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  • Physical Chemistry  (7)
  • Computational Chemistry and Molecular Modeling  (3)
  • Molecular electrostatic potential  (1)
  • 1
    Electronic Resource
    Electronic Resource
    MEPSIM: A computational package for analysis and comparison of molecular electrostatic potentials (1993)
    Springer
    Journal of computer aided molecular design 7 (1993), S. 337-347 
    Details
    ISSN: 1573-4951
    Keywords: Molecular electrostatic potential ; Computational chemistry software ; Molecular alignment ; Molecular similarity ; Spearman coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary MEPSIM is a computational system which allows an integrated computation, analysis, and comparison of molecular electrostatic potential (MEP) distributions. It includes several modules. Module MEPPLA supplies MEP values for the points of a grid defined on a plane which is specified by a set of three points. The results of this program can easily be converted into MEP maps using third-parties graphical software. Module MEPMIN allows to find automatically the MEP minima of a molecular system. It supplies the cartesian coordinates of these minima, their values, and all the geometrical relationships between them (distances, angles, and dihedral angles). Module MEPCOMP computes a similarity coefficient between the MEP distributions of two molecules and finds their relative position that maximizes the similarity. Module MEPCONF performs the same process as MEPCOMP, considering not only the relative position of both molecules but also a conformational degree of freedom of one of them. The most recently developed module, MEPPAR, is another modification of MEPCOMP in order to compute the MEP similarity between two molecules, but only taking into account a particular plane. The latter module is particularly useful to compare MEP distributions generated by π systems of aromatic rings. MEPSIM can use several wavefunction computation approaches to obtain MEP distributions. MEPSIM has a menu type interface to simplify the following tasks: creation of input files from output files of external programs (GAUSSIAN and AMPAC/MOPAC), setting the parameters for the current computation, and submitting jobs to the batch queues of the computer. MEPSIM has been coded in FORTRAN and its current version runs on VMS/VAX computers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125507
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  • 2
    Electronic Resource
    Electronic Resource
    Gas phase thermolysis of N-(tert-butylthio)allylamine and N-(tert-butylthio)diethylamine (1994)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 585-590 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The title sulphenamides were pyrolysed in a stirred-flow reactor at temperatures of 310-410°C, pressures of 8-15 Torr and residence times of 0·4-2 s using toluene as the carrier gas. N-(tert-Butylthio)allylamine formed 73 ± 4% isobutene, 23 ± 3% propene and N-allylthiohydroxylamine. The first-order rate coefficients for the formation of isobutene and propene, respectively, followed the Arrhenius equations kC4(s-1) = 1012·52 ± 0·36 exp(-163 ± 5 kJ mol-1 RT) and kC3(s-1) = 1010·99 ± 0·29 exp(-151 ± 4 kJ mol-1 RT) N-(tert-Butylthio)diethylamine gave 97 ± 1% isobutene, 1·9 ± 0·4% isobutane and N,N-diethylthiohydroxylamine. The first-order rate coefficients for isobutene elimination followed the Arrhenius equation k(s-1) = 1013·45 ± 0·24 exp(-164 ± 3 kJ mol-1 RT). The formation of the products is interpreted in terms of an elimination reaction with a unimolecular, four-centered, cyclic transition state. The reactivity of these sulphenamides was found to be much higher than that of previously studied alkyl or aryl tert-butyl sulphides and disulphides.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610071102
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  • 3
    Electronic Resource
    Electronic Resource
    Gas phase thermolysis of allyl cyanomethyl amine, diallyl cyanomethyl amine, diethyl cyanomethyl amine, and diethyl propargyl amine (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 27 (1995), S. 99-108 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title amines were pyrolyzed in a stirred-flow reactor at 380-510°C, pressures of 8-15 torr and residence times of 0.3-2.4 s, using toluene as carrier gas. The substrates with an allyl group yielded propene and iminonitriles as reaction products. HCN is formed by decomposition of the iminonitriles. The first-order rate coefficients for propene formation fit the Arrhenius equations Allyl cyanomethyl amine:\documentclass{article} \pagestyle{empty} \begin{document} $$ k({\rm s}^{ - {\rm 1}}) = 10^{13.29 \pm 0.35} {\rm exp(} - {\rm 189} \pm 5{\rm kJ/mol }RT{\rm)} $$ \end{document}Diallyl cyanomethyl amine:\documentclass{article} \pagestyle{empty} \begin{document} $$ k({\rm s}^{ - {\rm 1}}) = 10^{13.00 \pm 0.20} {\rm exp(} - {\rm 183} \pm 3{\rm kJ/mol }RT{\rm)} $$ \end{document} Diethyl cyanomethyl amine gave a 20:1 gas mixture of ehylene and ethane, plus HCN. The liquid product fraction contained mainly N-ethyl methanaldimine. The first-order rate coefficients for ethylene formation followed the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - {\rm 1}}) = 10^{15.30 \pm 0.24} {\rm exp(} - {\rm 226} \pm 3{\rm kJ/mol }RT{\rm)} $$\end{document} Diethyl propargyl amine decomposed cleanly into allene and N-ethyl ethanaldimine. The first-order rate coefficients for allene formation fit the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - {\rm 1}}) = 10^{12.84 \pm 0.30} {\rm exp(} - {\rm 168} \pm 4{\rm kJ/mol }RT{\rm)} $$\end{document} The results suggest that the above allyl and propargyl amines decompose unimolecularly by mechanisms involving six-center cyclic transition states. For diethyl cyanomethyl amine, a nonchain free radical mechanism is proposed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550270203
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  • 4
    Electronic Resource
    Electronic Resource
    Gas-phase thermolysis of t-butylsulfenamides: N, N-dimethyl t-butylsulfenamide, 2,6-dimethylpiperidinyl t-butylsulfenamide, and N-t-butyl t-butylsulfenamide (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 28 (1996), S. 353-359 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The amide derivatives of t-butylsulfenic acid mentioned in the title have been thermolyzed in a stirred-flow reactor at temperatures of 273-390°C and pressures of 7-15 torr, using toluene as carrier gas, at residence times of 0.4-2 s. Isobutene formed in 95-99% yields, through order one reactions, following the Arrhenius equations: N, N-dimethyl t-butylsulfenamide: $$k(s^{-1})=10^{14.45\pm 0.46}\exp(-175\pm 5 {\rm kJ/mol}\,{\bf RT})$$ 2,6-dimethylpiperidyl t-butylsulfenamide: $$k(s^{-1})=10^{14.38\pm 0.26}\exp(-161\pm 3 {\rm kJ/mol}\,{\bf RT})$$ N-t-butyl t-butylsulfenamide: $$k(s^{-1})=10^{14.75\pm 0.37}\exp(-184\pm 7 {\rm kJ/mol}\,{\bf RT})$$These thermolyses are considered to take place through unimolecular, four-center cyclic transition-state reaction mechanisms, giving rise to isobutene plus the corresponding S-unsubstituted thiohydroxylamines. The latter decompose outside the reactor at temperatures above -78°C forming free sulfur and dimethylamine, 2,6-dimethylpiperidine, and t-butylamine, respectively. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.4
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  • 5
    Electronic Resource
    Electronic Resource
    Gas phase thermolysis of aryl t-butyl amines (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 631-638 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-t-butylaniline, N-t-butyl-p-anisidine, and N-t-butyl-p-nitroaniline have been pyrolyzed in a stirred-flow reactor at 510-620°C, 8-15 torr total pressure, and 0.5-1.5 s contact time, using toluene as carrier gas. An order one kinetics was observed for the consumption of the amines. The reactions yielded 95 ± 2% isobutene plus the corresponding anilines as reaction products. The rate coefficients followed the Arrhenius equations N-t-butylaniline \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 10^{14.19 \pm 0.32} \exp (- 234 \pm 5\,{\rm kJ/mol}\, RT) $$\end{document} N-t-butyl-p-anisidine \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 10^{13.05 \pm 0.23} \exp (- 208 \pm 4\,{\rm kJ/mol}\, RT) $$\end{document} N-t-butyl-p-nitroaniline \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 10^{13.73 \pm 0.28} \exp (- 235 \pm 6\,{\rm kJ/mol}\, RT) $$\end{document}The results are consistent with an unimolecular elimination of isobutene involving polar four-center cyclic transition states. © John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550240703
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  • 6
    Electronic Resource
    Electronic Resource
    Gas-phase thermolysis of N-cyanomethyl-N-ethyl aniline, N-cyanomethyl-N-ethyl-p-anisidine, and N-cyanomethyl-N-ethyl-p-nitroaniline (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 451-456 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-cyanomethyl-N-ethyl aniline (CEAN) and N-cyanomethyl-N-ethyl-p-anisidine (CEPA) have been thermolyzed in a stirred-flow reactor, in the range of 510-560 °C, pressures of 7-11 torr and residence times of 0.5-0.9 s, using toluene as carrier gas. N-cyanomethyl-N-ethyl-p-nitroaniline (ECNA) was thermolyzed at 640°C and 13% conversion. Ethylene and HCN formed in 43% yield each as products from all three starting materials. Phenyl methanaldimine and p-anisidyl methanaldimine were also products of CEAN and CEPA, respectively. The consumption of CEAN and CEPA showed first-order kinetics for a three-fold increase of reactant inflow and initial conversions of up to 40 percent. The following Arrhenius equations were obtained from the rate coefficients for the production of ethylene: CEAN: k=1015.10±0.74 exp(-238±11 kJ/mol·RT); CEPA: k=1015.61±0.29 exp(-246±4 kJ/mol·RT). The results are explained by means of radical, nonchain thermolysis mechanisms. The thermochemistry of relevant reaction steps has been estimated from thermochemical parameters calculated by using the semiempirical AM1 method. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 451-456, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Semiempirical study of compounds with intramolecular O—H…O hydrogen bonds. II. Further verification of a modified MNDO method (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 183-189 
    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: In the forerunner of this article, we described a MNDO modification designed for studies of compounds with intramolecular O—H…O hydrogen bonds. Here, we report the further verification of the modification by means of its application to 14 compounds not considered in its development. Comparison of the calculated structural parameters and proton transfer characteristics with available experimental or ab initio results, and with those obtained using MNDO, AM1, MNDO/H, MNDO/M, and PM3, supports the validity of the new modification for prediction of hydrogen bond characteristics. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540150208
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  • 8
    Electronic Resource
    Electronic Resource
    Semiempirical study of compounds with O-H—O intramolecular hydrogen bond (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 860-866 
    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: Application of MNDO, AM1, PM3, MNDO/H, and MNDO/M methods to a set of compounds with intramolecular hydrogen bonds suggested that none of these methods accurately modeled the characteristics of the hydrogen bonds. Since the MNDO/H and MNDO/M methods work well for intermolecular hydrogen bonds, we followed their example and modified MNDO for intramolecular hydrogen bonds by altering the empirical core-core repulsion energy function for all pairs of atoms involved in intramolecular O-H—O bonds. The resulting modified method models the behavior of these bonds quite well, especially as regards their geometry and the barrier to proton transfer. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130710
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  • 9
    Electronic Resource
    Electronic Resource
    Quantitative comparison of molecular electrostatic potential distributions from several semiempirical and ab initio wave functions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 14 (1993), S. 922-927 
    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: A quantitative comparative analysis of molecular electrostatic potential (MEP) distributions generated from different wave functions was carried out. Wave functions were computed by using MNDO, AMl, STO-3G, 3-21G, 4-31G, 6-31G, 4-31G*, 6-31G*, and 6-31G** methods. Ten different compounds, which include usual atoms and groups of biomolecules, such as hydroxyl, carbonyl, amine, amide, imine, double and triple bonds, and heteroaromatic rings, were studied. For each compound, MEP values in the points of a common 3-D grid were computed; thereafter, the similarity between each pair of MEP distributions generated by different methods was assessed. Similarities were measured using the Spearman rank correlation coefficient. A similarity matrix was obtained for each compound. Similarity matrices were averaged and a hierarchical cluster analysis was carried out to classify the different quantum chemical methods. In the compounds studied, the main conclusion is the negligible difference between the pattern of MEP distributions generated from all split valence basis sets (with and without polarization functions). © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540140807
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  • 10
    Electronic Resource
    Electronic Resource
    Gas-phase thermolysis of allyl propargyl amine, allyl cyanomethyl propargyl amine, allyl propargyl 2-thiapropyl amine, and allyl methanesulfonyl propargyl amine (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 26 (1994), S. 487-496 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title amines have been pyrolyzed in a stirred-flow reactor, at temperatures of 360-500°C, pressures of 7-16 torr, and residence times of 0.5-2.9 s, using toluene as carrier gas. The reaction products were allene, propene, and the corresponding imines. The ratio allene:propene varied in the range 6.7-1.6. The amines with CH2CN and SO2CH3 substituents also formed HCN and SO2. These appear to arise from complex free radical decomposition of the imine product. The first-order rate coefficients for the production of allene plus propene followed the Arrhenius equations: Allyl propargl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{10.07 \pm 0.31} \exp \left({- 133 \pm 4{\rm kj/mol\,}RT} \right) $$\end{document} Allyl cyanomethyl propargyl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{10.73 \pm 0.30} \exp \left({- 146 \pm 4{\rm kj/mol\,}RT} \right) $$\end{document} Allyl propargyl 2-thiapropyl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{12.55 \pm 0.38} \exp \left({- 166 \pm 5{\rm kj/mol\,}RT} \right) $$\end{document} Allyl methanesulfonyl propargyl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{12.56 \pm 0.34} \exp \left({- 184 \pm 5{\rm kj/mol\,}RT} \right) $$\end{document} Nonconcerted mechanisms, involving polar six center cyclic transition states, are suggested for the elimination of allene and propene. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550260409
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