TY - JOUR A1 - Engels, Bernd A1 - Peyerimhoff, S.D. A1 - Skell, P.S. T1 - Theoretical study of the potential energy surface governing the stereochemistry in ClC\(_2\)H\(_4\) reactions N2 - 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. KW - Organische Chemie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58851 ER - TY - JOUR A1 - Kim, E. A1 - Christl, Manfred A1 - Kochl, J. K. T1 - Charge-Transfer Cycloaddition of Homobenzvalene with Tetracyanoethylene N2 - 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. KW - Organische Chemie KW - Electron transfer KW - photochemical KW - Radical-ion pair KW - Photochemistry Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58537 ER - TY - JOUR A1 - Karna, S.P. A1 - Grein, F. A1 - Engels, Bernd A1 - Peyerimhoff, S.D. T1 - Ab initio configuration-interaction studies of the ground state potential energy and hyperfine coupling constants of \(^{35}\)Cl\(_2^-\) N2 - 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;. KW - Organische Chemie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58869 ER - TY - JOUR A1 - Funken, K. A1 - Engels, Bernd A1 - Peyerimhoff, S.D. A1 - Grein, F. T1 - Study of the hyperfine coupling constants of the moleculs NH2, NHD and ND2 N2 - 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. KW - Organische Chemie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58875 ER - TY - JOUR A1 - Lang, R. A1 - Herzog, C. A1 - Stangl, R. A1 - Brunn, E. A1 - Braun, M. A1 - Christl, Manfred A1 - Peters, K. A1 - Peters, E.-M. A1 - Schnering, H. G. von T1 - 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 T1 - Reactions of Homobenzvalenes wlth 4-Phenyl-3H-1,2,4-trlazole-3,5(4H)-dione, Tetracyanoethylene, Chlorosulfonyl Isocyanate, and Sulfur Dioxide. Several Concerted 1,4-Additions to a Vinylcyclopropane Subunit N2 - No abstract available KW - Organische Chemie KW - 6-Thiatricyclo[3.2.1.o 2.7 ]oct-3-ene 6 KW - 6-dioxide KW - Homo Diels-Alder reactions KW - Cyclopropanetetracarbonitrile derivatives KW - Barbaralane derivatives KW - Urazoles KW - polycyclic Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58527 ER - TY - JOUR A1 - Christl, Manfred A1 - Reuchlein, H. T1 - Synthesis and NMR Spectra of 2,3-Dihydro-1,3-methanoindene Derivatives and 1,2,3,5-Tetrahydro-1,3-methanopentalene N2 - No abstract available KW - Organische Chemie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58557 ER - TY - JOUR A1 - Christl, Manfred A1 - Lanzendörfer, U. A1 - Grötsch, M. M. A1 - Ditterich, E. A1 - Hegmann, J. T1 - Cycloadditionen von 1,3,4-0xadiazin-6-onen (4,5-Diaza-alpha-pyronen), 9 - 6-Oxo-5-phenyl-1,3,4-oxadiazin-2-carbonsäure-methylester - Synthese und Reaktionen mit Norbornen, Norbornadien, Cyclopropenen, Cyclobuten und Benzvalen N2 - No abstract available KW - Organische Chemie KW - 1 KW - 3 KW - 4-0xadiazin-6-ones KW - Diels-Alder reactions KW - y-Oxoketenes KW - ß-Lactones KW - bicyclic KW - Enol Iactones KW - alpha KW - ß-unsaturated Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58569 ER - TY - JOUR A1 - Christl, Manfred A1 - Reuchlein, H. T1 - Synthesen und NMR-Spektren von 2,3-Dihydro-1,3-methanoindenderivaten und 1,2,3,5-Tetrahydro-1,3-methanopentalen N2 - No abstract available KW - Organische Chemie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-58549 ER -