Theoretical study of the internal rotational barriers in some N-substituted nitropyrroles

The barrier to internal rotation around the central C2–C3 single bond of a series of (1E)-monosubstituted 1,3-butadienes and (1E,3E)-1-Y-4-X-disubstituted butadienes, with Y=NH2 or OCH3 and X=NO2, CHO, COOH, CN, CF3, Cl or F, were studied at the density functional w B97X-D/6-31G∗∗ level. The effect of substituents on π-conjugation in disubstituted 1,3-butadienes was studied by correlating the calculated internal rotational barriers with the difference in structural, atomic and molecular properties between the transition state TS and the s-trans conformers. The calculated differences in lengths of C–C, C–NH2 and C–OCH3 single bonds, N-H-N, and C-O-CH3 angles, NH2 out-of-plane angle, natural charges on amino nitrogen and methoxy oxygen, and the maximum electrostatic potential on amino hydrogens, were found to correlate strongly with the rotational barriers. The conjugative interaction was strongly stabilized in the case of strong π-electron acceptors such as NO2 or CHO and is slightly or negligibly affected with Cl and F groups. The resonance stabilization with the remaining acceptors decreases in the order COOH > CN > CF3. Acceptors X maintain their relative order of stabilization for the two donors, and NH2 is more stabilizing. Dominant resonance structures are suggested for highly and negligibly conjugated systems.

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Theoretical study of the internal rotational barriers of fluorine, chlorine, bromine, and iodine-substituted ethanes

Computational and Theoretical Chemistry ◽

10.1016/j.comptc.2019.112589 ◽

2019 ◽

Vol 1166 ◽

pp. 112589

Author(s):

Sílvio Quintino de Aguiar Filho ◽

Adão Marcos Ferreira Costa ◽

Igor Hernandes Santos Ribeiro ◽

Rogério Custodio ◽

Douglas Henrique Pereira

Keyword(s):

Theoretical Study ◽

Rotational Barriers ◽

Internal Rotational Barriers

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Theoretical study of internal rotational barriers of electrons donating and electrons withdrawing groups in aromatic compounds

Heliyon ◽

10.1016/j.heliyon.2020.e04957 ◽

2020 ◽

Vol 6 (9) ◽

pp. e04957

Author(s):

Daniel Rodrigues Lima ◽

Sílvio Quintino de Aguiar Filho ◽

Laura Beatriz Camargo do Oh ◽

Anna Karla dos Santos Pereira ◽

Douglas Henrique Pereira

Keyword(s):

Aromatic Compounds ◽

Theoretical Study ◽

Rotational Barriers ◽

Internal Rotational Barriers

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Theoretical study on the molecular structures of toluene, para-fluorotoluene, para-chlorotoluene, and 4-methylpyridine and their sixfold internal rotational barriers

International Journal of Quantum Chemistry ◽

10.1002/(sici)1097-461x(2000)77:4<772::aid-qua8>3.0.co;2-6 ◽

2000 ◽

Vol 77 (4) ◽

pp. 772-778 ◽

Cited By ~ 7

Author(s):

P. C. Chen ◽

F. M. Chang

Keyword(s):

Theoretical Study ◽

Molecular Structures ◽

Rotational Barriers ◽

Internal Rotational Barriers

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Theoretical study of the internal rotational barriers in nitrobenzene, 2-nitrotoluene, 2-nitrophenol, and 2-nitroaniline

International Journal of Quantum Chemistry ◽

10.1002/qua.1069 ◽

2001 ◽

Vol 83 (6) ◽

pp. 332-337 ◽

Cited By ~ 23

Author(s):

P. C. Chen ◽

S. C. Chen

Keyword(s):

Theoretical Study ◽

Rotational Barriers ◽

Internal Rotational Barriers

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Structural Parameters and Internal Rotational Barriers of tert-Butylammonium Ion: AM1 and ab initio Calculations

Zeitschrift für Naturforschung A ◽

10.1515/zna-1992-1215 ◽

1992 ◽

Vol 47 (12) ◽

pp. 1255-1256

Author(s):

Hiroyuki Ishida ◽

Yoshihiro Kubozono ◽

Setsuo Kashino ◽

Ryuichi Ikeda

Keyword(s):

Ab Initio Calculations ◽

Ab Initio ◽

Internal Rotation ◽

Barrier Height ◽

Structural Parameters ◽

Mo Calculations ◽

Ab Initio Mo Calculations ◽

Rotational Barriers ◽

Ab Initio Mo ◽

Internal Rotational Barriers

Semiempirical and ab initio MO calculations were performed to estimate the structural parameters of tert-butylammonium ion and its potential energies for the internal rotation of the CH3 and NH3+ groups. The barrier height for the rotation of NH3+ was found to be lower than for that of CH3 , corresponding to the C - N bond being longer than the C - C bond.

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