Aromaticity of Six-Membered Rings with One Heteroatom

Balaban, A. T.

doi:10.1007/978-3-540-68343-8_5

Cited by 18 publications

(15 citation statements)

References 261 publications

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“…These examples confirm the fact that energetic and geometric criteria of aromaticity [24][25][26][27] may lead to contradictory conclusions [16,[28][29][30].…”

Section: Discussionsupporting

confidence: 78%

Local Aromaticity in Benzo- and Benzocyclobutadieno-Annelated Phenanthrenes

Balaban

Gutman

Marković

et al. 2011

Polycyclic Aromatic Compounds

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The effects of benzo-and benzocyclobutadieno-(BCBD-)annelation on the local aromaticity of the central ring (X) of phenanthrene were examined. The local aromaticity of the ring X was estimated using a graph-theory-based index and two geometrybased indices. DFT calculations of phenanthrene congeners showed that many of these molecules are nonplanar, with significant steric strain. All three indices indicate that the effect of benzo-annelation is opposite to that of BCBD-annelation. The deviation of some phenanthrene derivatives from planarity does not influence the effects of annelation. This finding is in accord with some previously reported studies on the dependence of the aromaticity of the ring(s) on distortion from planarity.

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“…These examples confirm the fact that energetic and geometric criteria of aromaticity [24][25][26][27] may lead to contradictory conclusions [16,[28][29][30].…”

Section: Discussionsupporting

confidence: 78%

Local Aromaticity in Benzo- and Benzocyclobutadieno-Annelated Phenanthrenes

Balaban

Gutman

Marković

et al. 2011

Polycyclic Aromatic Compounds

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“…According to Sastry et al values we reported at the beginning: 1a (−12.8 ppm), 3a (−10.0 ppm), 5a (−12.4 ppm) and 7a (−11.4 ppm). [3,4] Our values are smaller but proportional to those of Sastry et al [3,4] (84%), and his 1/2a > 5/6a > 7/8a > 3/6a order is respected. The correlation values with σ p + are poor (R 2 ≤ 0.8; Krygowski et al noted the same trend for their set of monosubstituted benzenes).…”

Section: Nicssupporting

confidence: 54%

“…Sastry et al have reported the NICS(0) and NICS(1) of the four parent compounds: 1a (−11.5 and −12.8 ppm), 3a (−10.0 and −10.0 ppm), 5a (−9.6 and −12.4 ppm) and 7a (−9.5 and −11.4 ppm), respectively. [3,4] Considering the more reliable NICS(1) values, the aromaticity decreases in the order of 1a > 5a > 7a > 3a, all of them being aromatic. Baldridge et al reported a comprehensive high-level (up to coupled cluster) theoretical study of all silabenzenes (from SiC 5 H 6 to Si 6 H 6 ).…”

Section: Introductionmentioning

confidence: 97%

A theoretical NMR study of ortho and para-substituted benzenes compared with silabenzenes, pyridines and phosphabenzenes

Alkorta

Elguero

2010

Magn. Reson. Chem.

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The experimental spin-spin coupling constants (SSCCs) for 1,3- and 1,4-difluorobenzene have been determined anew, and found to be consistent with previously determined values. SSCCs for 1,2-, 1,3-, and 1,4-difluorobenzene have been analyzed by comparing them with the coupling constants computed using the second-order polarization propagator approximation (SOPPA) and the equation-of-motion coupled cluster singles and doubles method (EOM-CCSD). Eighty experimental values have been analyzed using SOPPA calculations, and a subset of 40 values using both SOPPA and EOM-CCSD approaches. One-bond coupling constants (1)J(C-C) and (1)J(C-F) are better described by EOM-CCSD, whereas one-bond (1)J(C-H) values are better described by SOPPA. An empirical equation is presented which allows for the prediction of unknown coupling constants from computed SOPPA values. A similar approach may prove useful for predicting coupling constants in larger systems.

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“…[8][9][10][11] However, because of the so-called multidimensional character of aromaticity, [12][13][14][15][16][17][18][19] a quantitative measure requires the presence of several attributes, and this complicates quantitative assessments of the concept. One should note, however, that this multidimensional character has been discussed mostly for conjugated heterocycles, [20][21][22] whilst the present paper is about benzenoid hydrocarbons. Furthermore, in addition to the global diamagnetic anisotropy, local π-electron ring-current intensities can be determined for each ring [1][2][3][4]8 of a conjugated network -in our case, a benzenoid system.…”

Section: Introductionmentioning

confidence: 94%

Correlations between Topological Ring-Currents, π-Electron Partitions, and Six-Centre Delocalisation Indices in Benzenoid Hydrocarbons

Balaban¹,

Mallion²

2012

Croat. Chem. Acta

119

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Abstract. Comparison is made between three different indices that characterise the individual rings of a wide range of condensed benzenoid hydrocarbons. Two of these ("π-electron partitions" and the six-centre delocalisation-indices that have been called "Δ 6 -values") have been introduced only recently as potential indicators of what might be called "local aromaticity", whilst the third ("topological π-electron ringcurrents") was suggested as a possible discriminator in this regard nearly fifty years ago. Whilst linear correlations between ring currents and π-electron partitions within certain restricted classes of ring types are good (with correlation coefficients of up to 0.998), agreement between the two indices over all classes of ring types is poor. Predictions arising from a consideration of π-electron partitions and Δ 6 -values seem, on the other hand, to be in somewhat better accord. It is therefore concluded that, despite its superficially intuitive appeal, the ring-current index is out of step both with π-electron partitions and Δ 6 -values as a general indicator of so-called "local aromaticity". (doi: 10.5562/cca1846)

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Aromaticity of Six-Membered Rings with One Heteroatom

Cited by 18 publications

References 261 publications

Local Aromaticity in Benzo- and Benzocyclobutadieno-Annelated Phenanthrenes

Local Aromaticity in Benzo- and Benzocyclobutadieno-Annelated Phenanthrenes

A theoretical NMR study of ortho and para-substituted benzenes compared with silabenzenes, pyridines and phosphabenzenes

Correlations between Topological Ring-Currents, π-Electron Partitions, and Six-Centre Delocalisation Indices in Benzenoid Hydrocarbons

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