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  • 1990-1994  (879)
  • 1925-1929
  • 1993  (879)
  • Engineering  (661)
  • Physical Chemistry  (218)
  • 1
    Electronic Resource
    Electronic Resource
    Introducing engineering into American secondary education (1993)
    Springer
    Journal of science education and technology 2 (1993), S. 397-406 
    Details
    ISSN: 1573-1839
    Keywords: Engineering ; technological literacy ; hands-on experiments ; active learning ; content instruction ; videotaping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract Media reports indicate the decline of the technological literacy of American youth, especially that students in other countries are better prepared in science and mathematics. Our active-learning program, which consists of numerous hands-on experiments, introduces engineering applications into science and math programs, that will demonstrate to students the usefulness of the theory that they currently do not see as useful. The program, when fully developed, will make optimum use of technology, especially computers and videotapes. The hands-on experiments allow students to discover fundamental principles through data analysis and then use the principles to synthesize a solution to a technological problem. This discovery-based education will help school systems better meet performance standards such as those in the Maryland School Performance Plan. The experimental approach to science education is especially important in a technology-oriented economy where children use the new technologies without understanding the principles on which they are based.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694528
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  • 2
    Electronic Resource
    Electronic Resource
    Concurrent boundary element computation (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 83-98 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A major limitation of the boundary element method (BEM) for the solution of electrical potential problems is the long computational time required. However, a large portion of the calculations involved can be viewed as being parallel in nature and can therefore be computed concurrently. This paper makes an effort to increase the efficiency of the BEM process using transputer-based multiprocessor computing techniques. The algorithms developed may equally well be applied to any multiprocessor system. The application selected to demonstrate the technique is the solution of an electrostatic problem governed by a two-dimensional Laplace equation.A parallel algorithm for problem setup and field extraction using BEM is designed and implemented on a transputer array. Special attention is directed to the utilization of the parallel processors to achieve maximum efficiency. The analysis in this work concentrates on the communication strategies for passing data between processors as well as a consideration of the workload attributed to each processor.The parallel algorithms were implemented using 3L Parallel Fortran; however, the choice of topology for the overall BEM implementation was limited by the fact that certain parts of the algorithm could only utilize a pipeline configuration of processors. Comprehensive results for the parallel BEM algorithm are given and they are encouraging, indicating that parallel processing has much to offer when applied to the boundary element method.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060202
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  • 3
    Electronic Resource
    Electronic Resource
    The efficiency of transmission-line matrix modelling - a rigorous viewpoint (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 109-126 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The difference equations of the scalar linear transmission-line matrix (TLM) routine as introduced by Johns for numerically solving the diffusion equation are shown to be isomorphic to Goldstein's correlated random walk model of diffusion. For the infinite homogeneous bar their exact solution is derived algebraically and given in the form of Jacobi polynomials. This puts the TLM algorithm on a sounder mathematical and physical basis. The accuracy in solving the diffusion equation is investigated in general form and thus its astonishing efficiency explained. Several other basic questions of this numerical technique are also discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060204
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  • 4
    Electronic Resource
    Electronic Resource
    Electronic band structure for two-dimensional periodic lattice quantum configurations by the finite element method (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 283-297 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A finite element method formulation is given for solving Schrodinger's wave equation for a single electron in a crystal lattice cell subject to a known periodic potential. The formulation has been implemented for a two-dimensional lattice, with an arbitrary potential profile, modelled by quadratic isoparametric elements, The FEM solver returns a specified number of electronic energy states, En, and nodal values of the complex wavefunctionψn Input data is generated by a standard FEM mesh generator. The postprocessing, given n, for reproducing a full 2-D E-k Brillouin diagram and given k, the electronic distribution, has been implemented. Tests on a 2-D generalized Kronig-Penney energy band model showed excellent agreement; between FEM results and analysis. The solver was further satisfactorily checked against published augmented plane wave calculations for a circular potential well within a square lattice. Specimen results are presented for the same circular well but with graded potential distributions and for a rectangular potential barrier set askew in a square lattice. Two-dimensional energy band solvers have application to superlattice nanostruc- tures, whilst a general, full 3-D FEM quantum solver seems feasible.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060405
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  • 5
    Electronic Resource
    Electronic Resource
    An E-plane sectoral horn fitted with side-lobe suppression devices (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 145-159 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A finite difference method is used to design a new type of sectoral horn antenna with corner channel inserts which produces a tapered aperture amplitude distribution in the E-plane. The channel inserts, which present a simple modification to the horn aperture geometry, act as effective side-lobe suppression devices. The efficiency of the suppression technique was successfully tested on an experimental horn whose performance is compared to that of a horn with similar geometrical dimensions but with no channel sections.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060207
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  • 6
    Electronic Resource
    Electronic Resource
    Body fitted grid generation with moving boundary and its application for dielectric waveguides (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 127-134 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The stress birefringence and mode coupling effects in polarization-preserving fibres are most important problems which need to be improved. For a realization of some optical devices, the dielectric waveguide with sinusoidally varying circular cross-section has been investigated. It becomes very important to analyse the electromagnetic field distribution in a dielectric waveguide with a time-dependent moving boundary. This paper shows that numerical methods can simulate the effect of the external disturbance on the dielectric waveguide from time to time. The author has discussed body fitted grid generation with moving boundary for the Poisson and Laplace equations.1,2 We have extended this technique for Maxwell's equation. The technique employs a kind of an expanded numerical grid generation. As the author adds the time component to grid generation, the time dependent co-ordinate system which coincides with a contour of moving boundary can be transformed into a fixed rectangular co-ordinate system. We could show the electric distribution in the waveguide time by time to verify the possibility of an application for an optical fibre. This technique makes it possible not only to analyse the effect of the external disturbance in a coherent optical communication system but also to fabricate optical devices.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060205
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  • 7
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060301
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  • 8
    Electronic Resource
    Electronic Resource
    Consistent finite difference modelling of Maxwell's equations with lossy symmetrical condensed TLM node (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 207-220 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A propagator integral interpretation for general TLM processes is presented and applied to discretized Maxwell's equations. The approach provides exact algebraic solutions of finite difference equations along a quite universal scheme.Specifically, Johns's process based on the symmetrical condensed node is reconstructed and generalized as a clear-cut FD algorithm. The fields computed are exact time-domain solutions of the FD equations, provided that total voltages and currents are evaluated and stub quantities are not externally excited. Losses are very naturally incorporated into the TLM algorithm.The structural similarity of the TLM process (properly operated) with the propagator integral appears just as fundamental as general and should have further applications.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060305
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  • 9
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060101
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  • 10
    Electronic Resource
    Electronic Resource
    Efficient analytical-numerical modelling of ultra-wideband pulsed plane wave scattering (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 3-17 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Ultra-wideband (UWB) pulsed plane wave scattering from a large but finite strip grating in free space is analysed in the frequency domain via decomposition into plane wave spectra, implemented numerically by the method of moments, and then inverted into the time domain (TD). To make this procedure practical under UWB conditions, closed form expressions are derived for interaction integrals involving widely separated expansion and testing functions. These closed forms are based on a judicious choice of the basis functions, and on asymptotic methods for reducing the integrals. Although large separation distances are assumed, the expressions have been found to be accurate for separations as small as 0·1 wavelengths. The TD self terms can also be evaluated efficiently. To test the frequency domain algorithm, comparisons are made with available data in the literature for surface currents and far-field scattering from multiple strips. New short pulse TD results are shown as well.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060103
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  • 11
    Electronic Resource
    Electronic Resource
    Spatially weighted numerical models for the two-dimensional wave equation: FD algorithm and synthesis of the equivalent TLM model (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 47-65 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper a new TLM model for the two-dimensional wave equation is introduced. It is synthesized directly from a FD algorithm. The FD algorithm is second-order-accurate in both space and time, and is explicitly time-stepped. The spatial derivatives in the FD algorithm are approximated by the weighted combination of two standard central difference stencils, one oriented as usual, the other rotated by 45° with its arms extended by a factor of (2)1/2. The TLM model is realized as the weighted connection of two original models (with the same geometrical configuration as the FD algorithm). The weighting in the TLM model is accomplished by using a variable intrinsic impedance for specific elemental transmission lines. The FD and TLM methods possess identical dispersion relations if the former is operated at its upper limit of stability. Therefore, under these conditions both represent identical models for the simulation of wave propagation. The propagation characteristics of the new model are investigated and the conditions for approximate numerical isotropy are provided. The numerical implementation (scattering matrix and transfer event) is described. To validate the new model, the calculation of cutoff frequencies of various modes in rectangular waveguide is performed. Comparison with analytical results (for an unfilled waveguide) and other numerical results (for a waveguide partially filled with a dielectric) validate the implementation of the model.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060106
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  • 12
    Electronic Resource
    Electronic Resource
    Redundancy and its implications in TLM diffusion models (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 135-144 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Redundancy in the simplest form of a two-dimensional TLM network is identified and a method of eliminating it is described. Results obtained using the non-redundant algorithm are compared with those derived from the standard, redundant algorithm. The non-redundant approach is extended to deal with non-uniform elemental capacitance; a cylindrical geometry is taken as an example of this. The scope for and benefits of rendering TLM diffusion models non-redundant are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060206
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  • 13
    Electronic Resource
    Electronic Resource
    Thermal radiative boundaries in TLM (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 165-166 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060209
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  • 14
    Electronic Resource
    Electronic Resource
    Boundary element estimation of current density distribution and eddy current loss in bundled multi-wire cables (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 169-181 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A numerical approach to the estimation of the current density distribution and the eddy current loss in bundled multi-wire cables using the boundary element method is proposed. Under the assumption of the gradual twist of the bundled wires, the cables are modelled to be two-dimensional with respect to their cross-sections. Three-phase transmission lines of cyclic symmetrical configuration are considered for which a reduction method is utilized to provide efficient computation. Some numerical demonstrations are made for three types of three-phase transmission-line models, consisting of a single wire and three and seven bundled wires. Two cases are considered: one in which the bundled wires are electrically contacted one to another on their surfaces and one in which they are independently insulated. The equivalent resistance is also calculated to examine the skin effect. The skin effect and the effectiveness of the multi-wire configuration to reduce the skin effect are well demonstrated.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060302
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  • 15
    Electronic Resource
    Electronic Resource
    An investigation of the different TLM configurations used in the modelling of diffusion problems (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 253-268 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The commonly used transmission-line modelling (TLM) network of one-dimensional diffusion problems often results in unwanted oscillations. Two different TLM configurations (line boundary (LB) and resistance boundary (RB)), are investigated with some techniques necessary to reduce the oscillations. Comparisons between the various LB and RB models addressed in this paper, indicate that, in general, two-dimensional TLM models produce consistently more accurate results.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060403
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  • 16
    Electronic Resource
    Electronic Resource
    The analytical and numerical solution of electric and magnetic fields, K. J. Binns, P. J. Lawrenson and C. W. Trowbridge, Wiley, New York 1992. Price: US$ 79.95 (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 305-307 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060407
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  • 17
    Electronic Resource
    Electronic Resource
    Study of initial- and transition-state solvation in the solvolysis of tert-butyl halides in alcohols from infinite dilution activity coefficients (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 133-138 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Gibbs energies of activation of the solvolytic reactions of tert-butyl halides (chloride, bromide and iodide) in eight mono-alcohols and eight di-alcohols were dissected into contributions from the initial state and transition state. The unified approach proposed by Abraham was applied and the various factors making up the overall solvent effect in both states were identified and compared. To perform this study, the Gibbs energies of transfer of the initial state were calculated using the infinite dilution activity coefficient values of the solutes in the solvents, γ∞. These values were determined from the UNIFAC group-contribution method, with the modified Flory-Huggins equation in the combinatorial term and with group interaction parameters from the Parameter Table exclusively based on experimental γ∞ data reported in the literature. It is concluded that solvent polarizability and polarity-HBD acidity and cavity effects during the activated process are mainly due to transition-state contributions.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060302
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  • 18
    Electronic Resource
    Electronic Resource
    [4] Metacyclophane: STO-3G molecular structure, strain energy and CNDO/S—Cl electronic transition energies (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 163-170 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular structure of [4] metacyclophane is optimized at the ab initio STO-3G SCF level and a genuine minimum is located. In the STO-3G structure the benzene ring is less bent and geometrically distorted than in the previously reported MNDO structure. Although some bond alternation is calculated for the carbon-carbon bond lengths of the bent benzene ring, their values still fall in the range of highly delocalized compounds. Despite the fact that the STO-3G strain energy [SE(tot.)] is larger than the corresponding MNDO strain energy, the distribution of SE(tot.) over the bent benzene ring [SE(bb.)] and the oligomethylene bridge [SE(br.)] is similar. To facilitate the hitherto unsuccesful identification of [4] metacyclophane, its electronic transition energies were calculated with CNDO/S-CI using the STO-3G geometry as input geometry. The reliability of the CNDO/S-CI results was assessed by a comparison of calculated and experimental electronic transition energies for p- and, m-xylene, [5] para- and [5] metacyclophane and [4] paracyclophane following the same approach.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060307
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  • 19
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of electron transfer reactions of aquo-thallium(III) and coordinated thallium(III). Reduction of thallium(III) and chlorothallium(III) complexes by L-ascorbic acid in aqueous acid medium (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 179-186 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The stoichiometry of the reaction of TIIII with ascorbic acid (H2A) in the presence and absence of chloride ion conforms to TIIII + H2A 〉 TII + 2H+ + A. where A is dehydroascorbic acid. The reaction exhibits complex kinetics and the reactivity of various chlorothallium (III) species decreases in the order of [TIOH]2+ 〉 TI3+ 〉 [TICI]2+ 〉 [TICI2]+ 〉 TICI3 〉 [TICI4]-. The mass balance relationship was employed to calculate the equilibrium concentration of the chloride ion for evaluation of the rate constants.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060309
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  • 20
    Electronic Resource
    Electronic Resource
    IUPAC Commission on Physical Organic Chemistry (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 193-194 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060311
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  • 21
    Electronic Resource
    Electronic Resource
    Theoretical studies of substituent effects on thermal eliminations of aryl ethyl carbonates and S-aryl O-ethyl thiocarbonatesDetermination of Reactivity by MO Theory. Part 82. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 215-222 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Substituent effects on the thermal elimination reactions of carbonates and thiocarbonates were investigated MO theoretically using the AM1 method. For both substrates, an electron-withdrawing group is found to facilitate the decomposition. A two-step process is favoured by carbonates, whereas one- and two-step processes can compete in the pyrolysis of thiocarbonates. The ability to transmit substituent effect is greater with oxygen (carbonates) than with sulphur (thicarbonates) in contrast to the experimental results of Taylor and co-workers. Modelling studies with replacement of the phenyl ring with a vinyl group are found to be justified in this type of work.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060404
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  • 22
    Electronic Resource
    Electronic Resource
    Radical reactions of epoxides. 2.For Part 1, see Ref. 1. intramolecular competition between cyclopropylmethyl and oxiranylmethyl radical ring-opening rearrangementsInitial results presented at the 46th Northwest Regional Meeting of the American Chemical Society, LaGrande, OR, 1991. Taken from the Thesis of K. W. Krosley.2 (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 228-232 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The erythro-thioimidazole precursor to the cyclopropyloxiranylmethyl radical has been prepared. Treatment with 7-19 equiv. of triphenyltin hydride at 70°C gave only 3-cyclopropylprop-2-en-1-ol, the product of epoxide ring opening. No product in which the cyclopropyl ring had opened was observed. Kinetic analysis allowed the assignment of a lower limit for the rate of oxiranylcarbinyl radical rearrangements of 1 × 1010 s-1 at this temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060406
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  • 23
    Electronic Resource
    Electronic Resource
    Calorimetric study of human serum albumin in water-dioxane mixtures (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 251-253 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The calorimetric isotherm of water sorption by solid human serum albumin (HSA) was measured in water-dioxane mixtures. This isotherm has been successfully described at low water contents in the solvent within the framework of the presented model. The adsorption equilibrium constant and the monolayer formation energy were estimated from this model. The interaction enthalpies of solid HSA with the solvent in water-rich mixtures do not differ essentially from the solution enthalpy of HSA in water. This means that the solvent water content may be sufficient for the intermolecular interactions of HSA suspended in a water-organic mixture to be similar to those in aqueous protein solution.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060409
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  • 24
    Electronic Resource
    Electronic Resource
    Crystal and moecular structure of N-nitro-N-methyl-p-nitroaniline: Analysis of substituent effects on the ring geometry and estimation of the Hammett substituent constant for the N-methylnitramino group (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 257-260 
    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 structure of N-nitro-N-methyl-p-nitroaniline was solved with good precision: R = 0·058 and average estimated standard deviation for bond lengths = 0·003 Å. Analysis of the geometry reveals that the NO2 attached to the N atom is strongly conjugated. Application of the HOSE model to its geometry and to geometries of 12 other para-substituted nitrobenzenes yields good linear regressions between canonical structure weights and Hammett σ values by interpolation, σ for the N(Me)NO2 group is estimated to 0·36.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060502
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    The Marcus cross relation for hydrogen-transfer reactions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 281-286 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Marcus cross relation provides a tool to calculate cross rates from the corresponding identity rates and the equilibrium constant. Assumptions made in deriving the Marcus cross relation and conclusions which can be drawn from agreement or disagreement between experimental and calculated cross rates are discussed. For a small variation in identity rate constants, agreement between experimental and calculated cross rates are discussed. For a small variation in identity rate constants, agreement between experimental and calculated cross rates simply means that the rate constant of a hypothetical thermoneutral cross reaction has a value within the range covered by the identity rates. Whether or not this value corresponds to the mean value of logarithmic identity rate constants can only be checked for a large variation in identity rates. Therefore, a newly defined index M is used to relate the difference in experimental and calculated logarithmic rate constants to the variation in the logarithmic identity rates. Provided that the Marcus cross relation is not obeyed, this indicates non-additivity of kinetic parameters. Applying this analysis to protontransfer reactions between different transition metal acids and between 9-alkylflourenes and (9-alkylfluorenyl)lithium shows that claims about agreement or disagreement of experimental rate constants with the rate constants calculated by means of the Marcus cross relation have to be revised in part.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060505
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    Electronic Resource
    Hydrogen-bond basicity of nitriles (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 302-306 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A thermodynamic hydrogen-bond basicity scale, pKHB, and a spectroscopic hydrogen-bond basicity scale, Δν(OH), were measured which permitted the construction of the solute hydrogen-bond basicity scale, β2H, for 71 nitriles embracing a wide range of structures from trichloroacetonitrile to cyanamides. Field, resonance, and polarizability contributions of the X substituents to the hydrogen-bond basicity of XCN compounds were established. Steric effects do not contribute to the hydrogen-bond basicity of nitriles.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060508
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060601
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  • 28
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    Interaction of 3,4-diphenyl-1,2,5-thiadiazole 1,1-dioxide with proton donor solvents (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 341-346 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The UV spectra of 3,4-diphenyl-1,2,5-thiadiazole 1,1-dioxide (I) and that of its thiadiazoline and thiadiazolidine derivatives were measured in several aprotic and protic solvents. Strong specific interactions of I with protic solvents are observed and the formation of stable carbinolamine type derivatives of I with methanol or ethanol is proposed. Spectroscopic data (UV, 1H and 13C NMR) and electrochemical evidence for their formation are given and a new thiadiazoline derivative of I (3-ethoxy-2-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide) was synthesized. The equilibrium constant for the reaction of I with ethanol is reported.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060605
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    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.
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    URL: http://dx.doi.org/10.1002/poc.610060608
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  • 30
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    Nucleophilic substitution reactions of isopropyl benzenesulphonates with anilines and benzylamines (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 357-360 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The nucleophilic substitution reactions of isopropyl arenesulphonates with anilines and benzylamines in acetonitrile at 65·0°C were investigated. The cross-interaction constants ρxz (and βxz) between substituents in the nucleophile (X) and leaving group (Z) are positive and relatively small. The transition state (TS) variation is consistent with that predicted by the More O'Ferrall-Jencks diagram, as expected from the positive ρxz. The small magnitude of ρxz correctly reflects a relatively loose TS structure, in contrast to the tight TS for ethyl (or methyl) derivatives under similar reaction conditions.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060607
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  • 31
    Electronic Resource
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060701
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    Tuning intramolecular carbenic insertions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 376-379 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 1,2-carbenic hydride shift of neopentylmethoxycarbene was suppressed by the methoxy substituent. Thermally activated hydride shifts were observed with phenoxymethylmethoxycarbene and phenoxymethyltrifluoro-ethoxycarbene, where appropriate potentiating substituents were introduced at both the migration origin and the migration terminus. Similarly, the 1,3-CH insertion reaction of tert-butylfluorocarbene could be induced by thermal activation.
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    URL: http://dx.doi.org/10.1002/poc.610060611
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    Ion-molecule pairs as intermediates in solvolysis. Catalysis by the pyridine leaving group on the elimination reaction (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 374-375 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvolysis of the 1-(1-methyl-1-phenylethyl)pyridinium cation (1-P+) in 25% (v/v) acetonitrile in water at 60°C provides the alcohol 2-hydroxy-2-phenylpropane (1-OH) as the main product along with the alkene 2-phenylpropene (3). The formation of the elimination product 3 is promoted by the leaving pyridine. Thus, eight times more 3 is obtained from 1-P+ than from the protonated ether 1-OMeH+. Hydron abstraction by the leaving pyridine is only two times less efficient than with AcO- as leaving group. The results indicate that the ion-molecule pair 1+ -P has a significant lifetime. The elimination product is formed mainly from the ion-molecule pair. The free carbocation yields almost exclusively the substitution product.
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    URL: http://dx.doi.org/10.1002/poc.610060610
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    Temprature dependence of the deuterium isotope effect in the deprotonation of some nitroalkanes by anionic bases (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 393-398 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The temperature dependences of rates and deuterium isotope effects were determined for the deprotonation of 1-phenyl-1-nitroethane (1), its analogue 1-d, 1-phenyl-2-nitropropane (2) and its analogue 2-d by methoxide in methanol, ethoxide in ethanol, hydroxide/methoxide in 50% (v/v) methanol-water and hydroxide in water. The isotope effects varied little with substrate or solvent-base combination. kH/kD at 30°C was between 6·0 and 7·1 in all cases. The temperature dependences varied considerably [AaH/AaD = 0·14-1·35 and EaD - EaH 0·95-2·29 kcal mol-1 (1 kcal = 4·184 kJ)]. AaH/AaD was lower with 1-phenyl-1-nitroethane than with 1-phenyl-2-nitropropane, but there was no consistent variation with solvent/base.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060703
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    Microwave activation of the mutarotation of α-D-glucose: An example of an interinsic microwave effect (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 407-411 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mutarotation reaction of α-D-glucose in ethanol-water solvent in a modified commercial microwave oven, when compared with control reactions carried out at identical temperatures, shows a non-thermal microwave effect, evidenced both by a more rapid reaction and by a change in relative amounts of α- and β-D-glucose over time.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060705
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  • 36
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    Magnetic field effects upon photochemistry of bifuctional chain molecules (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 381-392 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: External magnetic field effects are discussed for three typical examples of photoreactions involving biradical intermediates: photo-induced intramolecular electron transfer in chain molecules D—(CH2)n—A consisting of an electron donor (D) and an acceptor (A), intramolecular hydrogen abstraction in bifunctional species :X—(CH2)n—YH containing a hydrogen donor (YH) and an acceptor (:X in the excited triplet state) and photochemical homolytic ring opening of a cyclic ketone which yields a biradical consisting of an acyl and an alkyl group. There has been progress in the elucidation of reaction mechanisms through the analysis of magnetic field effects on lifetimes of reaction intermediates and product yields in radical reactions involving biradicals. Extremely small interactions such as the Zeeman energy and hyperfine interaction may give rise to a large change in the distribution of photo-products derived from bifunctional chain molecules.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060702
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    Evidence for the presence of the CH-π-interacted ap-conformers of benzyl formates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 399-406 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to examine the preferred conformations of benzyl, 1-phenylethyl and cumyl formates, lanthanoid-induced shifts (LIS) of 1H and 13C NMR and difference NOE spectra of these esters were measured. The measurements showed that a folded conformer capable of forming intramolecular CH-π interaction are predominant with all three series of formate esters. The LIS and other experiments suggested the coexistence of considerable amounts of extended conformers, however. As the ester group is enforced to take supposedly unfavourable ap-conformation in the CH-π contiguous folded conformer, the predominance of the conformer was a surprise and needed explanation. The NOE experiments on a series of para-substituted benzyl formates, XC6H4CH2OCHO (X = CH3O, CH3, H, Cl, NO2), showed that the enhancement of aromatic proton signals (ortho and meta) induced by the irradiation of formyl proton increases gradually as the substituent becomes more electron donating, whereas the enhancement of benzylic (α) proton signal remains constant irrespective of the nature of the substituent. This can be explained by assuming that the CH-π contiguous folded conformer is in equilibrium with the extended conformer. The trend of the substituent effect supports the hydrogen bond-like nature of the CH-π interaction. A similar trend was also observed with substituted 1-phenylethyl formates. Hence the unexpected stability of the ap-conformer of benzyl formates could be ascribed to the stabilization due to the CH-π interaction.
    Additional Material: 2 Ill.
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    Erratum (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 433-433 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060709
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    Adsorption at the liquid-liquid interface: An important factor in phase-transfer catalysisReactions of Organic Anions, Part 200. For Part 199, see Ref. 1. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 412-420 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new rationalization of some phenomena in the phase-transfer catalysed processes promoted by concentrated aqueous alkali solutions, such as alkylations and β-eliminations, is proposed. It is predicted on the basis of adsorption theory and subsequently evidenced experimentally that the size of the interfacial area, controlled by the rate of stirring, affects the position of the extraction equilibrium of various anions with quaternary ammonium cations supplied by the phase-transfer catalysts.
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    URL: http://dx.doi.org/10.1002/poc.610060706
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  • 40
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    Reactions of cycloalkyl chlorides and bromides with diphenylphosphide ions in liquid ammonia (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 421-426 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reactions of cycloalkyl (butyl, pentyl, hexyl and heptyl) chlorides and bromides with diphenylphosphide ions were studied in liquid ammonia. Cyclobutyl chloride was unreactive, whereas the bromide reacted giving the substitution product cyclobutyldiphenylphosphine (isolated as the oxide) in good yields; this reaction was catalysed by light and partially inhibited by p-dinitrobenzene (p-DNB). Cyclopentyl, cyclohexyl and cycloheptyl chlorides did not react in the dark, but the substitution products were formed under irradiation, and these reactions were inhibited by p-DNB. The bromides reacted in the dark or under irradiation, and these reactions were partially inhibited by p-DNB. It can be then concluded that the reactivity of cycloalkyl halides depends on the ring size and the nucleofugal group. In addition, as the overall reactivity decreases, there is an increase in electron transfer reactions.
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    Vibrational spectra of C4H7+ isomers in low-temprature antimony pentafluoride matrices (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 427-432 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The IR spectra of isomeric bicyclobutonium (1), delocalized cyclopropylcarbinyl (2) and 1-methylally (3) cations were recorded at 180 K in SbF5 matrices. Cations 1 and 2 generated from cyclopropylcarbinyl and cyclobutyl chloride, respectively, rearrange to 3 at temperatures above 230 K. The structures 1, 2 and 3 were confirmed by comparison of the recorded frequencies with the MP2/6-31G*-calculated values. These results are in accord with prediction that ions 1 and 2 are rapidly equilibrating non-classical structures.
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060801
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    Base catalysed photochemically induced hydrogen isotope exchange in o-methylbenzophenone (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 465-470 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photochemically induced hydrogen-deuterium and hydrogen-tritium exchange between o-methylbenzophenone and labelled methanol is shown to be catalysed by sodium carbonate. Both the (E) and (Z)-photoenols participate in the exchange reaction whereas in absence of the catalyst only the (E)-photoenol is reactive. Analysis of the measured quantum yields for hydrogen isotope exchange reaction allowed the determination of the relative population of transient photoenols and to its comparison with that obtained from the flash photolysis experiments. Both hydrogen kinetic and solvent isotope effects are discussed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060804
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    Structural study on 1-phenyl- and 1-(2-naphthyl)-8-tropylionaphthalene hexafluoroantimonates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 435-444 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular structures of 1-phenyl- (5) and 1-(2-naphthyl)-8-tropylionaphthalene (6) hexafluoroantimonates were determined by x-ray crystallography and compared with those of 1,8-diphenylnaphthalene and related compounds. In these compounds, the two aromatic substituents face each other in a nearly parallel conformation with a splayed-out arrangement. In the cations 5 and 6, the distance between the facing rings is appreciably shorter than that of other 1,8-diarylnaphthalenes, suggesting the presence of some attractive force. This attraction is ascribed to an intramolecular charge-transfer interaction, and seems to bring about a slight inward bending of the 2-naphthyl substituent in the cation 6. AM1 calculations were carried out for these cations and the results are discussed in comparison with the results of x-ray crystallography.
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    Structure, stabilization energies and chemical shifts of the cyclobutenyl cation. Does it have ‘aromatic’ homocyclopropenium ion character? An ab initio study (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 445-464 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relatively high stability and the structure of the simplest homoaromatic carbocation, the cyclobutenyl cation 1, was established ab initio by using correlated wave functions at HF 6-31G*, MP2(full)/6-31G*, MP2(full)/6-311G** and MP4(SDQ,full)/6-31G* geometries. The stability of 1 was estimated using homodesmotic and isodesmic reactions. The heat of formation of 1 was estimated to be 244 kcal mol-1 (1 kcal = 4·184 kJ). Chemical shift calculations were carried out at correlated levels and are in good agreement with the experimental values. At all levels of theory chemical shift calculations confirm the bent structure of 1. The MP4(SDTQ,fc)/6-311G**//MP2(full)/6-311G** + ZPE(MP2/(full)6-31G*), QCISD(T,fc)/6-31 + G*//MP2(full)/6-31G* + ZPE(MP2(full)/6-31G*) and MP4(SDQ,full)/6-31G*//MP4(SDQ,full)/6-31G* + ZPE(MP2(full)/6-31G*) ring inversion energies of 9·1, 9·3 and 9·0 kcal mol-1, respectively, agree with experiment (8·4 ± 0·5 kcal mol-1). Triplet electronic states are not competitive energetically. The homoaromatic character of the cyclobutenyl cation is shown by the nearly equal charges on C-1, C-2 and C-3, the considerable 1,3-bond order, the short 1·74 Å C-1—C-3 distance and the large stabilization energy relative to the allyl cation.
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    URL: http://dx.doi.org/10.1002/poc.610060803
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    Protonation of 2-(2-thienyl)pyrrole and 2-(2-thienyl)-1-vinylpyrroles (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 471-477 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 2-(2-Thienyl)pyrrole and its 3-alkyl-1-vinyl derivatives have been shown (1H NMR) to be protonated by HSO3F, CF3COOH, HCl and HBr at the pyrrole C-5 atom. Reaction with the superacid system HSO3F—SbF5-SO2 results in the equilibrium between pyrrolium and thiophenium ions. The heats of formation (ΔH), charges and HOMO partial electron densities for 2-(2-thienyl)pyrrole and its protonated forms have been calculated by the MNDO method. The calculated ΔH values of thienylpyrrolium and pyrrolythiophenium ions are in agreement with the experimentally observed ratio.
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060901
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  • 48
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    Electronic Resource
    Dipole moments and electronic structure of 2,6-bis(dialkylamino) derivatives of 4H-pyran-4-one(thione) and 4H-thiopyran-4-one(thione) (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 489-493 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dipole moments of a series of 2,6-bis(dimethylamino) and 2,6-bis(pyrrolidino) derivatives of 4H-pyran-4-one (2), 4H-thiopyran-4-thione (3), 4H-pyran-4-thione (4) and 4H-thiopyran-4-thione (5) were determined in benzene and dioxane solutions at 25°C. High values of the dipole moments (6·44-8·44 D) and mesomeric moments originated from delocalization of the nitrogen lone pairs into the π-system of the heterocyclic moieties (1·11-3·08 D) indicate a strong polarization of the molecules 2-5 due to a tendency to stabilize pentamethinium and pyrylium (thiopyrylium) ionic structures. The MNDO-calculated electronic distribution in 2-5 compared with that for the parent 4H-pyran(thiopyran)-4-one(thione)s is in line with this conclusion.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060902
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    Electronic Resource
    Photoreaction of 2-benzoylcyclohexanones on a silica gel surface: Deviation from their solution photochemistry (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 494-498 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On irradiation on a dry silica gel surface, 2-benzoylcyclohexanones which have the lowest n, π* state and are devoid of methyl substituents on their cyclohexanone rings, undergo an oxidative cleavage to give adipic acid and subsituted benzoic acid along with the Norrish Type II product. Irradiation of 2-chlorocylohexanone and cyclohexane-1,2-dione on silica gel also gives adipic acid. The cyclohexanonyl radical on the surface, which is produced from the α-cleavage of the 2-benzoyl group of the 2-benzoylcyclohexanones or the cleavage of the C—Cl bond of 2-chlorocyclohexanone, is suggested as the precursor of adipic acid; the radical is probably converted into cyclohexane-1,2-dione, which undergoes a secondary photoreaction to give adipic acid on the surface.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060903
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  • 50
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    Electronic Resource
    Multinuclear NMR study of a five-membered ring ditellurium derivative (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 520-522 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 125Te, 1H and 13C NMR data are presented for a five-membered ring ditellurium derivative. The signals are assigned by means of integration and correlation spectroscopy. The NMR data are most consistent with the presence of one of the two possible structures.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060906
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  • 51
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    Calculation of non-linear optical properties of pyridinium cyclopentadienylides (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 531-534 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Finite field/PM3 calculations of the dipole moments, polarizabilities, hyperpolarizabilities, and second-order hyperpolarizabilities of pyridinium cyclopentadienylide and some nitro and amino derivatives suggest that these compounds are good candidates for non-linear optical materials.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060908
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  • 52
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    Theoretical studies of the effects of ortho-methyl substitution on SN1 and SN2 processes at primary and secondary benzylic carbonsDetermination of Reactivity by MO Theory, Part 84. For Part 83, see Ref. 1. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 499-508 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of o-methyl substitution on the transition-state (TS) structure and reactivity of SN1 and SN2 processes were investigated for primary and secondary benzyl (α-tert-butyl) derivatives MO theoretically using the AM1 method. The o-methyl groups have both stabilizing (by electron donation) and destabilizing (steric) effects on the SN2 TS; the former prevails for the primary whereas the latter effect becomes dominant for the secondary compounds. In contrast, complex interplay of the two effects are operative in the SN1 TS of both primary and secondary derivatives leading to the reactivity order which is consistent with that observed by solvolytic experiments, o,o′-dimethyl 〈 H 〈 o-methyl. The bond length-reactivity rule applies only for the primary benzyl SN2 series for which steric effects are insignificant. For reactions of benzyl derivatives is general the coplanarity between the carbenium sp2 centre and the benzene ring, π-σc-x*, is of the utmost importance in stabilizing TS structure for which other structural requirements may be relaxed.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060904
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    Micellar catalysis of organic reactions. Part 34. Nucleophilic aromatic substitution reactions in micelles with bulky head groups (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 535-538 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Observed second-order rate constants for the hydroxydechlorination of 1-chloro-2,4-dinitrobenzene (2), 2-chloro-3,5-dinitrobenzoate ions (3) and 4-chloro-3,5-dinitrobenzoate ions (4) in micelles of cetyltrialkylammonium bromide (C16H33NR3Br, where R = Me, Et, n-Pr and n-Bu) are reported. For substrate 2, the observed catalysis increased as the size of the micellar head group was increased. This was shown to be primarily due to an increase in the rate of reaction in the micellar pseudo-phase (k2M). For substrates 3 and 4, the observed catalysis decreased as the size of the micellar head group was increased. Much smaller changes in k2M were observed in these reactions, which lead to a dianionic intermediate which is more sensitive to polarity effects at the micelle surface than is the monoanionic intermediate formed from 2. These results support the contention that as the size of the micellar head group is increased, water is squeezed away from the micelle surface, resulting in a less polar reaction environment.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060909
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  • 54
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    Electronic Resource
    Photochlorination of tetrachloroethene in carbon tetrachloride solutions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 545-550 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Validation of the mechanism of tetrachloroethene photochlorination at low C2Cl4 concentrations was investigated. The reaction was examined in carbon tetrachloride solution. For initial tetrachloroethene concentrations below 2 mol I-1, the solvent participates in a free-radical chain photochlorination. The presence of CCl4 disturbs the course of this particular chain reaction and influences the duration of the induction period.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061003
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  • 55
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    Heats of formation of organic molecules by ab initio calculations: Alkyl radicals (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 551-554 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A bond and group equivalent scheme that allows the calculation of heats of formation for alkyl radicals from the ab initio restricted open-shell Hartree-Fock 6-31G* energies was developed. For a group of 12 radicals, the rms error for the calculated heats of formation was 0·65 kcal mol-1 (1 kcal = 4·184 kJ). Heats of formation were predicted for the pentyl radical and six of its isomers for which the experimental values are unknown.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061004
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  • 56
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    Solvent effects on initial and transition states in the reaction of m-fluorophenyltriethyltin with mercuric chloride in methanol and methanol-water mixtures (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 561-566 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have investigated solvent effects on the aromatic electrophilic substitution reaction of m-fluorophenyltriethyltin, 1, with mercuric chloride in order to obtain information about the polarity of the transition state. Second-order rate constants have been determined for the reaction of 1 with mercuric chloride in methanol and methanol-water mixtures at 25·0°C, allowing determination of δΔG
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061006
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  • 57
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    Use of the multifunctional autocorrelation method to estimate molar volumes of alkanes and oxygenated compounds. Comparison between components of autocorrelation vectors and topological indices (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 574-582 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Multifunctional Autocorrelation Method (MAM) derived from the autocorrelation method of Moreau et al. was used to calculate molar volumes for 300 linear or branched alkanes from C6 to C11 and 104 oxygenated compounds including 40 alcohols, 30 ethers and 34 ketones. Components Ci of a MAM connectivity vector were compared with several topological descriptors. MAM descriptors were generally more efficient than topological descriptors but good regressions were obtained for alkanes only when more than two components Ci were used. An excellent regression was obtained with four components (C0 to C4): \documentclass{article}\pagestyle{empty}\begin{document}$$ V_{\rm m} = 4 \cdot 45C_0 + 6 \cdot 44C_1 - 3 \cdot 33C_2 + 0 \cdot 46C_4 + 52 \cdot 9{\rm (}n = 300,r = 0 \cdot 999,s = 0 \cdot 81) $$\end{document} Models obtained using descriptors based on connectivity were good enough for many practical purposes. However, to derive models adapted to estimate molar volumes for alkanes, an autocorrelation vector V based on Van der Waals volumes (as given by Bondi) was considered. The best equation obtained again includes three components: \documentclass{article}\pagestyle{empty}\begin{document}$$ V_{\rm m} = 1 \cdot 750V_0 - 0 \cdot 123V_3 - 0 \cdot 037V_4 + 17 \cdot 97{\rm (}n = 300,r = 0 \cdot 999,s = 0 \cdot 85) $$\end{document} To extend the use of MAM to compounds containing heteroatoms, a set of alcohols, ketones and ethers, were each functional group represents a different interaction type, was considered. Chemical families were first studied individually, then the total set was considered. The components of an autocorrelation vector V based on Van der Waals volumes were used as molecular descriptors. Oxygenated compounds are correctly described by only one component V0. The correlation coefficient is 0·993 for all the chemical families studied, and the standard error of the estimate is low (s = 2·56). Comparison of standard errors of the estimate for Wiener's indices (s = 17·38) and autocorrelation components (s = 3·95), for all chemical families, shows that components of MAM are more efficient as molecular descriptors. The quality of regression equations was not significantly changed when 104 oxygenated compounds and 141 alkanes were studied in a global set.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061008
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    Study of initial state and transition state solvation in the Menschutkin reaction of triethylamine with ethyl iodide in alcohols from infinite dilution activity coefficients (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 595-599 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Gibbs energies of activation of the Menschutkin reactions of trethylamine with ethyl iodide in 10 monoalcohols and nine dialcohols, were dissected into contributions from the initial state and transition state. To perform this study, the infinite dilution activity coefficient values of the solutes in the solvents, γ∞, were determined by the UNIFAC group-contribution method, using the modified Flory-Huggins equation in the combinatorial term. For triethylamine, the γ∞ values were calculated using group-interaction parameters from the VLE Parameter Table, due to the nonavailability of specific γ∞ UNIFAC interaction parameters for the relevant groups. For ethyl iodide, the γ∞ values were calculated using the group-interaction parameters from the specific γ∞ UNIFAC Parameter Table, except for the solvents diethylene glycol and triethlene glycol, where VLE parameters were used for the same reasons as explained above for the triethylamine. The results were compared with those obtained for the unimolecular decomposition of tert-butyl halides. For the Menschutkin reaction, we conclude that solvent disruption and reorganization to a state appropriate to solvating the molecular species is a dominant interaction mechanisim.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061011
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  • 59
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    Oxidation kinetics of p-aminodiphenylamine with peroxydisulphate (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 609-614 
    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 oxidation of p-aminodiphenylamine with the peroxydisulphate ion were investigated spectrophotometrically. The oxidation was accompanied by the appearance of a wine-red colour, which changed to become colourless. The reaction rate was measured by the stopped-flow technique with a UV spectrophotometer. The reactions proceeded with second-order kinetics, first-order for each individual reactant. Cationic micelles (cetyltrimethyl ammonium bromide) caused an enhancement in the reaction rate followed by inhibition at higher concentrations. Anionic micelles (sodium dodecyl sulphate), on the other hand, had a slightly retarding effect. The effects of radical scavenger, pH and ionic strength on the fast oxidation rate were examined. A mechanism consistent with the observations is discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061103
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    Structure-odour relations for bitter almond odorants (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 627-633 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Structure-bitter almond odour relations are established for a set of 65 organic compounds (40 having the bitter almond character) belonging to benzene, pyrrole, thiophene, acyclic and cyclic compounds. Compounds are described using components of autocorrelation method, and the odour is described with a binary variable. Data were analysed using principal component analysis followed by a linear discriminant analysis. The obtained model gives satisfactory classification and prediction of the training set and the test set, respectively. In addition, obtained structure-odour relations were translated to structural elements (and rules) necessary for a stimulus to have bitter almond character.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061106
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    Cationic and anionic halochromism (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 637-641 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The spectral changes of organic solutions of N,N,N′,N′-tetramethylenediaminoacetylacetonatocopper(II) perchlorate and a merocyanine dye in the presence of NaI or LiClO4 provide examples of anionic and cationic halochromism, respectively. The observed changes are interpreted as arising from all possible interactions in the three-component system of the dye, the salt and the solvent.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061108
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  • 62
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    The hilbert space formulation of the TLM method (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 29-45 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The Hilbert space representation of the TLM method for time-domain computation of electromagnetic fields and the algebraic computation of the discrete Green's function are investigated. The complete field state is represented by a Hilbert space vector. The space and time evolution of the field state vector is governed by operator equations in Hilbert space. The discrete Green's functions may be represented by a Neumann series in space- and time-shift operators. The Hilbert space representation allows the description of the geometric structures by projection operators, too. The system of difference equations governing the time evolution of the electromagnetic field in configuration space is derived from the operator equation for the field state vector in the Hilbert space.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060105
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    Multiport approach for the analysis of microwave non-linear networks (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 67-81 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The state and output equations of the overall networks are derived from the state and output equations of individual multiports and knowledge of the interconnections between them. A generalized lumped-distributed L/D multiport is described by its associated state, output and non-linear equations in the time domain. Any network can be considered as composed of a set of multiports and independent sources. These equations have been incorporated into a computer-aided procedure for the analysis of L/D networks. The procedure can be used for the simulation of any non-linear microwave circuit and offers the facility of developing a multiport equivalent circuit for any linear or non-linear device or subcircuit. Several examples are successfully analysed using the developed general program.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060107
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    A comparative study of two TLM networks for the modelling of diffusion processes (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 161-164 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A comparative study of two alternative networks for TLM modelling of diffusion processes has been undertaken. Some of their inherent advantages and disadvantages are analysed according to the ratio between the impedance of the lossless transmission lines and the lumped resistance. Their relative accuracy and utility in controlling the timestep automatically are examined.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060208
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    Computer methods in structural analysis, J. L. Meek, E. & F. N. Spon, 1991. 503 pages. Price £25.00, ISBN: 0-419-15440-X (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 167-167 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060210
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    Circuit model for a symmetrical condensed TLM node (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 183-193 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An equivalent circuit for a symmetrical condensed TLM node is presented. The basic circuit has twelve ports and consists of 24 1:1 ideal transformers. Three additional conductances model the conductivity of the medium. The circuit is extended with additional ideal transformers giving six ports for short-circuit and open-circuit stubs which model the permittivity and permeability of the inhomogeneous medium. The scattering matrix of the 18-port network is determined symbolically by solving a set of linear circuit equations. The matrix agrees with previously published results for a symmetrical condensed TLM node, obtained from Maxwell's equations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060303
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    Transmission-line matrix method for solving the multidimensional continuity equation (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 233-236 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: We have extended the one-dimensional transmission-line modelling (TLM) of diffusion, drift and recombination of charge carriers in semiconductors to multiple dimensions. Detailed TLM formulation of the continuity transport equation in a more general form is presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060307
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    A non-linear and distributed modelling procedure of fets (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 237-251 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes a rigorous and systematic procedure to derive a non-linear distributed FET model that can easily be implemented in CAD routines of simulators based on harmonic balance techniques. The new model is derived from a knowledge of the conventional linear lumped equivalent circuit, from non-linear current sources extracted from pulsed measurements, and from the physical dimensions of the FET.For fundamental and harmonic frequencies, the FET is modelled by N identical cells. Each cell is made up of a non-linear two-port section inserted between two linear four-port sections that simulate the coupling and the distributed effects along the electrodes of the FET in the width direction only. This non-linear distributed scaling approach to FET modelling has been applied to the analysis of a submicrometre-gate GaAs FET at millimetre-wave frequencies, and the results were compared with the non-linear lumped element approach. This approach can be applied to other transistors used in non-linear regions at microwave and millimetre-wave frequencies.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060402
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    TLM modelling using an SIMD computer (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 299-304 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A major limitation of the transmission-line matrix (TLM) method used to solve Maxwell's equations is the long computation time required. The TLM scattering calculations involved can, however, be viewed as parallel in nature. This paper describes an effort to reduce computational time by using an SIMD, DAP multiprocessor computer employed to solve a two-dimensional TLM electromagnetic field formulation. A parallel algorithm based on the TLM scattering algorithm is designed and implemented using FORTRAN- PLUS Enhanced on an AMT DAP 510 machine. Here the connectivity of the DAP is exploited to simulate the intrinsic scattering behaviour on which the TLM algorithm relies. The results show that parallel processing on an SIMD machine such as the DAP is advantageous, especially for higher-order mesh sizes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060406
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    Editorial (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 1-1 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060102
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    Calculating frequency-domain data by time-domain methods (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 19-27 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: We show the derivation of parameters in the frequency domain from time-domain data. Far-field characteristics are obtained by a convolution formula with the harmonic field amplitudes, which are obtained via a Fourier transform or by sampling. The electric field of filter ports is expanded into the discrete eigenmodes. By this method, a monochromatic exact open boundary can be formulated and the fields divided into the incident and the reflected part. For wide band operation an a posteriori error correction scheme is presented.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/jnm.1660060104
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    Masthead (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060201
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  • 73
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    Characteristics of a rectangular waveguide containing a magnetized cylindrical ferrite post (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 99-108 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A rigorous formulation of the scattering by a magnetized ferrite in a rectangular waveguide is presented. The EM field depends on the dimension, the frequency and the internal static magnetic field of the ferrite post. For some special values of the above quantitites the reflection or the transmission coefficient becomes equal to zero. These values give a family of filters and the results which follow explain their characteristics.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060203
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  • 74
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    Efficient implementation issues of finite difference time-domain codes for Maxwell's equations (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 195-206 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The computer implementation of time-domain finite difference methods for the solution of Maxwell's equations is considered. As the basis of this analysis, Maxwell's equations are expressed as a system of hyperbolic conservation laws. It is shown that, in this form, all the well-known differencing schemes can be easily expressed, thus increasing the applicability of the implementation issues to be discussed. Practical issues, such as computational efficiency and memory requirements, are discussed for the implementation of the finite difference schemes. Advanced programming techniques in the C language are used to implement the finite difference schemes discussed. The example of the penetration of electromagnetic energy through a shield with a thick gap is used to check the performance of the methods. It is shown that, for cases where the disturbance remains localized in the computational mesh, these techniques result in memory and CPU time savings.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060304
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  • 75
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    Numerical simulation of current-voltage characteristics of silicon photoconductive circuit elements (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 221-231 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Photoconductive circuit elements (PCEs) are suitable for switching applications: they can be turned on and off rapidly, they can conduct a large current in the ‘on’ state when applying a laser or other optical excitation containing high energy photons exceeding the silicon band gap energy, they have a large resistance in the ‘off’ state when the light is off, and they can be fabricated using a simple process. We report the steady- state characteristics of PCEs simulated from a two-dimensional simulator called PISCES-2B. The effects of the conducting channel length, the resistivity of the intrinsic silicon, and the type of contact region on the performance of the PCE will be investigated and discussed. Based on the simulation results, optimal PCE device make-ups will also be suggested.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/jnm.1660060306
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  • 76
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    Masthead (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993) 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060401
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  • 77
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    An extended frequency-domain prony's method for transfer function parameter estimation (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 6 (1993), S. 269-281 
    Details
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The estimation of transfer-function parameters, such as poles and zeros, is useful for characterizing and identifying electromagnetic scatterers. The conventional frequency-domain Prony's technique can estimate these parameters from sampled, frequency-domain data. However, it fails to estimate the true parameters when the sampled data contains contributions from out-of-band poles. In this paper, an extended frequency-domain Prony's technique is developed that circumvents this problem by adding polynomial terms to the standard, Prony pole series. This new technique is shown to be very effective for estimating the poles of transfer functions over very wide bandwidths, without the need for large numbers of simultaneous equations, even when the data are corrupted by noise.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jnm.1660060404
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  • 78
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    Zn2+ complexes with N-(2-pyridyl)cinnamides: Characterization and UV studies (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 15-22 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Zinc(II) complexes of N-pyridylcinnamides (H, m-OCH3, p-OCH3 and p-OH derivatives) were studied by spectrophotometric methods in aprotic media, and represent a chemical model inhibition by cinnamides of coniferyl alcohol dehydrogenase (CAD), a zinc enzyme involved in the lignification process. The complexation of N-pyridylcinnamide and m-methoxy-N-pyridylcinnamide with zinc ion is effected according to a 1 : 1 stoichiometry (ML), whereas a two-step equilibrium (M + L ⇌ ML \documentclass{article}\pagestyle{empty}\begin{document}$ V_{\rm m} = 4 \cdot 45C_0 + 6 \cdot 44C_1 - 3 \cdot 33C_2 + 0 \cdot 46C_4 + 52 \cdot 9{\rm (}n = 300,r = 0 \cdot 999,s = 0 \cdot 81) $\end{document} ML2) is preferred with p-methoxy and p-hydroxy compounds. These ligands are mainly bonded through the carbonyl oxygen atom and the nitrogen of the pyridyl ring. Molar absorptivities for these complexes, not directly available, were calculated from analysis of the experiemental data. The UV complexation results are also supported by the stoichiometry of the complexes, which were synthesized and characterized.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060104
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    Generation of vinyl cations by nitrosation of N-silylated imines and enaminesPresented as a poster at the 10th IUPAC Conference on Physical Organic Chemistry at Technion, Haifa, Israel, August 5-10, 1990. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 44-46 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of monosilylated imines and a disilylated enamine with nitrosyl salts in dichloromethane at -78°C is shown to proceed via intermediate vinyl diazonium salts and vinyl cations.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060107
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060201
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  • 81
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    Ambident reactivity of aryloxide ions towards 1,3,5-trinitrobenzene, low-temperature characterization of the elusive Oxygen-bonded σ-complexes by 1H and 13C NMR spectroscopy (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 71-82 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ambident reactivity of phenoxide ion towards 1,3,5-trinitrobenzene (TNB) was re-examined by means of a novel reaction system(CD3CN-glyme-d10) which allows the investigation of species formed at low temperatures (-40°C), contrasting with previous studies in dimethyl sulfoxide (DMSO) at ambient temperature. The new method coupled with 400 MHz NMR spectroscopy has allowed the definitive observation of both O- and C-bonded phenoxide σ-complex adducts for the first time, confirming the formation of the former through kinetic control and of the latter through thermodynamic control. The corresponding O-bonded σ-adduct in the TNB-mesitoxide system (whereC-bonded σ-adduct formation is not possible but where there is competing nitro group displacement) has also been characterized by 1H and 13C NBR. Another O-bonded aryloxide adduct characterized is that from the reaction of TNB with3,5-di-tert-butylphenoxide; in this system there is also competing NO2 displacement. Stereoelectronic factors in the O-bonded σ-adducts and aryl ethers are discussed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060202
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    Stereochemical features of the (2+2) cycloaddition reactions of chiral allenes. V. Cycloaddition of 1-tert-butyl-3-methylallene with 1,1-dichloro-2,2-difluoroethene (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 95-100 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The (2 + 2) cycloaddtion reactions of 1-tert-butyl-3-methylallene (tBMA) with radicophiles were investigated. The attempted cycloaddition reactions with N-phenylmaleimide, acrylonitrile and methyl acrylate produce only (4 + 2) cycloadducts of 1-tert-butyl-1,3-butadiene which is formed by the more rapid [1.3] hydrogen sigmatropic rearrangement of the tBMA. The (2 × 2) cycloaddition of tBMA with 1,1-dichloro-2,2-difluoroethene (1122) occurs more rapidly than does the sigmatropic rearrangement, and produces a mixture of the four cycloadducts 1-4. The cycloaddition of 1122 with enantioenriched tBMA produces one cycloadduct (3) in which ca 91% of the enantiomeric excess (ee) of the tBMA is transferred to the cycloadduct. The other three cycloadducts are formed retaining much less of the ee of the starting tBMA. The results are interpreted on the basis of molecular modeling calculations carried out on the 1122-1,3-dimethylallene system reported previously. It is suggested that cycloadduct 3 is formed by essentially only one continuous minimum-energy reaction pathway, while cycloadducts 2 and 4 are formed by two competitive minimum-energy reaction pathways which result in the formation of cycloadducts possessing opposite absolute configurations. The combined contributions of the two competitive pathways result in much lower overall degrees of transfer of the ee of the tBMA to the diradical intermediates and cycloadducts.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060205
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    Erratum (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 132-132 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060211
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  • 84
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    Nucleophilic solvent intervention in the solvolysis of 2-aryl-2-Chloropropanes. An example to demonstrate the advantage of using the YBnCl scale in correlation analysis (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 122-125 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The advantage of using the YBnCl scale over the YCl scale in Grunwald-Winstein-type correlation analysis was demonstrated by the kinetic evidence of a significant nucleophilic solvent intervention in the solvolysis of 2-aryl-2-chloropropanes. A depression of log k values measured in ethanol-trifluoroethanol mixtures and a positive azide salt effect were observed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060209
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    Multinuclear NMR and ab initio MO studies of 7-methyl-7H-pyrrolo [2,3-b]pyridine and related compounds (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 139-144 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The contribution of the polarized resonance structures to 7-methyl-7H-pyrrolo[2,3,-b]pyridine and 4-methyl-4H-pyrrolo [3,2-b] pyridine, which have recently attracted much attention in physico-chemical studies, was considered based on multinuclear (1H, 13C and 15N) NMR spectroscopy and MO calculation. Comparison of the chemical shifts of the compounds with those of other relevant compounds and the effects of concentration and solvents observed by multinuclear NMR suggested that the contribution of the non-polarized structures to both compounds predominates over that of the polarized structures. This result was also supported by ab initio MO calculations using the 6-31G basis set.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060303
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    Stern-Volmer quenching kinetics for use of a dualistic quencher (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 160-162 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Stern-Volmer quenching equation for use of a dualistic quencher, which serves not only as the quencher for an excited starting molecule but also as the promoting agent for product formation, was obtained by applying the steady-state approximation to the photoreaction system. The equation was applied to the kinetic analysis of the Norrish type II photoreaction of valerophenone using triethylamine, which serves as the excited-state quencher and as the promoting agent for product formation.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060306
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    Versatile packing modes of 9-substituted 9-fluorenols. X-ray crystal structures of 9-methyl-, 9-phenyl-, 9-(1-naphthyl)- and 9-(2-biphenylyl)fluoren-9-ol (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 171-178 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The four studied semi-rigid fluorenol derivatives differ only in the size of the 9-substituents. All four compounds crystallize with two molecules per asymmetric unit and with relatively low crystallographic symmetry [P1 for the 9-methyl derivative (1) and P21/n for the 9-(1-naphthyl) (3) and 9-(2-biphenylyl) (4) derivatives]. Crystal data: 1, a = 8·779(1), b = 11·570(1), c = 11·747(1), α = 91·197(5), β = 104·345(4), γ = 105·848(6)° 2, a = 8·425(1), b = 13·819(1), c = 23·902(2)Å, β = 95·87(1)° 3, a = 15·679(4), b = 8·567(2); c = 23·884(17)Å, β = 92·60(6)° 4, a = 7·770(6), b = 33·766(10), c = 13·649(4)Å, β = 95·30(1)°. Nevertheless, the packing modes are different. The 9-methylfluoren-9-ol molecules, forming H-bonded tetramers with full H-bond saturation, give rise to the lowest packing coefficient among the four compounds. The crystals of the 9-phenyl derivative are built up of H-bonded dimers, whereas those of the bulky 9-naphthyl and 9-diphenylyl derivatives consist of single molecules only. The latter two compounds, however, have a denser packing than the two that contain H-bonded aggregates. The crystal structures are held together mainly by ordinary Van der Waals forces. In the case of 9-biphenylyfluoren-9-ol, the structure seems to be stabilized also by weak H-bond-type interactions from the alcoholic hydroxyl group to the π-electron cloud of an aromatic ring in the neighbouring molecule the O…centroid distances are 3·182(3) and 3·248(4)Å, and in the 9-naphthyl derivative the OH groups are involved in some short (˜3·3Å) intermolecular approach, possibly indicating an electrostatically favourable packing for the compound.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060308
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    Ring-opening reactions. 6.For part 5, see ref. 1. eliminative ring fission of aziridinium and azetidinium ions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 187-192 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reactivity ratio between the three- and four-membered cyclic ammonium ions in ring-opening elimination reactions was measured. The comparison with the analogous ratio obtained in a previous study on ring-opening substitution reactions suggests a substantial difference in the effect of the stereochemical factors governing the two ring-opening reactions and confirms the anomalous behaviour of small rings in the ring-opening substitution reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060310
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    Substituent effects on the kinetic solvent isotope effect in solvolyses of arenesulphonyl chloridesLimitation of the Transition State Variation Model, Part 6. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 223-227 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Hammett type plot of kinetic solvent isotope effect (KSIE = kSOH/kSOD), log(KSIE) vs σ, can be a useful mechanistic tool for solvoltic reactions. The slopes of such straight line plots for para-substituted benzenesulphonyl chlorides in methanol (0·15), water (0·05) and methanol-water (0·05) are interpreted in terms of different reaction channels (general base-catalysed and SN2), in contrast to simple Hammett plots, log kSOH (or log kSOD) vs σ, invariably exhibiting non-linear concave curves.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060405
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  • 90
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    Ab initio studies of the reaction between diazonium ions and water (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 243-250 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ab initio calculations, using the 6-31G* basis set, were performed in order to study the energetics of the electrophilic attack on water by such diazonium ions as methyl-, ethyl- and fluroethyldiazonium. For the first case, an indication of a transition state appears at the Hartree-Fock level, whereas for the other two, the energy is continuously decreasing from reactants to products. When correlation energy was taken into account via single-point MP2/6-31G* calculations, a deep ion-dipole energy minimum was observed for the methyldiazonium ion followed by a low transition state, whereas the other two did not change their energy pattern. On performing the MP2/6-31G* optimization for the methyl species, the Hartree-Fock results were confirmed, with a slight displacement of the transition state toward a shorter CO distance.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060408
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  • 91
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    Photochemical and radiolytic cleavage of 10-methylacridine dimer in solutions and cryogenic glasses (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 254-256 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 10-Methylacridine dimer [(AcrH)2] dissociates into a pair of 10-methylacridyl radicals (AcrH·) on laser excitation (308 nm) in solvents of various polarities. Exposure of (AcrH)2 in methylcyclohexane glass at 77 K to γ-rays of 60Co generates the radical cation (AcrH)2+·. Thermal annealing of the matrix to 90 K results in dissociation of (AcrH)2+· into AcrH· and 10-methylacridinium cation (AcrH+).
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060410
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  • 92
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    Hydrogen bonding of aromatic amines in hydroxylic solvents. Part 1. Absorption spectroscopy of substituted anilines and hydrogen bond-induced rehybridization of trivalent nitrogen atoms.This paper is dedicated to Professor Jiro Tanaka on the occasion of his 63rd birthday. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 261-272 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The longest wavelength absorption band of substituted anilines containing electron-accepting groups is characterized as an intramolecular charge-transfer (ICT) transition. Dual absorption peaks observed for the ICT transition of some para-substituted anilines in a strongly hydrogen-bonding solvent, hexafluoropropan-2-ol (HFP) can be attributed to two inequivalently hydrogen-bonded species with differently hybridized aniline nitrogens in HFP. The hydrogen bond-induced rehybridization causes appreciable changes in the ICT absorption spectra of highly polar aromatic amines. Rehybridization of aromatic amino nitrogens depends on the OH acidity in the solvent molecule and the basicity of the substituted anilines. The geometry of trivalent nitrogens in aryl amines is critically dependent upon the ionization potential of the amino group, the electron affinity of the electron-accepting substituent and the substitution site of the electron-withdrawing group with respect to the amino moiety.
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    URL: http://dx.doi.org/10.1002/poc.610060503
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    Acid-catalysed solvolysis of optically active 1-Phenyl-1-methoxythane. The role of ion- molecule pair intermediates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 287-292 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The acid-catalysed solvolysis of (R)-1-phenyl-1-methoxyethane was studied in mixtures of dilute aqueous perchloric acid and acetonitrile at 50°C. The rate of loss of optical activity (kα) was found to be the same as the rate of solvolysis (ksolv) at both low and high water contents of the solvent. These results are not in accord with literature data on racemization and oxygen exchange of 1-phenylethanol in water, which has been discussed in terms of interconversion of chiral ion-dipole pair intermediates. The mechanistic implications of the results are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060506
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  • 94
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    Electronic Resource
    Substituent effects in carbon-13 NMR spectra of aminopyridines (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 307-315 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR spectra of 45 vicinally substituted 2-, 3- and 4-aminopyridines were investigated. The substituent effects are evidently sensitive to the position of both the substituent and the fixed amino group. In the para position with respect to the substituent, long-range electronic effects are expressed by the dual substituent parameter treatment (DSP), and the resonance contribution is more important than the inductive contribution. Correlation results for the ipso and ortho carbon atoms using the more sophisticated extended DSP equation suggest non-electronic effects of unknown origin.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060509
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  • 95
    Electronic Resource
    Electronic Resource
    Stereochemistry of aminolysis of N-pentafluorophenylcarbonimidoyl dichloride. Crystal and molecular structures of N2-pentafluorophenyl-N1,N1-dibenzylchloroformamidine (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 319-325 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It has been established that the product of the reaction of N-pentafluorophenylcarbonimidoyl dichloride (1) with dibenzylamine, viz. N2-pentafluorophenyl-N1,N1-dibenzylchloroformamidine (4a) is a Z-isomer, whereas according to the concept of stereoelectronic control one might have expected a product with E-configuration. The heat of formation and the geometry of Z- and E isomer of N2-pentafluorophenyl-N1,N1-diethylchloroformamidine (4b) (the latter is a product of the reaction of 1 with diethylamine) were calculated with the semi-empirical MNDO method. The calculated geometry of (Z)-4b was found to be in a good agreement with the experimentally determined structure of 4a. The formation of (Z)-4b is more preferable energetically than that of (E)-4b; the calculated difference in the heats of formation is 2·8 kcal mol-1. Thermodynamic control of the reaction stereochemistry is proposed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060602
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  • 96
    Electronic Resource
    Electronic Resource
    Conformational analysis of substituted perhydro-1,2-oxazolo[3,2-c] [1,4]oxazines by NMR spectroscopy (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 326-332 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 13C NMR spectra of most of the substituted perhydro-1,2-oxazolo[3,2-c] [1,4]oxazines (3) at low temperature showed the presence of two isomers of unequal populations. The major isomer is shown to be the cis isomer {except in 2-hydroxymethyl-2-methylperhydro-1,2-oxazolo[3,2-c] [1,4] oxazine (3e)}, which is in equilibrium with the minor isomer (trans conformer) by a relatively slow nitrogen inversion. Intramolecular hydrogen bonding in oxazines, having 2-hydroxymethyl substituents, is shown to be an important factor in determining the population ratio of the two isomers. The barrier to nitrogen inversion was determined by detailed band-shape analysis of proton and carbon NMR spectra and were in the range 66·3-72·9 kJ mol-1. The chair inversion had been slowed down, in one case, trans-dimethylperhydro-1,2-oxazol[3,2-c] [1,4]oxazine-2,3-dicarboxylate (3j), to show the presence of the two forms of the cis isomers. The barrier to chair inversion is 41·5 kJ mol-1 as determined by proton NMR band-shape analysis of 3j.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060603
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  • 97
    Electronic Resource
    Electronic Resource
    Kinetic studies of solvent and pressure effects on thermal isomerizations of N-phenyl- and N-methylrhodaminelactams (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 478-482 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvent and pressure effects were examined for the isomerization rates of N-phenyl- and N-methylrhodaminelactams (RL-Ph and RL-CH3) from their zwitterionic to the spiro forms. From the pressure dependence of the reaction rate, the activation volumes were estimated to be about 5 cm3 mol-1 for RL-Ph and 3-10 cm3 mol-1 for RL-CH3. It is proposed that there are two rotameric isomers for the coloured zwitterionic forms, and the role of these rotamers in the kinetic effects of solvent and pressure is discussed. The results are consistent with a reaction mechanism involving heterolytic ring closure on activation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060806
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  • 98
    Electronic Resource
    Electronic Resource
    Zero-field splitting versus interelectronic distance in triplet electron spin resonance spectra of localized dinitrenes (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 483-487 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Triplet zero-field splitting parameters were obtained in 2-methyltetrahydrofuran glass at 77 K for phenylene-1,4-dinitrene (1), biphenyl-4,4′-dinitrene (2), (E)-1,2-bis(4′-nitrenophenyl)ethene (3), 1,4-bis(4′-nitrenophenyl)buta-1,3-diene (4) and 1,8-bis(4′-nitrenophenyl)octa-1,3,5,7-tetraene (5). The results were (1) |D/hc| = 0·169 cm-1 |E/hc| = 0·004 cm-1, (2) |D/hc| = 0·189 cm-1, |E/hc| = 0·00 cm-1, (3) |D/hc| = 0·122 cm-1, |E/hc| = 0·00 cm-1, (4) |D/hc| = 0·0865 cm-1, |E/hc| = 0·00 cm-1 and (5) |D/hc| = 0·0442 cm-1, |E/hc| = 0·00 cm-1. All these biradicals are ground-state singlets. Based on the observed decrease in triplet signal intensities as temperature decreases. The substantial magnitudes of |D/hc| for 3-5, despite the large distance between localized nitrene electrons, is much more than can be explained by a simple dipolar interaction between localized electrons, and is attributed at least partly to spin polarization effects on the π-electron clouds of these systems.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060807
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  • 99
    Electronic Resource
    Electronic Resource
    Solvation and metal ion effects on structure and reactivity of phosphoryl compounds. 2. β,γ-Substituted alkylphosphonic esters (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 523-530 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: NMR spectroscopic and conformation analyses ware carried out for five dimethyl β,γ-disubstituted propylphosphonates, YCH2CHXCH2PO3Me2, in five solvents and in acetone containing sodium and magnesium ions. Conformational preferences observed for the rotation about the C1—C2 bond are determined by the attractive interactions between the oxygen containing substituents X (X = OH, OMe) and the phosphoryl group, and are enhanced by the metal ions, presumably via chelation effects. The rotation about the C2—C3 bond yields statistical distribution of the rotamers. For Y = benzoyl, there was no evidence for a competition of the carbonyl group for the intramolecular interactions with X or with a metal ion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060907
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  • 100
    Electronic Resource
    Electronic Resource
    Efficient formation of some amidines by the reactions of aryliminodimagnesium with weakly electron-accepting benzonitrile, N,N-dimethylformamide and related compounds. Features of reactions governed by σ-complexationAryliminodimagnesium Reagents, Part XXIII. For Part XXII, see Ref. 1. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 509-519 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In many reactions of magnesium reagents, including Grignard and aryliminodimagnesium [ArN(MgBr)2, IDMg], the formation of abnormal products via reactions such as radical dimerization, hydrogen abstraction and conjugate 1,4-addition orginating from efficient single electron transfer (SET) is not excluded. In IDMg reactions with benzonitrile and N,N-dimethylformamide in tetrahydrofuran, however, clean reactions took place affording N-arylbenzamidine and N,N′-diarylformamidine via exclusive 1,2-addition and condensation plus replacement, respectively. Some alkyl and arylvinyl cyanides gave the corresponding amidines without 1,4-addition or hydrogen abstraction. These results are the first observation of such reactions of magnesium reagents, and are attributed to a combination of the weak electron-donating ability (EDA) of IDMg with the weak electron-accepting ability (EAA) of nitriles. Although ESR is therefore inapplicable, factors governing the product yields were studied on the basis of effects caused by the addition of strongly coordinating hexamethylphosphoramide and pyridine to the reagent solution, and by addition of nitrobenzenes having a strong EAA. From the results, a large participation of σ-complexation followed by implicit SET in the inner sphere of the complex is proposed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060905
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