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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogen-bonding. Part 4. An analysis of solute hydrogen-bond basicity, in terms of complexation constants (log K), using F1 and F2 factors, the principal components of different kinds of basicityPart 3. M. H. Abraham, P. P. Duce, D. V. Prior, R. A. Schulz, J. J. Morris and P. J. Taylor, J. Chem. Soc. Faraday Trans. 1, 84, 865 (1988). (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 243-254 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The principal components factors F1 and F2 in the equation \documentclass{article}\pagestyle{empty}\begin{document}$$ \log K = {\rm BDP}_0 + S_1 F_1 + S_2 F_2 $$\end{document} have been used to obtain S1 and S2 values for sets of hydrogen-bond bases against 32 reference acid/solvent systems. The constants S1 and S2 define an angle θ = tan-1 S2/S1 that is a measure of the electrostatic:covalent bonding ratio in the hydrogen-bond complex. It is shown that θ can vary from 53 (4-fluorophenol in CH2Cl2)to 86 degrees (Ph2NH in CCl4) depending on the reference acid and solvent. This variation in θ can lead to family dependent behaviour in plots of log K for bases against a given reference acid system vs log K for bases against another reference acid system, and precludes the construction of any general scale of hydrogen-bond basicity using log K values. Amongst a quite wide range of reference acid/solvent systems θ varies only from 64 to 73 degrees, and for bases against these reference systems a ‘reasonably general’ scale could be set up. Such a scale could be extended to bases against reference acid/solvent systems outside the 64-73 degree range provided that certain classes of base (e.g. pyridines, alkylamines) were excluded from the additional reference acid/solvent systems.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610020307
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  • 2
    Electronic Resource
    Electronic Resource
    Model solvent systems for QSAR. Part IV. The hydrogen bond acceptor behaviour of heterocycles (1994)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 743-750 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An LSER analysis based on the partitioning of 15 proton acceptor heterocycles has succeeded in extracting Σβ values, but only at the cost of demonstrating solvent dependence for some of them. As noted by Abraham, the division lies between protic and aprotic organic phases. His observation that pyridine and quinoline are less effective acceptors when surrounded by solvent than in 1 : 1 association was confirmed, and possible reasons for this are discussed. Two other such cases are N-methylimidazole and pyridazine, both of which give lower Σβ values in octanol than in PGDP. For both, Σβ in PGDP is what would be expected on the basis of log Kβ. The value for pyridazine in octanol suggests that, here, the ‘α-effect’ is no longer operative; it is possible that this result can be generalized to other such heterocycles. Elsewhere, the most remarkable finding is that, where there are two proton acceptor sites in one heterocyclic ring, Σβ is the simple unattenuated sum of the separate βf values. If this result is general, it leads to a very simple way of estimating Σβ for heterocycles by calculation where data are unavailable. Evidence was also found, in certain cases, for hydrogen bonding to the π-donor heteroatom or the aromatic ring. The QSAR implications of these results are discussed.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610071213
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  • 3
    Electronic Resource
    Electronic Resource
    Electrochemical and photoelectronic spectral study of compounds with high ionization potentials: Anodic oxidation of vinyl triflates in aprotic solvents (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 670-676 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microelectrodes can be used to measure redox half-wave potentials in aprotic solvents containing no purposely added supporting electrolyte. By employing an electrode of sufficiently small size, the accessible potential range in solution is considerably extended. The electrochemical oxidation of vinyl (enol) triflates, which are oxidized at high electrode potentials, can therefore be studied using an ultramicroelectrode. Oxidation and ionization potentials, determined by ultramicroelectrode voltammetry and He I photoelectron spectroscopy, respectively, of 2-methylprop-1-enyl, cyclohexenyl, cyclopentenyl, 1,1-diphenylethenyl and prop-2-enyl triflate are reported. The results from electrochemical measurements and photoelectron spectra were compared.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031008
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  • 4
    Electronic Resource
    Electronic Resource
    Hydrogen-bonding 8.Part 7; M. H. Abraham, P. L. Grellier, D. V. Prior, P. P. Duce, J. J. Morris and P. J. Taylor. J. Chem Soc., Perkin Trans. 2, (in press). Possible equivalence of solute and solvent scales of hydrogen-bond basicity of non-associated compounds (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 540-552 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Using the solvatochromic indicator method, a scale of solvent hydrogen-bond basicity, β1 (General), has been set up using a series of double regression equations, \documentclass{article}\pagestyle{empty}\begin{document}$$ \nu = \nu _0 + s\pi _1^* + b\beta _1 $$\end{document} for 11 aniline-type indicators. A similar solvent scale, β1 (Special), has been constructed by the homomorphic comparison method using only results by Laurence et al. on the indicators 4-nitroaniline and 4-nitro-N,N-dimethylaniline. Results are available from our previous work on a general solute scale, β2H, and we have also obtained a special solute scale, β2 (pKHB) from available log K values for hydrogen-bond complexation of bases with 4-fluorophenol in CCl4. However, the two solute β2 scales are virtually identical.It is shown that there is a general connection between β1(General) and β2H, with r = 0·9775 and s.d. = 0·05 for 32 compounds, and between β1(Special) and β2H, with r = 0·9776 and s.d. = 0·06 for the same 32 compounds. The latter correlation over 60 compounds yields r = 0·9684 and s.d. = 0·07. However, there are so many compounds in these regressions for which the differences in the solvent and solute β values are larger than the total expected error of 0·07 units that the use of β1 to predict β2 or vice versa is a very hazardous procedure. About 70 new β1 values obtained by the double regression method are also reported.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610020706
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  • 5
    Electronic Resource
    Electronic Resource
    Thermodynamic and kinetic analysis of the dimerization of aqueous glyoxal (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 18 (1986), S. 775-789 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Equilibria and rates of interconversion between monomeric and dimeric glyoxal were measured in aqueous solution. The equilibrium constant [G2]/[G1]2 was 0.56 M-1 at 25°C, and was hardly affected by changes of ionic strength and pH but increased rapidly with increase of temperature. The rate of depolymerization was first-order in dimer, with the pseudo first-order rate coefficient in the pH range 1.3-7.8being of the form b1[H3O+] + b2 + b3[OH-]/(1 + b4[OH-]) + b5[OH-]. Coefficients b1 and b2 were more strongly affected by changes of temperature, though [OH-] was much the more effective catalyst. This rate form has not previously been observed for monomer-dimer inter-conversion of α-hydroxycarbonyls and α-dicarbonyls or for related reactions such as mutarotations and hydrations. Equivalent rate forms arisefrom reactions where an intermediate at steady state and low concentration is produced.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550180705
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetics of the thermal gas-phase dimerization of hexafluoropropene (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 537-546 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reversible thermal gas-phase dimerization of hexafluoropropene to the four isomeric cyclobutanes has been studied by pressure change and by gas-liquid chromatographic analysis in the temperature range of 645-708 K with initial pressures of olefin from 802 to 4820 mm Hg. The reaction was accurately second order at low conversions of olefin to dimers, and at higher conversions it gave a very good fit to the rate equation for opposing second- and first-order reactions. The rate constants for the dimerization, calculated from initial rates of reaction, yielded the least-mean-squares Arrhenius equation (95% confidence limits): \documentclass{article}\pagestyle{empty}\begin{document}$$ \log _{10} (k_2 /{\rm dm}^3 {\rm mol}^{ - 1} s^{ - 1}) = (5.93 \pm 0.40) - (131.8 \pm 9.5)k{\rm J\,\,mol}^{{\rm - 1}}/RT\ln \,10 $$\end{document} where k2 is defined by \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{ - 1/2{\rm d}[{\rm C}_3 {\rm F}_6]}}{{dt}} = \frac{{{\rm d}[c - {\rm C}_6 {\rm F}_{12}]}}{{dt}} = k_2 [{\rm C}_3 {\rm F}_6]^2 $$\end{document} Studies carried out in a packed vessel showed no evidence of heterogeneity. The rate constants found in this work are in excellent agreement with those found at lower pressures by Atkinson and Tsiamis, and the combined results give the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ \log _{10} (k_2 /{\rm dm}^{\rm 3} {\rm mol}^{{\rm - 1}} {\rm s}^{{\rm - 1}}) = (6.47 \pm 0.21) - (138.6 \pm 2.7){\rm kJ\,mol}^{{\rm - 1}} {\rm /}RT\ln 10 $$\end{document}
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150604
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the aquation of pentaaqua (trichloroacetato-O)-chromium(2+) ion (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 13 (1981), S. 1203-1213 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the aquation of (H2O)5Cr(O2CCCl3)2+ have been examined at 35-55°C and 1.00M ionic strength with [H+] = 0.01-1.00M. The reaction follows the rate equation -d ln [Crtotal]/dt = (a[H+]-1 + b + c[H+])/(1 + d[H+]), where [Crtotal] is the stoichiometric concentration of the complex. At 45°C a = (1.41 ± 0.03) × 10-7M/s, b = (1.66 ± 0.02) × 10-5 s-1, c = (7.0 ± 0.8) × 10-5M-1·S-1 and d = 2.3 ± 0.3M-1. Two mechanisms consistent with this rate law are discussed, with evidence being presented in favor of an ester hydrolysis mechanism involving steady-state intermediates. Equilibrium and activation parameters were determined.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550131110
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic analysis of the disproportionation of aqueous glyoxal (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 18 (1986), S. 757-773 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rates of disproportionation of 0.015-0.4 mM aqueous glyoxal toglycolic acid were measured at 0.24-75 mM NaOH and constant ionic strength, leading to the empirical rate expression r = (a1[OH-] + a2[OH-]2) [GT]/(1 + a3[OH-]), where [GT] is the total glyoxal concentration. These results were confirmed in bicarbonate/carbonate buffer and at 2-20 mM [GT]. The rate form is in contradiction to earlier work on glyoxal, which suggested a second-order dependence on [OH-], but agrees with the rate equation for phenylglyoxal disproportionation. The kinetic data can be explained by a mechanism postulating the presence of monohydrated and dihydrated forms of glyoxal in equilibrium, with the rate-limiting steps being intramolecular hydride ion transfers to the unhydrated carbonyl carbon of the mono- and divalent anions of glyoxal monohydrate.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550180704
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