@article{EngelsPeyerimhoffSkell1990, author = {Engels, Bernd and Peyerimhoff, S.D. and Skell, P.S.}, title = {Theoretical study of the potential energy surface governing the stereochemistry in ClC\(_2\)H\(_4\) reactions}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58851}, year = {1990}, abstract = {Large-scale multireference configuration interaction calculations in a double·t·type AO basis including polarization functions are carried out for the potential surface of the ClC\(_2\)H\(_4\9 system. The charge distribution for various extreme points of the surface is discussed. The absolute minimum is found for an asymmetric ClC2H4 structure. The symmetrical bridged nuclear conformation is also found to be stable with respect to dissociation into Cl + C\(_2\)H\(_4\)• The activation energy for rotation about the C-C axis is calculated tobe around 18 kJ/mol, which is comparable tothat for the 1,2 migration {around 26 kJ/mol). The stereochemistry is governed by the fact that addition of CI to C\(_2\)H\(_4\) (or dissociation) is a two-step reaction proceeding through a symmetrica1 intermediate. The direct addition pathway possesses a small barrier of about 8 kJ jmol.}, subject = {Organische Chemie}, language = {en} } @article{KimChristlKochl1990, author = {Kim, E. and Christl, Manfred and Kochl, J. K.}, title = {Charge-Transfer Cycloaddition of Homobenzvalene with Tetracyanoethylene}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58537}, year = {1990}, abstract = {The transient yellow color observed in the cycloaddition of homobenzvalene (HB) with tetracyanoethylene (TCNE) is associated with the charge-transfer complex [HB, TCNE). The deliberate photoexcitation of [HB,TCNE) affords a mixture of charge-transfer cycloadducts (1, 2, and 3) that differs from that obtained in thermal cycloaddition. The relationship of {HB t TCNE•) radical-ion pair (as the critical reactive intermediate in charge-transfer cycloaddition) to the activation process for thermal cycloaddition is discussed.}, subject = {Organische Chemie}, language = {en} } @article{KarnaGreinEngelsetal.1990, author = {Karna, S.P. and Grein, F. and Engels, Bernd and Peyerimhoff, S.D.}, title = {Ab initio configuration-interaction studies of the ground state potential energy and hyperfine coupling constants of \(^{35}\)Cl\(_2^-\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58869}, year = {1990}, abstract = {Potential energy and spectroscopic constants for the X\(^2 \sum^+ _\mu\) ground state of a;, were calculated by configuration-interaction (Cl) methods, using large basis sets with polarization and diffuse functions. From these CI wavefunctions, the isotropic (a\(_{iso}\)) and dipolar (A\(_{dip}\)) components of the hyperfine coupling constant were obtained. The effects of various s, p basis sets, polarization and diffuse functions, as well as the influence of reference configurations and configuration selection thresholds were investigated. The best values obtained are 35·31 G for a\(_{iso}\) and 29·440 for A\(_{dip}\)• tobe compared with experimental values of 37 ± 1 G and 32 ± 1 G, respectively. It is shown that the contributions to a1so of the K and L shells are opposite in sign, differing by about 4 G. Upon vibrational averaging, both a\(_{iso}\) and A\(_{dip}\) move towards smaller values as v increases. An adiabatic electron affinity of 2·46eV was obtained for CL\(_2\) , and a vertical electron detachment energy of 3·71 eV for Cl;.}, subject = {Organische Chemie}, language = {en} } @article{FunkenEngelsPeyerimhoffetal.1990, author = {Funken, K. and Engels, Bernd and Peyerimhoff, S.D. and Grein, F.}, title = {Study of the hyperfine coupling constants of the moleculs NH2, NHD and ND2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58875}, year = {1990}, abstract = {In the present paper we c:alculate tbe magnetic hyperfine couplina constants (hfcc) ai.ID and A11 of the ground states of the isotopes NH2, NHD and ND2 using truncated MR..CI methods. Differences from other theoretical methocls and shortoominp of the truncated Cl approach in calculating tlj10 are studied. Polarization effects wbich detennirae ailo. as weU as a simple model to describe the dipolar hfcc's, are discussed. All results are in. excellent aareement with experimental data. lt is shown that ab initio methods are able to obtain reliable values for otf-diaaonal values of A41 which are difficult to measure experimentaDy.}, subject = {Organische Chemie}, language = {en} } @article{LangHerzogStangletal.1990, author = {Lang, R. and Herzog, C. and Stangl, R. and Brunn, E. and Braun, M. and Christl, Manfred and Peters, K. and Peters, E.-M. and Schnering, H. G. von}, title = {Reaktionen von Homobenzvalenen mit 4-Phenyl-3H-1,2,4-triazol-3,5(4H)-dion, Tetracyanethylen, Chlorsulfonylisocyanat und Schwefeldioxid. Einige konzertierte 1,4-Additionen an eine Vinylcyclopropan-Einheit}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58527}, year = {1990}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {de} } @article{ChristlReuchlein1990, author = {Christl, Manfred and Reuchlein, H.}, title = {Synthesis and NMR Spectra of 2,3-Dihydro-1,3-methanoindene Derivatives and 1,2,3,5-Tetrahydro-1,3-methanopentalene}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58557}, year = {1990}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {en} } @article{ChristlLanzendoerferGroetschetal.1990, author = {Christl, Manfred and Lanzend{\"o}rfer, U. and Gr{\"o}tsch, M. M. and Ditterich, E. and Hegmann, J.}, title = {Cycloadditionen von 1,3,4-0xadiazin-6-onen (4,5-Diaza-alpha-pyronen), 9 - 6-Oxo-5-phenyl-1,3,4-oxadiazin-2-carbons{\"a}ure-methylester - Synthese und Reaktionen mit Norbornen, Norbornadien, Cyclopropenen, Cyclobuten und Benzvalen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58569}, year = {1990}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {de} } @article{ChristlReuchlein1990, author = {Christl, Manfred and Reuchlein, H.}, title = {Synthesen und NMR-Spektren von 2,3-Dihydro-1,3-methanoindenderivaten und 1,2,3,5-Tetrahydro-1,3-methanopentalen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58549}, year = {1990}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {de} }