilized to measure the equilibrium contants in dimethoxyethane at 195 K for electron transfer between perdeuteriated p-xylene and xylene, α-d3-p-xylene and α,α′-d6-p-xylene. The results, coupled with the law of Hess, yield all the relative solution electron affinities (EA). It was found that methyl deuteriation lowers the solution EA by 160 J l mol-1 per deuterium, whereas ring deuteriation in these systems lowers the solution EA by about 370 J l mol-1 per deuterium, which is about the same effect as is observed in the benzene system. The results are discussed in terms of hyperconjugative, inductive and solvation effects.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080510
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of the empirical polarity parameter ET(30) for binary solvent mixturesSee Ref. 1. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 617-625 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Empirical solvent polarity parameters ET(30) were determined by UV-visible spectrophotometry using Dimroth- Reichardt's betaine dye, as a function of composition, for (aprotic + aprotic) and (aprotic + protic) binary solvent mixtures. For (aprotic + aprotic) solvent systems the cosolvent was toluene, and the other solvents used were selected with different structural characteristics and an extensive range of polarity: chloroform, 1,4-dioxane, ethyl acetate, tetrahydrofuran, acetone, nitromethane and N,N-dimethylformamide. For (aprotic + protic) solvent systems, the protic cosolvent used was methanol, and the aprotic solvents selected were toluene, chloroform, 1,1,1-trichloroethane, tetrahydrofuran, acetone, N,N-dimethylformamide, and dimethyl sulphoxide. Each system was analysed according to its deviations from additivity due to selective solvation of the betaine. A preliminary application of these empirical solvent polarity parameters was related to the solvent effects in a simple example of a nucleophilic aromatic substitution reaction.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080908
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  • 10
    Electronic Resource
    Electronic Resource
    Structure and conformation of (3S*, 4S*, 6R*)- and (3R*, 4R*, 6R*)-3,6-dimethyl-4-phenylsulphonyltetrahydropyran-2-ones (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 747-752 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The nucleophilic ring opening of propylene oxide by the lithio derivative of the trioxabicyclic orthoester 1 leads, after acidic treatment, to the title lactones 3a and 3b with no evidence of δ-lactones 3c and 3d. The stereochemistry of these two lactones has been established by X-ray diffraction analysis. The ring conformations observed in the solid phase are similar in both lactones and are compared with those observed in related molecules. However, the NMR spectroscopic analysis shows that this similarity does not exist in solution; lactone 3a adopts a different conformation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610081108
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