Azo-hydrazo conversion via [1,5]-hydrogen shifts. A combined experimental and theoretical study

Brasil, Edikarlos; Borges, Rosivaldo S.; Romero, Oscar A. S.; Alves, Cláudio Nahum; Sáez, José A.; Domingo, Luís R.

doi:10.1016/j.tet.2012.06.013

Cited by 6 publications

(3 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Analogue rationalizations have been recently exemplied in the exploration of polar chemical organic reactions. [54][55][56][57][58][59] In order to properly characterize the thermal decomposition process, in the following sections the progress of the reaction will be examined in terms of the electronic events governing the transformation evolving via the localized four-membered transition state.…”

Section: Computational Detailsmentioning

confidence: 99%

Understanding the thermal dehydrochlorination reaction of 1-chlorohexane. Revealing the driving bonding pattern at the planar catalytic reaction center

et al. 2015

View full text Add to dashboard Cite

The nature of bonding along the gas-phase thermal decomposition of 1-chlorohexane to produce 1-hexene and hydrogen chloride has been examined at the DFT M05-2X/6-311+G(d,p) level of theory. Based on results both from energetical and topological analysis of the electron localization function (ELF), we propose to rationalize the experimental available results not in terms of a decomposition via a four-membered cyclic transition structure (TS), but properly as a two stage one step reaction mechanism featuring a slightly asynchronous process associated to the catalytic planar reaction center at the TS. In this context, the first electronic stage corresponds to the ‫ܥ‬ ఋା ••• ‫݈ܥ‬ ఋି bond cleavage, which take place on the activation path earlier the transition structure be reached. There is no evidence of a Cl-C bond at the TS configuration. The second stage, associated to the top of the energy barrier, includes the TS and extends beyond on the deactivation pathway towards the products. The existence of both bonding and nonbonding non covalent interactions (NCI) are also revealed for the first time for the TS configuration. 17 47 to point -9 along the IRC reaction pathway. Arbitrarily the second stage concerning main electronic changes will be associated to points -9 to +9. Both stages refer to regions where key electronic changes driving the transformation take place. Note that from point -34 to point -5, the population associated to the disynaptic basin V(C α ,C β ) increases from 1.99e to 2.20e, whereas the population integrated in the disynaptic protonated basin V(H β ,C β ) decreases from 1.98e to 1.72e. The attractor corresponding to the forming double bond localizes out of the line connecting the carbon center cores. This topology for the C  -C  region remains unchanged until point 12 in region g. At the top of the energy barrier, within the entire interval IRC=(-0.97962,+0.97971), i.e., point -9 to point 9, we observe an isolated electron localization region integrating to 7.64e which is associated to the migrating chlorine center. This picture, on the top of the barrier, corresponds to a lonely chlorine atom bearing an electronic charge of -0.64 while evolving to the encounter of the H β center.Thereafter, within the tiny region d four valence monosynaptic basins V(Cl) associated to the negatively charged chlorine center adopt a tetrahedral conformation, with an increasing in the population from 7.64e to 7.70e. In this region the valence basins populations for V(C α ,C β ) and V(H β ,C β ) varies from 2.41e to 2.34e, and from 1.81e to 1.51e, respectively. The migrating chlorine center develops thus a maximum charge of -0.71 at the transition structure (point 0). ELF picture of bonding reveals that activation events are mainly associated to conformational changes in preparation of the reaction center (region a), followed by the breaking of the Cl-C α bond (regions b and c), and the start of the migration of H  atom with the associated bonding changes at C α -C β -H β moiety (regions c and d). Regarding t...

show abstract

Section: Computational Detailsmentioning

confidence: 99%

Understanding the thermal dehydrochlorination reaction of 1-chlorohexane. Revealing the driving bonding pattern at the planar catalytic reaction center

et al. 2015

View full text Add to dashboard Cite

show abstract

“…While these changes take place continuously along the intermolecular reactions I and V through the perpendicular approach of the two parallel ethylene frameworks, in the intramolecular reactions II , III and IV , this rehybridisation demands the twist of the terminal =CH 2 methylene groups in order to make the C‐to‐C coupling between the interacting pseudoradical centers favourable; and finally iv) in TS1 ‐ TS4 , the lengths of the C−C bonds, between 1.37 Å and 1.40 Å, are closer to those in benzene 1 , 1.38 Å. However, this similitude is a consequence of two different behaviours; while in benzene 1 the equalisation of the C−C bond lengths to 1.38 Å is a consequence of the maximum electronic delocalisation in this aromatic compound, the equalisation in the pseudocyclic TSs is a consequence of the bonding changes demanded for the C−C single bond formation, which usually takes place after passing the TSs …”

Section: Resultsmentioning

confidence: 98%

“…Herein, a topological analysis of ELF results concerning the TSs associated with five classical ( pericyclic ) organic reactions, namely: i) the DA reaction between butadiene 2 and ethylene 3 ; ii) the electrocyclic reaction of hexatriene 5 ; iii) the Cope or [3,3] sigmatropic rearrangement of 1,5‐hexadiene 7 ; iv) the 1,5‐hydrogen shift or [1,5] sigmatropic rearrangement of 1,3‐pentadiene 8 ; and v) the ene or Alder reaction between propene 9 and ethylene 3 is presented (see Scheme ). A further quantum theory of atoms in molecules (QTAIM) analysis at the interatomic regions of the TSs where ELF analysis does not indicate bonding electron density is also performed.…”

Section: Introductionmentioning

confidence: 99%

Aromaticity in Pericyclic Transition State Structures? A Critical Rationalisation Based on the Topological Analysis of Electron Density

et al. 2016

Self Cite

View full text Add to dashboard Cite

The nature of the electron delocalisation pattern within a cyclic structure, i. e. the aromatic character, is examined for sixmembered pseudocyclic transition state structures (TSs) involved in five representative examples of so-called pericyclic reactions. Results of the electron localisation function (ELF) and the quantum theory of atoms in molecules (QTAIM) analyses of the electron density evidence that in four of the cases, at least one pair of atoms are not bound at the TS configuration, thus precluding a possible cyclic conjugation. These findings make it possible to rule out the aromatic character of these TSs. High values of the synchronicity Sy index at the TSs contrast with the bonding changes evidenced by ELF topological analysis. The magnitude of the nucleus independent chemical shift (NICS) computed for the five TSs becomes much more negative than that of the reference system, benzene, with no obvious relation to the strong evidence of the pattern of delocalisation revealed by the topological analysis of ELF and QTAIM for each TS. The topology of the anisotropy of current induced density (ACID) at each TS reveals the actual existence of strong nonsymmetrical patterns of electron delocalisation of the five TSs.[a] Prof.

show abstract

Solvent polarity sensitive characteristics of various tautomers of azo compounds: Linear and nonlinear optical properties

Sadigh

Zakerhamidi

2020

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

View full text Add to dashboard Cite

Azo-hydrazo conversion via [1,5]-hydrogen shifts. A combined experimental and theoretical study

Cited by 6 publications

References 28 publications

Understanding the thermal dehydrochlorination reaction of 1-chlorohexane. Revealing the driving bonding pattern at the planar catalytic reaction center

Understanding the thermal dehydrochlorination reaction of 1-chlorohexane. Revealing the driving bonding pattern at the planar catalytic reaction center

Aromaticity in Pericyclic Transition State Structures? A Critical Rationalisation Based on the Topological Analysis of Electron Density

Solvent polarity sensitive characteristics of various tautomers of azo compounds: Linear and nonlinear optical properties

Contact Info

Product

Resources

About