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  • 1
    Electronic Resource
    Electronic Resource
    Ab Initio investigation of the structures and stabilities of CH2N2, CHFN2, and CF2N2 isomers: Important consequences of MP2 optimizations (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 1066-1078 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio calculations of the potential energy surfaces of CH2N2, CHFN2, and CF2N2 at MP4SDTQ/6-31G*//MP2(full)/6-31G* reveal several surprising features. While diazomethane is more stable than diazirine, only the three-membered ring forms of the fluorine-substituted isomers are known experimentally. We find fluorodiazomethane and difluorodiazomethane not to be viable species: They have no barriers toward exothermic dissociation into N2 and CHF or CF2, respectively. In contrast, the three-membered ring isomers, fluorodiazirine and difluorodiazirine, have high barriers toward dissociation despite being high in energy. Diazomethane bends easily; a nonplanar Cs minimum is found at MP2(full)/6-31G* but C2v symmetry is preferred at QCISD/6-31G*. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130905
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  • 2
    Electronic Resource
    Electronic Resource
    An ab initio study of the relative stabilities of the isomers of CH2N2 and SiH2N2 (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 1-8 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio SCF calculations of the equilibrium geometries have been carried out on nine possible isomers of MH2N2, where M = C or Si, and compared with the results of MNDO calculations. The results for the carbon compounds are in good agreement with available experimental data, but in the case of the silicon compounds, the molecules are predicted to be unstable with respect to decomposition to SiH2 and N2. The inclusion of electron correlation at the MP3 level does not alter the order of the relative stabilities, although the importance of the correlation contribution varies substantially between the different isomers.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540040102
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  • 3
    Electronic Resource
    Electronic Resource
    Koopmans' theorem ionization potentials of methyl and silyl halides, chalcogenides, amines, and phosphines: An ab InitioSCF study (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 9-14 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Koopmans' theorem ionization potentials have been calculated for a series of hydrides, methyls, and silyls HnX, (CH3)nX, and (SiH3)nX (X = F, Cl, n = 1; X = O, S, n = 2; X = N, P, n = 3), together with some mixed species (MH3)nXH3-n (X = N, P; M = C, Si) using ab initio SCF methods. The calculated values give excellent agreement with experimental values without the inclusion of d functions. For the chlorides, HCl, CH3Cl, and SiH3Cl, the values vary rather little over a wide range of basis sets, and are unaffected by the inclusion of d functions.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540040103
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of semiempirical MO methods for open-shell systems (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 702-707 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The use of AM1, MNDO, and MNDOC semiempirical MO methods for calculation of heats of formation and ionization potentials of a series of 38 radicals are described. AM1 and MNDO calculations are reported using both half-electron (HE) and Unrestricted Hartree Fock (UHF) wavefunctions. Results show the MNDOC method to give lowest overall errors, being slightly better than the HE-AM1 method. In all cases, the AM1 method shows considerable improvement over MNDO.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090616
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  • 5
    Electronic Resource
    Electronic Resource
    Quantum chemical investigations of charge transfer interactions in relation to the electronic theory of cancer. IV. The interaction of formamide and the enol tautomers of several glyoxals (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 400-406 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The results of ab initio “supermolecule” calculations of the charge transfer between formamide and the enol forms of methylglyoxal, ethylglyoxal, dimethylglyoxal, and propenylglyoxal are compared for several different conformations of the constituent molecules. The enols were found to be poorer electron acceptors than their respective keto isomers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540010411
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum chemical investigations of charge transfer interactions in relation to the electronic theory of cancer. II (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 275-280 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The results of ab initio “supermolecule” calculations of the charge transfer between formamide and methylglyoxal, ethylglyoxal, and dimethylglyoxal are compared for several different relative conformations of the constituent molecules. The charge transfer properties of ethylglyoxal were found to be quite different to those of the other two glyoxals.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540010309
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  • 7
    Electronic Resource
    Electronic Resource
    Ab initio calculations on the effect of different basis sets and electron correlation on the transition state for the reactions HNC ⇌ HCN and BCN ⇌ BNC (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 1-10 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry of the ground states of the isomers and transition state for the systems HCN ⇌ HNC and BCN ⇌ BNC have been investigated using a wide variety of basis sets, both at the self-consistent-field (SCF) level and including correlation at the second-, and third-order Møller-Plesset (MP2 and MP3) levels. The barrier to isomerization and the isomerization energy were shown to be strongly dependent on the basis set and method, particularly for the BCN system.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540050102
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  • 8
    Electronic Resource
    Electronic Resource
    An investigation of the relative stabilities of the isomers of CF2N2: Comparison of ab initio and MNDO calculations (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 1170-1178 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio SCF calculations at the HF/3-21G level and semi-empirical MNDO calculations have been used to locate the stationary points on the CF2N2 energy surface. Perfluorodiazomethane is predicted to be most stable isomer, but perfluorodiazirine is predicted to lie only ca 41 kJ higher in energy at the SCF level. There are significant differences between the ab initio and MNDO results for the ordering of some of the isomers. Frequency calculations give results in good agreement with the limited experimental data on these molecules.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540080814
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  • 9
    Electronic Resource
    Electronic Resource
    A theoretical study of the rotational isomers of nitrosomethanol by semiempirical (AM1) and ab initio methods (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 212-221 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The conformational potential energy surface as a function of the two internal torsion angles in C-nitrosomethanol has been obtained using the semiempirical AM1 method. Optimized geometries are reported for the local minima on this surface and also for the corresponding points on the HF/6-31G, 6-31G*, and 6-31G** surfaces. All methods predict cis and trans minima which occur in degenerate pairs, each pair being connected by a transition state of Cs symmetry. The AM1 structures are found to compare well with the corresponding ab initio structures. Ab initio HF/6-31G and HF/6-31G* harmonic vibrational frequencies are reported for the cis and trans forms of nitrosomethanol. When scaled appropriately the calculated frequencies are found to compare well with experimental frequencies. The ab initio calculations predict the energy barrier for cis → trans isomerization to be between 5.8 and 6.5 kcal/mol with the trans → cis isomerization barrier lying between 2.3 and 6.5 kcal/mol. The corresponding AM1 energy barriers are around 1 kcal/mol lower in energy. The ab initio calculations predict the barrier to conversion between the two cis rotamers to be very small with the AM1 value being around 1 kcal/mol. Both AM1 and ab initio calculations predict interconversion between trans rotamers to require between 1.2 and 1.4 kcal/mol.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090305
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  • 10
    Electronic Resource
    Electronic Resource
    The structure and acid-base properties of methyl and silyl amines and phosphines: An ab-initio SCF study (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 3 (1982), S. 495-506 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The structures of the methyl and silyl amines and phosphines and their ions have been calculated using ab-initio SCF theory and the 3-21G basis set. The computed structures give excellent agreement with the available experiment data without the inclusion of d functions, with the exception of (SiH3)2N- and the isoelectronic molecules (SiH3)2O and (SiH3)2C2- where d functions are essential. The observed trends in computed basicities and acidities are reproduced by the calculations.
    Additional Material: 11 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540030407
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