Benzene - computational study

Pure computational results indicate that it should be possible to observe bond fixation in angularly distorted benzenes. Structural studies, either experimental or high-level computational, show that simple cyclic annelations are ineffective at inducing such bond fixation. Computational investigations of arenes with bicyclic annelations predict that these systems will show the desired bond fixation, trisbi-cyclo[2.1.1]hexabenzene, is the favored structure. 

The [n]cyclophanes are the archetypal small cyclophanes and, within this area, it is the [n]paracyclophanes (Fig. 1) that have received by far the most attention. A detailed computational study of [4]paracyclophane [1], which has only been prepared as a transient species via matrix isolation [2], was recently reported. An energy difference of 9 kcal mol between it and its Dewar benzene isomer was predicted. This paper also provides a comprehensive summary of the literature of the [n]paracylophanes. 

Computational studies on the n-n stacking problem began with the simplest model the benzene dimer. While not the only possible configurations, the benzene dimer structures most studied are the sandwiches 77s (D f) and 77s (T>6 ), the parallel displaced 77pd, and the T-shaped configurations 77t and 77t. ... 

A number of computational studies have looked at the benzene dimer with multiple substituents, such as 78 and 79 and 80. All of them show an additivity effect (i.e., increased binding) with each new substituent, regardless of whether the substituent is an EWG or an EDG, and regardless of whether the substitution is on one ring or on both rings. This additivity is not seen in the T-shape configuration. ... 

An interesting example is the interaction of benzene with C mim][PF6, which has been investigated by crystallography, neutron scattering and computational studies. 

G. Vitale, C.F. Mellot, L.M. Bull, and A.K. Cheetham, Neutron Diffraction and Computational Study of Zeolite NaX Influence of SHI Cations on its Complex with Benzene. J. Phys. Chem. B, 1997, 101, 4559 1567. 

Periana and coworkers have recently made computational studies with respect to the mechanism of regioselective hydroarylation of alkenes reported by Periana, Matsumoto, and coworkcrs- " induced by the Ph-Ir(acac)2L catalyst in the formation of ethylbenzene. Iridium inserts into the benzene C-H bond, resulting in an oxidative hydrogen migration through transition... 

Perhaps the first serious computational study of nitrogen oligomers was by Engelke, who studied the Ne analogues of the benzene isomers in Fig. 8.4, first at the uncorrelated [11] then at the MP2 [12] level. The uncorrelated calculations suggested that... 

Another computational study of aromaticity was based on -center delocalization indexes ( -DIs) and led to the conclusion that the order of stability within a series of position isomers (here 1,2,3-, 1,2,4-, and 1,3,5-triazine) is not controlled by aromaticity. The least stable isomer was found to be the most aromatic one (relative energies in kcal mol , 6-DIs in parentheses) within that series 1,2,3-triazine 1 (44.0, 2.75), 1,2,4-triazine (27.3, 2.47), and 1,3,5-triazine (0.0, 2.32) for comparison benzene 2.67 <2006T12204> compare Section 9.01.2.8. 

The preparation of iodonium phenolates 410 was first reported in 1977 via a reaction of phenols 409 with (diacetoxyiodo)benzene followed by treatment with pyridine (Scheme 2.119) [553]. The system of an iodonium phenolate is stabilized by the presence of at least one electron-withdrawing substituent on the aromatic ring. Monosubstituted iodonium phenolates 410 are relatively unstable and easily rearrange to iodo ethers 411 under heating. Such a 1,4 aryl migration is a very common phenomenon for iodonium ylides of types 405-408 according to mechanistic and computational studies it is an intramolecular rearrangement via a concerted mechanism [554,555]. 

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