A DFT study of glutaconaldehyde benzoyl ester: Molecular stability, structure and chemical reactivity

 

Etude DFT de l’ester benzoylé du glutacondialdéhyde: stabilité moléculaire, structure et reactivité chimique

 

A. Mostefai1*, A. Rahmouni1, S. Taleb2

1 Laboratoire de Modélisation et de Méthodes de Calculs-  Université de Saida,

B.P. 138, Cité En- Nasr-20002- Saida – Algérie

2 Laboratoire de Matériaux & Catalyse- Faculté des Sciences- Université Djillali LIABES, Site I, faubourg Ben M’Hidi,

W22000-Sidi Bel- Abbès, Algérie

* Corresponding author: E-mail: m_asma07@yahoo.fr

Received: 25 March 2011; revised version accepted: 12 July 2011

 

Abstract

   Almost all enol esters of glutaconaldehyde have been shown to have the thermodynamically stable all trans structure. It therefore appeared of interest to see, in the first part, if the assigned all-trans configuration for glutaconaldehyde benzoyl ester could be theoretically confirmed.  We were interested then in the relative stabilities of the possible isomeric structures of this ester which arise from the various possible configurations of the conjugated carbone-carbone double bonds. All isomers were fully optimized at DFT level of theory. The energies, relative energies of all possible isomers are given and discussed. Our calculations showed, as expected, that the all-trans specie with respect to other configurations is the most stable. The geometry of stable configuration was likewise studied; main geometric parameters of this molecule are then given and discussed, in the second part.  Because our main interest, in this work, was to predict which atomic site is the most susceptible to undergo either a nucleophilic or an electrophilic attack, it will be sufficient to focus attention to the calculated  reactivity indices derived from density functional theory which were used as an alternative to the traditional frontier orbital theory. Fukui functions (FF), local softness and local philicity were applied to probe the local reactivity and site selectivity. The dual descriptors were also shown in this study, not only to be capable of simultaneously explaining the nucleophilicity and electrophilicity of the given atomic sites, but especially to identify a dual atom which is proposed to act, simultaneously, as an electron acceptor and an electron donor in the molecule under investigation. The predictions thus made are in a good agreement with experimental results and  theoretical calculations of the previously studied analogues.

 

Keywords: Geometry optimization; reactivity; glutaconaldehyde benzoyl ester; Relative stability; ab inito; DFT; Fukui indices; local reactivity descriptors; HOMO; LUMO.

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