Energetic Aspects of Cyclic Pi-Electron Delocalization:  Evaluation of the Methods of Estimating Aromatic Stabilization Energies

2005 ◽  
Vol 105 (10) ◽  
pp. 3773-3811 ◽  
Author(s):  
Michał Ksawery Cyrański
Keyword(s):  
Electron Delocalization ◽  
Stabilization Energies ◽  
Aromatic Stabilization

CC/B–N substitution in five membered heterocycles. A computational analysis

2017 ◽  
Vol 41 (9) ◽  
pp. 3619-3633 ◽  
Author(s):  
Vaibhav A. Dixit ◽  
William R. F. Goundry ◽  
Simone Tomasi
Keyword(s):  
Computational Analysis ◽  
Stabilization Energy ◽  
Stabilization Energies ◽  
Neutral Conditions ◽  
Aromatic Stabilization

Novel five-membered azaboroles are aromatic, stable under neutral conditions, isomer stabilization energy is explained using σ-bond and aromatic stabilization energies.

Effects of aromatic stabilization energies of aryl rings of symmetrical diarylethenes

Tetrahedron ◽  
2017 ◽  
Vol 73 (45) ◽  
pp. 6479-6485 ◽  
Author(s):  
Huitao Xu ◽  
Shasha Wei ◽  
Congbin Fan ◽  
Gang Liu ◽  
Shouzhi Pu
Keyword(s):  
Stabilization Energies ◽  
Aromatic Stabilization

A Computational Study of the Conformational Behavior of 2,5-Dimethyl- 1,4-dithiane-2,5-diol and Analogous S and Se: DFT and NBO Study

2020 ◽  
Vol 17 (10) ◽  
pp. 749-759
Author(s):  
Elmira Danaie ◽  
Shiva Masoudi ◽  
Nasrin Masnabadi
Keyword(s):  
Thermodynamic Parameters ◽  
Computational Study ◽  
Structural Parameters ◽  
Nbo Analysis ◽  
Electron Delocalization ◽  
Stereoelectronic Effects ◽  
Conformational Properties ◽  
Molecular Reactivity ◽  
Stabilization Energies ◽  
The Stability

Conformational behaviors of 2,5-dimethyl-1,4-dithiane-2,5-diol (compound 1), 2,5- dimethyl-1,4-dithiane-2,5-dithiol (compound 2) and 2,5-dimethyl-1,4-dithiane-2,5-diselenol (compound 3) were investigated by the B3LYP/6-311+G **, the M06-2X/aug-ccpvdz levels of theory and natural bond orbital NBO analysis. The structures and the structural parameters of the mentioned molecules were optimized by the B3LYP and the M06-2X methods. We assessed the roles and contributions of the effective factors in the conformational properties of the mentioned compounds by means of the B3LYP and M06-2X levels of theory and the NBO interpretations. The stereoelectronic effects of the mentioned molecules were studied using the NBO analysis. The results showed that the stereoelectronic effects were in favor of the (ax,ax) conformers (the most stable conformations), from compound 1 to compound 3; therefore, these effects have impacts on the conformational properties of compounds 1-3, and stabilization energies associated with LP2X→ σ*S1-C2 electron delocalization, where [X= O, S, and Se], for 1-ax, ax conformer has the greatest value between all of the other conformers. Therefore, according to the calculated thermodynamic parameters, the stability of the 1-ax, ax compound was justified by the presence of LP2X→σ*S1-C2 electron delocalization. A molecular orbital explanation was conducted to investigate the correlations between the linear combinations of natural bond orbitals in the HOMOs, LUMOs and the molecular reactivity parameters. There is a direct relationship between the stereoelectronic effects, molecular reactivity and thermodynamic parameters of compounds 1 to 3 as the harder ax, ax conformations with the greater stereoelectronic effects and ΔG(eq-ax) values are more stable than their corresponding eq, eq conformers. Besides frontier molecular orbitals (FMOs), mapped molecular electrostatic potential (MEP) surfaces of conformations of compounds 1 to 3 were investigated.

Acyclic versus cyclic π-electron delocalization. How is the substituent effect related to π-electron delocalization?

2009 ◽  
Vol 74 (1) ◽  
pp. 115-129 ◽  
Author(s):  
Michał A. Dobrowolski ◽  
Jędrzej Kaniewski ◽  
Tadeusz M. Krygowski ◽  
Michał K. Cyrański
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Substituent Effect ◽  
Electron Donors ◽  
Electron Delocalization ◽  
Benzene Derivatives ◽  
Phenol Derivatives ◽  
Stabilization Energies ◽  
Derivatives Of ◽  
Substituted 1

Substituent effect stabilization energies were estimated for sets of 27 para-substituted phenol derivatives, meta- and para-homodisubstituted benzene derivatives, trans-substituted ethenes, 4-substituted 1-hydroxy-1,3-cyclohexadienes and 1,4-homodisubstituted 1,3-cyclohexadienes based on the optimizations at the B3LYP/6-311+G** DFT level of theory. The following substituents were taken into account: C≡CH, C(CN)3, CF3, CH2NH2, CH3, CH=CH2, CHO, Cl, CN, COCH3, COCl, CONH2, COOCH3, COOH, F, NH2, NHCH3, N(CH3)2, NHOH, NO, NO2, OCH3, OH, Ph, H, SH, SO2CN. For hydroxyethenes and phenol derivatives the electron-acceptor substituents stabilize the systems, whereas the electron-donors lead to their destabilization. Both electron-acceptor and electron-donor substituents destabilize homodisubstituted ethene and meta- and para-homodisubstituted benzene species. The strongest destabilization is observed for derivatives of ethene, a weaker one for derivatives of cyclohexadiene and the weakest for benzene derivatives.

Recommendations for the Evaluation of Aromatic Stabilization Energies

2002 ◽  
Vol 4 (17) ◽  
pp. 2873-2876 ◽  
Author(s):  
Paul von Ragué Schleyer ◽  
Frank Pühlhofer
Keyword(s):  
Stabilization Energies ◽  
Aromatic Stabilization

scholarly journals Aromaticities of Five Membered Heterocycles through Dimethyldihydropyrenes Probe by Magnetic and Geometric Criteria

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Maria ◽  
Khurshid Ayub
Keyword(s):  
Chemical Shifts ◽  
Reference Models ◽  
H Nmr ◽  
Quantitative Estimates ◽  
Shift Analysis ◽  
Structural Criterion ◽  
Stabilization Energies ◽  
Suitable Reference ◽  
Chemical Shift Analysis ◽  
Aromatic Stabilization

Aromaticities of five membered heterocycles, containing up to three heteroatoms, are quantified through the dimethyldihydropyrene (DHP) probe. Bond fixation caused by the fusion of heterocycles to the dimethyldihydropyrene nucleus (DHPN) was measured by changes in the1H NMR chemical shifts (magnetic) and bond lengths alterations (structural criterion). Chemical shifts of dihydropyrenes were calculated at GIAO HF/6-31G(d)//B3LYP/6-31+G(d). For1H NMR chemical shift analysis, two nonaromatic reference models are studied. Among the studied heterocycles, pyrazole and triazole are about 80–85% aromatic relative to benzene, through both magnetic and geometric criteria. Thiazole and oxazoles are found least aromatic where quantitative estimates of aromaticities are about 34–42%, relative to benzene. These quantitative estimates of aromaticities of five membered heterocycles are also comparable to those from aromatic stabilization energies. The quantification of aromaticity through energetic, magnetic, and structural criteria can deliver the similar inferences provided that suitable reference systems are chosen.

Effects of Aromatic Stabilization Energies on Photochromism of New Asymmetrical Azaindole-Containing Diarylethenes

2015 ◽  
Vol 33 (7) ◽  
pp. 785-791 ◽  
Author(s):  
Zhiyuan Sun ◽  
Congcong Zhang ◽  
Hui Li ◽  
Congbin Fan ◽  
Gang Liu ◽  
...  
Keyword(s):  
Stabilization Energies ◽  
Aromatic Stabilization

QSPR CALCULATION OF AROMATICITY IN SOME FIVE-MEMBERED HETEROAROMATIC COMPOUNDS

2004 ◽  
Vol 03 (02) ◽  
pp. 145-153 ◽  
Author(s):  
PABLO R. DUCHOWICZ ◽  
EDUARDO A. CASTRO
Keyword(s):  
Experimental Data ◽  
Magnetic Susceptibility ◽  
Molecular Descriptors ◽  
Chemical Shifts ◽  
Regression Equations ◽  
Linear Quadratic ◽  
Multilinear Regression ◽  
Heteroaromatic Compounds ◽  
Stabilization Energies ◽  
Aromatic Stabilization

Aromatic stabilization energies (ASE) for a set of 29 five-membered heteroaromatic compounds are calculated using molecular descriptors such as magnetic susceptibility exaltation (Λ), nucleus-independent chemical shifts (NICS), and electrotopological indices (EI) via linear, quadratic and cubic fitting polynomials. Theoretical estimations compare fairly well with experimental data when three variables multilinear regression equations are employed.

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