Cyclobutadiene point group

Cycloaddition reactions, 162-165, 197-198 component analysis, 168 Diels-Alder, 162, 198 ethylene + ethylene, 198 orbital correlation diagram, 198 stereochemistry, 162-163 Cycloalkanols, synthesis, 277 Cyclobutadiene barrier, 91 ground state, 91 point group of, 5 self-reactivity, 97 SHMO, 151 structure, 309-310 Cyclobutane... 

Scheme 33. Generation of the Twin States by Mixing of the Kekule Structures for Benzene (a) and Cyclobutadiene (b) as Archetypal Aromatic and Antiaromatic Species, (c) Transformation Properties of Ki and K2 with Respect to Symmetry Operations of the Dgh and Dih Point Groups...

Cyclobutadiene barrier, 91 ground state, 91 point group of, 5 self-reactivity, 97 SHMO, 151 structure, 309-310... 

Because the concept of struaure is central to chemistry, it is only natural that prediction of molecular geometries has historically been the most frequent area of application for quantum chemical methods. For the most part, these studies can be loosely grouped into two categories. In the first, rather general questions of structure are addressed, such as the point group symmetry of the molecule (e.g., is cyclobutadiene D2h or Other investigations are di-... 

Crystal energy matrix, 307 Crystal Hamiltonian, 294, 307 Crystals, organic molecular, 286, 327 Cube, Cn axes of, 19 commutation of, 23 symmetry operations of, 23 symmetry planes of, 20, 21 Cubic point groups, 66ff Current density, 109 Cyclobutadiene, v molecular orbitals of, 178-179... 

Further examples for tetragonal point groups are the cyclic molecules cyclobutane (CB), cyclobutadiene (CBD), and their radical cations. Depending on whether CB is planar or puckered, the pertinent point group... 

The CpCo complexes, on the other hand, should be more stable due to the presence of the robust and bulky Cp-shield. Unfortunately, however (tetraiodo-cyclobutadiene)CpCo is not available, and there is no obvious synthetic path to make it. But maybe another way to produce CpCo-stabiHzed tetraethynylated cyclobutadiene complexe exists It is known, that 22 a undergoes a rearrangement to 22 d when subjected to the conditions of flash vacuum pyrolysis at elevated temperatures [24]. The driving force behind this rearrangement is twofold first, the steric strain between the two adjacent TMS groups is removed in 22d and second, the TMS groups in 22d are not bound to an -hybridized center but to an sp-hybridized one, which is a more favorable situation from a thermodynamic point of view. 

In the late 1970s no ab initio programs contained algorithms for directly computing IR frequencies or intensities. However, two groups independently (Kollmar and Staemmler and Hess and Schaad ) undertook the calculation of the IR spectrum of 1. This required a point-by-point calculation of the force-constant matrix, but fortunately the high symmetry (D2 ) of cyclobutadiene significantly... 

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