The application of a new aromaticity index to six-membered ring heterocycles

Bird, C. W.

doi:10.1016/s0040-4020(01)87405-6

Cited by 185 publications

(78 citation statements)

References 35 publications

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“…However, equation (4) cannot be used for the systems with the odd number of bonds (2i + 1). For such systems, the α constant can be calculated from equation (6) or (7). Equation (6) corresponds to the systems possessing (i + 1) single bonds and (i) double bonds, and equation (7) refers to the system having (i) single bonds and (i + 1) double bonds.…”

Section: Homed Indexmentioning

confidence: 99%

“…For such systems, the α constant can be calculated from equation (6) or (7). Equation (6) corresponds to the systems possessing (i + 1) single bonds and (i) double bonds, and equation (7) refers to the system having (i) single bonds and (i + 1) double bonds. In order to properly describe π-electron delocalization in cyclic and acyclic heteroatomic systems, we considered single and double CC, CX, and XY bond lengths in various simple molecules which could be employed as the reference molecules in the modified geometry-based index.…”

Section: Homed Indexmentioning

confidence: 99%

“…Table 4 summarizes the R s , R d , and R o values selected for the HOMED procedure. The normalization α constants calculated according to equations (4), (6), and (7) for even (2i) and odd (2i + 1) number of bonds are given in Table 5. From a mathematical point of view, the procedure of the HOMED index is the same as that of the reformulated and original HOMA index [20][21][22][23][24]31].…”

Section: Homed Indexmentioning

confidence: 99%

“…They depend on the geometry of the system and/or on the type of heteroatom(s) present in the ring [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In the case of five-membered compounds such as pyrrole, furan, and their derivatives, mixed n-π and π-π conjugations are possible.…”

Section: Aromatic Systemsmentioning

confidence: 99%

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On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems

et al. 2010

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Abstract:The HOMA (Harmonic Oscillator Model of Aromaticity) index, reformulated in 1993, has been very often applied to describe π-electron delocalization for mono-and polycyclic π-electron systems. However, different measures of π-electron delocalization were employed for the CC, CX, and XY bonds, and this index seems to be inappropriate for compounds containing heteroatoms. In order to describe properly various resonance effects (σ-π hyperconjugation, n-π conjugation, π-π conjugation, and aromaticity) possible for heteroatomic π-electron systems, some modifications, based on the original HOMA idea, were proposed and tested for simple DFT structures containing C, N, and O atoms. An abbreviation HOMED was used for the modified index.

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Section: Homed Indexmentioning

confidence: 99%

Section: Homed Indexmentioning

confidence: 99%

Section: Homed Indexmentioning

confidence: 99%

Section: Aromatic Systemsmentioning

confidence: 99%

See 2 more Smart Citations

On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems

et al. 2010

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“…In the quantitative evaluation of aromaticity, experimentally determined or theoretically calculated, parameters currently used include: magnetic properties, 2-12 geometry, [13][14][15][16][17][18] bond orders, [19][20][21][22][23][24][25][26][27][28] isodesmic energy, 29 combustion energy, 30 (topological) resonance energy, [31][32][33][34][35][36][37][38] bond lengths [40][41][42][43][44][45][46] etc.…”

Section: Introductionmentioning

confidence: 99%

Aromatic molecular zones and fragments

Tarko¹

2008

Arkivoc

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An edge on the weighted molecular graph is aromatic if the bond order B value is within [α, β] range. A certain "non-conjugated topological path" includes minimum two adjacent "single" edges (B < α). The topological paths that are not "non-conjugated" are "conjugated topological paths". An aromatic zone is a collection of contiguous aromatic edges. An aromatic fragment is a topological path within aromatic zone. The proposed aromaticity formula measures the aromaticity of zones and any "conjugated paths" via two variables that gauge deviations of bond orders from a reference value and of atom hybridization from sp 2 character. The aromaticity of "non-conjugated paths" is, conventionally, null. The analysis of organic/inorganic molecules, ions and radicals, including those having cyclic, non-cyclic, planar and non-planar geometries, uses a unique set of parameters. The larger the deviation from Hückel rules, the smaller (even negative) is the computed aromaticity value. The paper presents a few non-aromatic Hückel and aromatic non-Hückel structures. After geometry optimization by PM6 method, one can compute the value of some aromaticity molecular descriptors, useful in QSPR computations. The paper includes a list of some descriptors that are measurements of the aromaticity of zones and aromatic "conjugated topological paths".

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Electronic Wavefunctions Analysis

Ciosłowski

1998

Encyclopedia of Computational Chemistry

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The application of a new aromaticity index to six-membered ring heterocycles

Cited by 185 publications

References 35 publications

On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems

On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems

Aromatic molecular zones and fragments

Electronic Wavefunctions Analysis

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