The Origin of Cis Effect in 1,2-Dihaloethenes: The Quantitative Comparison of Electron Delocalizations and Steric Exchange Repulsions

Yamamoto, Takashi; Kaneno, Daisuke; Tomoda, Shuji

doi:10.1246/bcsj.81.1415

Cited by 30 publications

(39 citation statements)

References 50 publications

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“…is overwhelmingly enhanced by 401.44 kJ/mol from the n 2N10 →n* H12 interaction. It is worth noting that the 2-HPY tautomer is mostly stabilized by the π→π* interactions while the stability of 2-PY is mostly enhanced by the n→σ* or n→π* interactions; called the lone-par effect [50]. In addition, the very high charge transfer interactions n 2O11 →n* 1H12 and n 1N10 →n* 1H12 that yielded 284.44 and 401.44 kJ/mol for the stability of T.S., respectively, drove the debilitation of the O 11 H 12 and N 10 H 12 bonds and hence expediting the transport of the proton from O 11 to N 11 and vice-versa; through a 1,3-proton shift [41] mechanism.…”

Section: Resultsmentioning

confidence: 99%

The Thermodynamic and Kinetic Properties of 2-Hydroxypyridine/2-Pyridone Tautomerization: A Theoretical and Computational Revisit

Hejazi

Osman

Al‐Youbi

et al. 2016

IJMS

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The gas-phase thermal tautomerization reaction between 2-hydroxypyridine (2-HPY) and 2-pyridone (2-PY) was investigated by applying 6-311++G** and aug-cc-pvdz basis sets incorporated into some density functional theory (DFT) and coupled cluster with singles and doubles (CCSD) methods. The geometrical structures, dipole moments, HOMO-LUMO energy gaps, total hyperpolarizability, kinetics and thermodynamics functions were monitored against the effects of the corrections imposed on these functionals. The small experimental energy difference between the two tautomers of 3.23 kJ/mol; was a real test of the accuracy of the applied levels of theory. M062X and CCSD methods predicted the preference of 2-HPY over 2-PY by 5–9 kJ/mol; while B3LYP functional favoured 2-PY by 1–3 kJ/mol. The CAM-B3LYP and ωB97XD functionals yielded mixed results depending on the basis set used. The source of preference of 2-HPY is the minimal steric hindrance and electrostatic repulsion that subdued the huge hyperconjugation in 2-PY. A 1,3-proton shift intramolecular gas-phase tautomerization yielded a high average activation of 137.152 kJ/mol; while the intermolecular mixed dimer interconversion gave an average barrier height of 30.844 kJ/mol. These findings are boosted by a natural bond orbital (NBO) technique. The low total hyperpolarizabilities of both tautomers mark out their poor nonlinear optical (NLO) behaviour. The enhancement of the total hyperpolarizability of 2-HPY over that of 2-PY is interpreted by the bond length alternation.

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Section: Resultsmentioning

confidence: 99%

The Thermodynamic and Kinetic Properties of 2-Hydroxypyridine/2-Pyridone Tautomerization: A Theoretical and Computational Revisit

Hejazi

Osman

Al‐Youbi

et al. 2016

IJMS

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“…These interactions gave total delocalization energies of 45.09 and 44.36 kcal/mol for the eclipsed and bisected conformers, respectively. Thus the LP Effect [20] favored the eclipsed form by 0.73 kcal/mol. The total energies of the vicinal CH–CO* and CH–CH* interactions are 20.26 and 17.56 kcal/mol for the eclipsed and bisected conformers, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…This outcome can be explained in terms of the C1–H2 and C2–H4 anti arrangement. This kind of geometrical environment allows greater overlap between the interacting orbitals [20]. In contrast, the bisected form C1–H2 and C2–O1 bonds have less favorable overlap between their interacting orbitals.…”

Section: Resultsmentioning

confidence: 99%

Eclipsed Acetaldehyde as a Precursor for Producing Vinyl Alcohol

Osman¹,

Al‐Youbi²,

Elroby³

et al. 2012

IJMS

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The MP2 and DFT/B3LYP methods at 6-311++G(d,p) and aug-cc-pdz basis sets have been used to probe the origin of relative stability preference for eclipsed acetaldehyde over its bisected counterpart. A relative energy stability range of 1.02 to 1.20 kcal/mol, in favor of the eclipsed conformer, was found and discussed. An NBO study at these chemistry levels complemented these findings and assigned the eclipsed acetaldehyde preference mainly to the vicinal antiperiplanar hyperconjugative interactions. The tautomeric interconversion between the more stable eclipsed acetaldehyde and vinyl alcohol has been achieved through a four-membered ring transition state (TS). The obtained barrier heights and relative stabilities of eclipsed acetaldehyde and the two conformers of vinyl alchol at these model chemistries have been estimated and discussed.

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“…There is “ cis ‐effect,” a phenomenon in which the cis ‐isomer, due to specific intramolecular interactions, is more stable than the corresponding trans ‐isomer or has almost the same stability in some molecules with double bonds, as, for example, in 1,2‐dihaloethenes 32, or in indolylpyridylethene 33. However, in the case of the diarylethylenes studied, obviously, the grater stability of the cis ‐isomers relative to the trans ‐isomers is a result of drawbacks of parameterization of PM6 and RM1 semiempirical methods.…”

Section: Resultsmentioning

confidence: 99%

Comparative semiempirical and DFT study of styrylnaphthalenes and styrylquinolines and their photocyclization products

Будыка

Oshkin

2010

Int J of Quantum Chemistry

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Semiempirical molecular orbital (PM3, PM6, and RM1) and density functional theory (DFT) (B3LYP/6-31G*) studies are carried out for 1-and 2-styrylnaphthalenes and their aza-derivatives-2-and 4-styrylquinolines. Relative stabilities of three isomeric forms: E-and Z-isomers and the closed-ring dihydrocyclophotoproduct (derivative of dihydrophenanthrene) are calculated. Compared to PM3, PM6 and especially RM1 understate heats of formation; in some cases, PM6 and RM1 even place Z-isomer in energy below E-isomer. PM3 rather close to DFT predicts heats of isomerization reaction, whereas PM6 and especially RM1 underestimate these values. Semiempirical methods in comparison with DFT markedly underestimate heats of cyclization reaction; however, reproduce trends in relative stabilities of different isomers in dependence on the structure of styrylnaphthalenes and styrylquinolines. Qualitative correlation is found between calculated relative stabilities of the closed-ring forms (heats of cyclization reaction) and experimental data: cyclized products with low heats of cyclization are observed in steady-state photolysis and those with high heats of cyclization are not. In the latter case, the closed-ring compounds, if formed in the excited state, due to thermal instability decompose rapidly with ring opening in the ground state that prevents their observation.

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The Origin of Cis Effect in 1,2-Dihaloethenes: The Quantitative Comparison of Electron Delocalizations and Steric Exchange Repulsions

Cited by 30 publications

References 50 publications

The Thermodynamic and Kinetic Properties of 2-Hydroxypyridine/2-Pyridone Tautomerization: A Theoretical and Computational Revisit

The Thermodynamic and Kinetic Properties of 2-Hydroxypyridine/2-Pyridone Tautomerization: A Theoretical and Computational Revisit

Eclipsed Acetaldehyde as a Precursor for Producing Vinyl Alcohol

Comparative semiempirical and DFT study of styrylnaphthalenes and styrylquinolines and their photocyclization products

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