Benzene aromatic stabilization energy

The gas-phase chemistry of borazine B3N3H6 (147) and the conjugate N-protonated acid B3N3H7+ indicates analogies with benzene,189 although the aromatic stabilization energy of neutral borazine is only 30% that of benzene, and the reactivities of benzene and borazine are not similar (Scheme 62). Comparable conclusions were reached when HOMA and Iq aromaticity indices were used.190a... 

An estimate of the aromatic stabilization energy of silabenzene, based on the calculation of the ISE (STO-3G basis set) (78JA6499), concludes that its value is 2/3 of the benzene stabilization energy. Possible ap-... 

The lowering of the aromatic stabilization energy of silabenzene, compared to benzene, leads one to expect that the energy of the antiaromatic stabilization of silacyclobutadiene (253) would be lower than in the case of cyclobutadiene. 

According to ab initio calculations of the energies of the homodesmotic (86) and the hyperhomodesmotic (87) reactions (85CC1121), the aromatic stabilization energy of (286) amounts to, respectively, 51 and 48% of that of benzene ... 

Using the appropriate bond-separation reactions, the UF/3-21G aromatic stabilization energies are calculated to be 47.2, 36.4 and 22.5 kcal mol-1 for 22,11 and 21, respectively, compared to 59.0 kcal mol-1 for benzene503 thus the meta-, para- and ortho-isomers have 80, 62 and 38% of the aromaticity of benzene. The different orders of the thermodynamic stability of the three isomeric disilabenzene and of their aromatic stabilization energies... 

We calculated the ASE as product energies minus reactant energies, as we did for benzene, and it came out negative, which means that the aromatic stabilization energy here is really destabilizing oxirene is antiaromatic [173]. 

Figure 8 Sammon map obtained for the training data set, showing the relative distances between the input variabies [ASE, A, NICS(1)zz, and HOMA] in the original space. The color scale indicates the Euclidean distances between the weight vector of each neuron and the neuron activated by benzene. ASE, aromatic stabilization energy HOMA, harmonic oscillator model of aromaticity NICS, nucleus-independent chemical shift A, magnetic susceptibility exaltation. Reprinted with permission from Aionso and Herradon (2010JCC917). Copyright 2009 Wiiey Periodicais, inc.

Benzene is the prototypical aromatic molecule with 6 n electrons, perfect Z)6h symmetry, aromatic stabilization energy of about 36 kcal/mol, a NICS value of roughly -9 ppm and an appreciable amount of diamagnetic ring current. Aromaticity of an arbitrary molecule is some times judged through its resemblance with benzene via parameters like Polansky index, molecular similarity, Clar s sextet etc. 

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