-
4
-
-
84989504737
-
-
(b) Indeed, the coincidental overlap of the structural theories of van't Hoff, Kekulé, and Baeyer (ring strain), and the lack of pertinent structural data from diffraction experiments and/or molecular orbital theory, makes the prediction seem reasonable.
-
-
-
-
14
-
-
0000108206
-
Der Effekt angular anellierter, gespannter Ringe auf Benzol: Strukturen von 1,2-Dihydrocyclobuta[a]cyclopropa[c]-, 1,2,3,4-Tetrahydrodicyclobuta[a,c]-, 1,2,3,4-Tetrahydrodicyclobuta[a,c]cyclopropa[e]- und 1,2,3,4,5,6-Hexahydrotricyclobuta[a,c,e]benzol im Kristall
-
(a) 1,2,3,4,5,6‐Hexahydrotricyclobuta[ a,c,e]benzene (1) displayed a bond alternation of 0.023 Å at 125 K
-
(1994)
Angewandte Chemie
, vol.106
, pp. 321-325
-
-
Boese, R.1
Bläser, D.2
Billups, W.E.3
Haley, M.M.4
Maulitz, A.H.5
Mohler, D.L.6
Vollhardt, K.P.C.7
-
18
-
-
0001735890
-
Leichte Hydrierung des zentralen Cyclohexatriens von Tris(benzocyclobutadieno)benzol: Synthese und Struktur sowie thermische und photochemische Isomerisierung von all-cis-Tris(benzocyclobuta)cyclohexan
-
(1990)
Angewandte Chemie
, vol.102
, pp. 1200
-
-
Mohler, D.L.1
Vollhardt, K.P.C.2
Wolff, S.3
-
20
-
-
84989561555
-
-
(c) Similar but less dramatic bond alternation is seen in angular terphenylene. See
-
-
-
-
21
-
-
0000870405
-
Cobalt-katalysierte Cyclisierung von Bis(2-ethinylphenyl)ethin-neue Synthese von gewinkeltem [3]Phenylen (Terphenylen), einem Molekül mit einer Cyclohexatrien-Einheit
-
(1986)
Angewandte Chemie
, vol.98
, pp. 268
-
-
Diercks, R.1
Vollhardt, K.P.C.2
-
25
-
-
11344284526
-
Tables of bond lengths determined by X-ray and neutron diffraction. Part 1. Bond lengths in organic compounds
-
In this context, significance is defined as follows: The length of a C(arom.)‐C(arom.) bond for a hexasubstituted benzene is 1.397 Å, with σ = 0.009 Å; σ for all benzene derivatives is 0.013 Å. A value of ± 3 σ(i.e. ± 0.027–0.039 Å) or greater is considered significant. The values for σ are taken from the Cambridge Crystallographic Database
-
(1987)
Journal of the Chemical Society, Perkin Transactions 2
, vol.2
, pp. S1
-
-
Allen, F.H.1
Kennard, O.2
Watson, D.G.3
Brammer, L.4
Orpen, A.G.5
Taylor, R.6
-
27
-
-
84989534465
-
-
2) = 0.076 and GOF = 1.222 for all 114 observations. All calculations were performed with the programs SHELX93 and XP. Treating the other two data sets in the same way leads to essentially the same, but less accurate results. In the original unit cell the molecular centers would be at 1/3, 1/3, z; −1/3, 0, z; 0, ‐1/3, z; 1/3, 0, z + 1/4; 0, 1/3, z + 1/4; −1/3, −1/3, z + 1/4 (with z = 1/8 and 5/8). For steric reasons and because the translational symmetry perpendicular to the threefold axis is a,b rather than a′,b′, only one of the three alternative positions can be occupied for a given value of z. The basic building blocks of the crystal structure are thus well‐ordered layers of 3, one per unit mesh in a,b, with their threefold axes perpendicular to the a,b‐plane. The layer symmetry group is p62m. The layers above and below any given layer each have a choice governed by probability rules between three alternative, but well‐defined positions; this will be elaborated elsewhere. However, no matter which alternative is chosen, the nearest neighbor relationship between molecules in adjacent layers is always as shown in Figure 2. Since the stacking of consecutive layers is governed by a combination of probability rules and well‐defined nearest neighbor relationships, the crystal shows the observed combination of diffuse and sharp scattering.
-
-
-
-
31
-
-
84989536241
-
-
Alternatively, the total bond order in 3 is 9.75, less than the bond order in benzene (10) but greater than that in hexasubstituted benzenes (9.54) based on the average bond lengths.
-
-
-
-
32
-
-
84989536213
-
-
2CHC=C.
-
-
-
-
33
-
-
84989581605
-
-
The angle distortion effect seems to be nullified in benzenes with monocyclic annelations, like 1, perhaps due to “bent bonds” in those systems; the angular effect for bicyclics appears to be more effective. For an example of a related distortion in the norbornyne trimer, see:, Tetrahedron Lett.
-
(1995)
-
-
Frank, N.L.1
Baldridge, K.K.2
Gantzel, P.3
Siegel, J.S.4
-
34
-
-
84989577076
-
-
Computational details: The molecular structure of 3 was determined at a variety of theoretical methods to determine self‐consistency. Reported here are the split‐valence 6–31G(D) [18] and triple‐zeta valence TZV(D) [19] basis sets, employed at the restricted Hartree‐Fock (RHF) self‐consistent field (SCF) level of theory. These basis sets include a set of six d polarization functions on all heavy atoms. These calculations were performed with the aid of the analytically analytically determined gradients and search algorithms contained in GAMESS [20]. Additional calculations at the MP2/6–31G(D) and Density Functional Theory levels were performed to determine the effects of dynamical correlation. Calculations using the former method, a post‐RHF method that incorporates correlation in terms of Møller‐Plesset theory of order 2 (MP2) [21], were performed using the GAUSSIAN 92 suite of programs [22]. Calculations using Density Functional Theory (DFT) Methods, which inherently incorporate effects of correlation in their development, were performed with the aid of the numerical methods within Dmol [23]. A double numerical basis set augmented by polarization functions, comparable in size to the 6–31G(D) basis set of the traditional Hartree‐Fock methods, was chosen for the DFT calculations.
-
-
-
-
40
-
-
0001968788
-
-
(1990)
QCPE Bull.
, vol.10
, pp. 52
-
-
Schmidt, M.W.1
Baldridge, K.K.2
Boatz, J.A.3
Jensen, J.H.4
Koseki, S.5
Gordon, M.S.6
Nguyen, K.A.7
Windus, T.L.8
Elbert, S.T.9
-
42
-
-
84884501597
-
Gaussian 92, Revision C
-
Gaussian Inc., Pittsburgh, PA
-
(1992)
-
-
Frisch, M.J.1
Trucks, G.W.2
Head‐Gordon, M.3
Gill, P.M.W.4
Wong, M.W.5
Foresman, J.B.6
Johnson, B.G.7
Schlegel, H.B.8
Robb, M.A.9
Replogle, E.S.10
Gomperts, R.11
Andres, J.L.12
Raghavachari, K.13
Binkley, J.S.14
Gonzalez, C.15
Martin, R.L.16
Fox, D.J.17
Defrees, D.J.18
Baker, J.19
Stewart, J.J.P.20
Pople, J.A.21
more..
-
43
-
-
34447260582
-
-
DMol is available commerically from BIOSYM Technologies, San Diego, CA
-
(1990)
J. Chem. Phys.
, vol.92
, pp. 508
-
-
Delley, B.1
|