Non-covalent C–Cl…π interaction in acetylene-carbon tetrachloride adducts: Matrix isolation infrared and ab initio computational studies

Ab initio computational studies have been carried out for three molecules that are commonly classed as antiaromatic: cyclobutadiene (1), 1,3-diazacyclobutadiene (7), and 1,4-dihydropyrazine (6). Their dinitro and diamino derivatives were also investigated. Stabilizing or destabilizing energetic effects were quantified by means of the isodesmic reaction procedure at the MP2/6-31G*//HF/3-21G level, and calculated molecular electrostatic potentials (HF/STO-5G//HF/3-21G) were used as a probe of electron delocalization. Our results do not show extensive delocalization in the π systems of any one of the three parent molecules. The destabilization found for 1 and 7 is attributed primarily to strain and to repulsion between the localized π electrons in the C=C and C=N bonds, respectively. However, 6 is significantly stabilized, presumably due to limited delocalization of the nitrogen lone pairs. NH2 groups are highly stabilizing, apparently because of lone pair delocalization. NO2 is neither uniformly stabilizing nor destabilizing.

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Computational studies on carbohydrates: solvation studies on maltose and cyclomaltooligosaccharides (cyclodextrins) using a DFT/ab initio-derived empirical force field, AMB99C

Carbohydrate Research ◽

10.1016/s0008-6215(00)00043-4 ◽

2000 ◽

Vol 326 (3) ◽

pp. 210-226 ◽

Cited By ~ 55

Author(s):

Frank.A. Momany ◽

J.L. Willett

Keyword(s):

Force Field ◽

Ab Initio ◽

Computational Studies ◽

Empirical Force Field

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Structure and selective visible photodissociation of the O3:Br2 and O3:BrCl complexes: An infrared matrix isolation and ab initio study

Chemical Physics ◽

10.1016/s0301-0104(96)00375-8 ◽

1997 ◽

Vol 216 (1-2) ◽

pp. 105-118 ◽

Cited By ~ 15

Author(s):

M. Bahou ◽

L. Schriver-Mazzuoli ◽

A. Schriver ◽

P. Chaquin

Keyword(s):

Ab Initio ◽

Matrix Isolation ◽

Ab Initio Study

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Combined Matrix-Isolation Infrared and Theoretical DFT and ab Initio Study of the Nonionized Valine Conformers

The Journal of Physical Chemistry A ◽

10.1021/jp984457v ◽

1999 ◽

Vol 103 (22) ◽

pp. 4404-4412 ◽

Cited By ~ 80

Author(s):

S. G. Stepanian ◽

I. D. Reva ◽

E. D. Radchenko ◽

L. Adamowicz

Keyword(s):

Ab Initio ◽

Matrix Isolation ◽

Ab Initio Study ◽

Combined Matrix

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[3,3] Sigmatropic Rearrangement of Some Fluorinated 1,5-Hexadienes

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20021517 ◽

2002 ◽

Vol 67 (10) ◽

pp. 1517-1532 ◽

Cited By ~ 5

Author(s):

William R. Dolbier ◽

Keith W. Palmer ◽

Feng Tian ◽

Piotr Fiedorow ◽

Andrzej Zaganiaczyk ◽

...

Keyword(s):

Experimental Data ◽

Ab Initio ◽

Transition States ◽

Activation Parameters ◽

Sigmatropic Rearrangement ◽

Semiempirical Methods ◽

Cope Rearrangement ◽

Computational Studies ◽

Stepwise Mechanism ◽

Radical Intermediates

Fluorine atoms incorporated into 1,5-hexadiene molecule should influence the kinetic as well as the thermodynamic parameters of [3,3] sigmatropic rearrangement (Cope rearrangement). Within few decades is has been documented that this transformation proceeds in a concerted manner, rather than stepwise with some radical intermediates involved. Few new terminally fluorinated 1,5-hexadienes (compounds 3, 5A, 7, 9 and 5B) have been synthesized. The activation parameters of rearrangement have been determined and compared with those known for hydrocarbon analogues. While systems developing chair-like transition states (compounds 3 and 5) showed close similarity with hydrocarbon analogues (compound 1), those developing boat-like transition states (compounds 7, 9 and 5B) may proceed through radical stepwise mechanism. Computational studies of the transition states were carried out, showing that only ab initio methods (MP2 and especially DFT) can give approximate correlation with experimental data, whereas in the case of hydrocarbon analogues even simple semiempirical methods (AM1) were reliable enough to reproduce experimental results.

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