Quantitative Structure–Property Relationship (QSPR) Models for a Local Quantum Descriptor: Investigation of the 4- and 3-Substituted-Cinnamic Acid Esterification

Molecules

Cláudio E. Rodrigues-Santos³  Aurea Echevarria³  Carlos M. R. Sant𠆚nna³  Thiago B. Bitencourt²  Maria G. Nascimento¹  Glauco F. Bauerfeldt³ 

[1] Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis-SC 88040-900, Brazil; E-Mail:;Departamento de Engenharia de Alimentos, Universidade Federal da Fronteira Sul, Laranjeiras do Sul-PR 85303-775, Brazil; E-Mail:;Departamento de Química, Instituto de Ciências Exatas, Universidade Federal Rural do Rio de Janeiro-RJ, Seropédica 23890-900, Brazil; E-Mails:

关键词: O-protonation;    cinnamic acid;    FERMO;    Fukui functions;   

DOI  :  10.3390/molecules200917493

来源: mdpi

【 摘 要 】

In this work, the theoretical description of the 4- and 3-substituted-cinnamic acid esterification with different electron donating and electron withdrawing groups was performed at the B3LYP and M06-2X levels, as a two-step process: the O-protonation and the nucleophile attack by ethanol. In parallel, an experimental work devoted to the synthesis and characterization of the substituted-cinnamate esters has also been performed. In order to quantify the substituents effects, quantitative structure–property relationship (QSPR) models based on the atomic charges, Fukui functions and the Frontier Effective-for-Reaction Molecular Orbitals (FERMO) energies were investigated. In fact, the Fukui functions, ƒ⁺C and ƒ⁻O, indicated poor correlations for each individual step, and in contrast with the general literature, the O-protonation step is affected both by the FERMO energies and the O-charges of the carbonyl group. Since the process was shown to not be totally described by either charge- or frontier-orbitals, it is proposed to be frontier-charge-miscere controlled. Moreover, the observed trend for the experimental reaction yields suggests that the electron withdrawing groups favor the reaction and the same was observed for Step 2, which can thus be pointed out as the determining step.

【 授权许可】

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