DFT Study of the Cyclization of 1,2-divinylbenzene snd Derivatives

The 10th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryElectrocyclization reactions of 1,2-divinylbenzene and several related molecules were studied by performing density functional theory (DFT) calculations together with the 6-31+G* basis set. Reactants, products, and transition states for each reaction were localized and the IRC connecting reactants and products was also obtained. Magnetic properties were evaluated along the reaction path to elucidate the characteristics of the reactions studied with respect to their aromaticity and pericyclic character. Though reactions B and C seem to be borderline cases between pericyclic andpseudopericyclic behaviour, the analysis of different magnetic properties allow us to conclude that all reactions studied are pericycli

The influence of BF3 on the reaction path of the [4 + 2] cycloaddition of vinylketene with formaldimine. A computational study

The 10th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryA comprehensive B3LYP/6-31+G* study of the influence of BF3 on the [4 + 2] cycloaddition of vinylketene with formaldimine was conducted. For this purpose, the complete pathway was determined and changes in different magnetic properties (magnetic susceptibility, χ, magnetic susceptibility anisotropy, χanis, and the nucleus-independent chemical shifts, NICS) were monitored along the reaction profile with a view to estimating the aromatization associated to the process. We have also applied the ACID (anisotropy of the current-induced density) method with the same intention

Theoretical study of the pericyclic/pseudopericyclic character of the automerization of Perfluorotetramethyl (Dewar thiophene) exo-S-oxide

The 10th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryA theoretical study of the "walk" rearrangement in bicyclo[2.1.0]pentene and perfluorotetramethyl (Dewar thiophene) exo-S-oxide has been carried out. In order to analyze the pericyclic character of these two reactions, some magnetic properties (NICS and ACID) have been calculated in the reactant/product and in the transition state of each reaction. Despite the differences between them, the results for both reactions show an enhancement of aromaticity in the transition state, which is consistent with a pericyclic behavior. NBO calculations show that the small activation energy for the second reaction can be interpreted in terms of a strongly stabilization of the transition state by the exo-oxide substituent. No evidence of any pseudopericyclic character has been found. Although the walk rearrangement in erfluorotetramethyl (Dewar thiophene) exo-S-oxide has special characteristics, the process of [1,3]-sigmatropic shift remains with a fundamental role in its mechanism. So, the mechanism proposed by Lemal et al, should be revise

On the Mechanism of Rhodium-Catalyzed [6+2] Cycloaddition of 2-Vinylcylobutanones and Alknenes

The 11th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryThe intramolecular [6+2] cycloaddition mechanism of 2­vinylcyclobutanones and alkenes catalyzed by the [Rh(CO)2Cl]2 dimer has been studied using density functional theory, comparing this multistep process with the one­step reaction in absence of catalyst. This possible mechanism agrees with what was previously experimentally suggested. Calculations have also allowed to explain the selectivity of the reactio

A computational study of the mechanism of the unimolecular elimination of α, β - unsaturated aldehydes in the gas phase

The 13th International Electronic Conference on Synthetic Organic Chemistry session Computational Chemistr

A theoretical study of the aromatic character of polyphosphaphospholes. Is the pyramidality the only factor to take into consideration?

The 13th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryA comprehensive MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) study of the aromatic character of phospholes, Pn(CH)4-nPH with n = 0-4 was conducted. For this purpose, the structures for these compounds were optimized at both theoretical levels and different magnetic properties (magnetic susceptibility, χ, magnetic susceptibility anisotropy, χanis, and the nucleus-independent chemical shifts, NICS) were evaluated. For comparison, these magnetic properties were also calculated in the optimized structures with planarity constraints. We have also applied the ACID (anisotropy of the current-induced density) method in this analysis. The main conclusions are the aromatic character of these compounds, the relationship between aromaticity and planarity and the importance of other factors in this aromaticit

Study of the Interaction between Aniline and CH3CN, CH3Cl and CH3F

The 12th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryA computational study of dimers formed by aniline and one CH3X molecule, X being CN, Cl or F, was carried out to elucidate the main characteristics of the interacting systems. Two different structures were found for each of the dimers, depending on the relative location of the CH3X molecule with respect to the amino hydrogen atoms. The most stable minimum for both acetonitrile and methyl chloride corresponds to structures where the CH3X molecule is located with its methyl group over the aromatic ring establishing a C-H···p contact and simultaneously interacting with the amino group with a N-H···X contact. In methyl fluoride complex, however, no significant interaction takes place with the aromatic ring in the most stable structure. In this case, the interaction takes places with the amino group forming a five member cycle with N-H···F and C-H···N contacts. As regards interaction energies, the stronger complex is formed with acetonitrile, with an interaction energy amounting to -6.4 kcal/mol. Methyl chloride and methyl fluoride form complexes with interaction energies amounting to -4.1 and -4.2 kcal/mol, respectively, though the structural arrangements are quite different for both structures. The results of the SAPT(DFT) analysis indicate that in most complexes the leading contribution to the stabilization of the complex is dispersion, though the electrostatic contribution is almost as important. However, in methyl fluoride most stable complex the larger attractive term is of electrostatic natur

Characteristics of the interaction in azulene···(H2X)n=1,2(X=O,S) clusters

The 11th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryA computational study of clusters containing azulene and up to two molecules of water or hydrogen sulfide was carried out to elucidate the main characteristics of these X-H···π interacting systems. For clusters with one H2X molecule only one structure was found interacting with the aromatic cloud of azulene, with an interaction energy of -3.1 kcal/mol both for H2O and H2S as calculated at the CCSD(T)/AVDZ level. On the other hand, MP2 overestimates the interaction in hydrogen sulfide clusters, whereas the MPWB1K functional produces values in very good agreement with CCSD(T). A variety of structures were located for clusters with two H2X molecules. The most stable ones are those which simultaneously present hydrogen bond between H2X molecules and X-H···π contacts. Also, only this kind of structure presents relevant three body stabilizing contributions. On the other hand, the interaction of azulene with (H2X)2 dimer is stronger precisely for structures which do not present X-H···X hydrogen bond. This suggest that for larger systems, structures with the molecules distributed over the aromatic surface but without interacting among them, can be competitive with other, hydrogen bonded clusters, especially in H2S containing system

Study of the Lithium Cation-Ferrocene Interaction by DFT Calculations: an In-Depth Analysis of the Existence of a Planetary System

The 12th International Electronic Conference on Synthetic Organic Chemistry session Computational Chemistr