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  • Articles  (10)
  • Articles: DFG German National Licenses  (10)
  • Physics  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Cross interaction constants as a measure of the transition state structure (part III). Mechanism of reactions between 1-phenylethyl benzenesulfonates with N,N-dimethylanilines (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 35-42 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics and mechanisms of the reactions between 1-phenylethyl benzenesulfonates (1-PEB) with N,N-dimethylanilines are investigated in methanol at 35·0°C. Reactivity and selectivity trends were found to be similar to those for the reactions of 1-PEB with anilines, but the magnitudes of cross interaction constants, ρXZ, between substituents X in the nucleophile and Z in the leaving group were substantially smaller indicating no hydrogen-bond bypass bridge formation in the transition state. However, the magnitude of ρXZ suggested a direct electrostatic interaction between the reaction centers in the nucleophile and leaving group in the frontside nucleophilic attack with a loose transition state structure.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610020105
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  • 2
    Electronic Resource
    Electronic Resource
    Cross-interaction constants as a measure of the transition state structure. Part 8. Mechanism of the reaction of 2-phenylethyl benzenesulphonates with benzylamine in acetonitrile (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 545-549 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of reactions between 2-phenylethyl benzenesulphonates (2-PEB) and benzylamines in acetonitrile at 65·0°C have been studied; the mechanism was examined on the basis of the sign and magnitude of cross-interaction constants ρij and βij. In contrast to the reactions of 2-PEB with anilines in methanol, participation of the aryl-assisted pathway was negligible, with a strong indication that the reaction proceeds largely by an intermolecular SNi mechanism with a four-centre transition state (TS). The effect of substituents on the TS variation was in accord with the predictions of the quantum mechanical model.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030808
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  • 3
    Electronic Resource
    Electronic Resource
    Nucleophilic substitution reaction of benzyl bromide with N, N-Dimethylaniline: Significance of equilibrium cross-interaction constant (1994)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 555-560 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Kinetic studies on the reversible reactions of benzyl bromides with N, N-dimethylanilines were carried out for both the forward (kf) and reverse (kr) directions. The equilibrium constants, K were calculated using the ratio kf/kr and the equilibrium cross-interaction constant, ρeXY was determined. The ρeXY value was shown to represent a maximum intensity of interactions between substituents X and Y through covalent bonds within a molecule. The normalized values of ρX (ρnuc) and ρXY indicate that in the transition state the fractional development or loss of polar and resonance interactions in the benzyl system are imbalanced or non-perfectly synchronized. In the forward reaction the fractional loss of resonance interaction becomes enhanced, whereas in the reverse reaction the fractional development of resonance interaction lags behind the corresponding changes of polar interactions by ca 45%.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610071006
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  • 4
    Electronic Resource
    Electronic Resource
    Cross-interaction constants as a measure of the transition state structure. Part 9. The degree of bond formation in the SN2 transition state involving anionic nucleophiles (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 550-554 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The second-order rate constants of the reactions between benzenesulphonyl chlorides and anionic nucleophiles, benzoates and cinnamates, in methanol at 30·0°C are reported. A marked increase in rate found with a p-nitro substituent in the substrate indicated the development of an electron-rich centre on the S atom in the transition state. The two types of cross-interaction constants, ρxy and λxy, suggested that bond formation in the SN2 transition state with anionic nucleophiles is greater than that for the corresponding reaction with aniline nucleophiles.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030809
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  • 5
    Electronic Resource
    Electronic Resource
    Cross interaction constants as a measure of the transition state structure. 13. Steric effects of the N,N-dimethyl group on the transition state structure in aminolysis of alkyl benzenesulphonates (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 751-756 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Kinetic studies on the reactions of methyl (MBS) and ethyl benzenesulphonates (EBS) with N,N-dimethylanilines (DMA) in methanol and acetonitrile are reported. The cross interaction constants ρXZ and βXZ, between the substituents in the nucleophile (X) and the leaving group (Z) indicated that the transition states (TS) are looser than those for the reactions with anilines, but the relative tightness between the two substrates was the same; the TS was tighter for EBS despite the increase in steric effect leading to looser TSs for MBS and EBS alike. The TS variation between two different reaction series expected from the simple Hammett and Brønsted coefficients, ρX, ρZ, βX and βZ, was incompatible with that predicted by the cross interaction constants, demonstrating again the unreliability of the simple parameters.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031109
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  • 6
    Electronic Resource
    Electronic Resource
    Cross-interaction constants as a measure of the transition state structure (part V).For Part IV, see ref. 3. The transistion state structure for reactions of phenacyl benzenesulphonates with benzylamines in methanol (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 484-490 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Kinetics of reactions of phenacyl benzenesulphonates with benzylamines were investigated in methanol at 45·0 °C and the cross-interaction constants λXY, λYZ and βXZ were determined in order to elucidate the transition-state structure. The unusually small magnitude of λXY can only be accounted for by the resonance ‘shunt’ effect of the α-CO group of the phenacyl system. Large |λYZ| values indicate a small degree of bond breaking whereas relatively large |βXZ| values compared with those for the dissociative SN2 reaction indicate a relatively tight transition state for the reactions. Further, the similar magnitudes of βXZ values compared with those of the corresponding aniline nucleophile series suggest a similar transition-state structure for the two armatic amine nucleophile series.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610020607
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  • 7
    Electronic Resource
    Electronic Resource
    Cross-interaction constants as a measure of the transition state structure. Part 15. Kinetic isotope effects in the SN2 reactions of 2-phenylethyl derivatives with deuterated aniline nucleophiles (1991)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 4 (1991), S. 101-106 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Kinetic isotope effects (KIE) were determined for the reactions of 2-phenylethyl and 1-methyl-2-phenylethyl benzenesulphonates with deuterated aniline nucleophiles in acetonitrile at 65.0 °C. The results are in good agreement with the transition state (TS) structures proposed based on the sign and magnitude of the cross-interaction constants, pxz, between the substituents in the nucleophile (X) and the leaving group (Z). In the reactions of 2-phenylethyl derivatives, all three reaction pathways, kr, kt and kΔ, were found to be contributing competitively; the inverse secondary KIE observed with a stronger nucleophile changed into the primary KIE with a weaker nucleophile owing to the predominant contribution of the four-centre TS in the kf path. For the reactions of the 1-methyl-2-phenylethyl series, the kr path played a major role, the contribution from the front-side nucleophilic attack, kf, being negligible. In both reaction series, the aryl participation was important for the p-CH3O-substituted substrate.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610040206
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic solvent isotope effect studies on the methanolysis of 1-phenylethyl chlorides (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 361-366 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The negative slope (ΔρY+ 〈 0) of the Hammett-type plot using kinetic solvent isotope effect, log kSOH/kSOD versus σ+, for methanolysis of 1-(Y-phenyl)ethyl chlorides is rationalized by an ion-pair mechanism in which a solvent molecule attacks the relatively stable carbocation formed in the pre-equilibrium.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060608
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  • 9
    Electronic Resource
    Electronic Resource
    Theoretical studies on the transition-state imbalance in malononitrile anion-forming reactions in the gas phase and in water (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 908-916 
    Details
    ISSN: 0894-3230
    Keywords: AM1-SM2.1 ; transition-state imbalance ; benzylidenemalonotriles ; nucleophilic additions ; Brønsted coefficients ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---Semiempirical MO theoretical studies were carried out on the nucleophilic addition of phenoxide nucleophiles to 1,1-dicyano-2-arylethenes in the gas phase and in water using the AM1 method and the Cramer-Truhlar solvation model SM2.1. The gas-phase αn and βn values are 0·81 and 0·65, respectively, leading to the positive imbalance of I=0·16; the electric polarization and dispersion interactions of water incorporated in the SM2.1 model reduce both the αn and βn values to 0·61 and 0·36, giving I=0·25. The two Brønsted coefficients obtained theoretically in water agree satisfactorily with the experimental values (αncorr=0·55 and βn=0·35) obtained with amine bases. The small imbalance found both theoretically (I=0·25) and experimentally (I≈0·20) can be ascribed to (i) a near-zero distance factor, Δd=dp-dTS≈0 and (ii) the small extent of negative charge localization by strucutral reorganization in the transition state. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the aminolysis of p-nitrophenyl N-phenylcarbamates (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 725-730 
    Details
    ISSN: 0894-3230
    Keywords: p-nitrophenyl N-phenylcarbamates ; stepwise mechanism ; rate-limiting breakdown of T± ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---Kinetic studies of the reactions of p-nitrophenyl N-phenylcarbamates with benzylamines were carried out in acetonitrile at 25·0 °C. Second-order (k2) and third-order (k3) rate constants were observed for all the Y-substituted carbamates except for Y=m-Cl. The relatively large magnitude of ρX (for X-substituted benzylamines) and ρY together with a positive cross-interaction constant ρXY supports a stepwise mechanism involving rate-limiting breakdown of the zwitterionic tetrahedral intermediate T±. Kinetic isotope effect studies with deuterated benzylamine (XC6H4CH2ND2) indicate that in the base-catalyzed path, k3, rate-limiting deprotonation occurs at the amino group of benzylamine within the T± intermediate. The low δH≠ and δS≠ values for the k3 process are in accord with the proposed mechanism © 1997 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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