About this paper

Appears in:
Pages: 2482-2490
Publication year: 2014
ISBN: 978-84-617-0557-3
ISSN: 2340-1117

Conference name: 6th International Conference on Education and New Learning Technologies
Dates: 7-9 July, 2014
Location: Barcelona, Spain

ON THE SHORTCOMINGS OF THE RESONANCE MODEL TO DESCRIBE MOLECULAR ELECTRON DENSITY DISTRIBUTIONS AND THEIR EVOLUTIONS IN SIMPLE CHEMICAL PROCESSES

I. Perez-Juste, R. Mosquera, C. Bravo-Diaz

University of Vigo (SPAIN)
Simple, intuitive and easy to learn, the resonance model (RM) is still one of the most often employed tools for explaining mechanisms of chemical processes or predicting their products. Thus, chemistry students dedicate a significant amount of time to study this model, which is a topic included and worked with detail in Chemistry curricula. Nevertheless, several research groups have pointed out diverse evidences which seem to indicate the RM is not suitable for describing the evolution of the electron density in various simple chemical processes. Thus, reaction steps and even whole reaction mechanisms based upon it have be questioned. Moreover, some experimental facts like the evolution of pKas along certain series of organic compounds, cannot be explained by the RM. Conformational equilibria, protonations or hydride additions are examples of simple processes where the resonance model leads to explanations that contradict those obtained using modern quantum chemical methods for the electron density analysis. Among them, the discrepancies with the quantum theory of atoms in molecules (QTAIM) are particularly remarkable.

QTAIM can be considered as a very reliable method for electron density analysis, as it is based exclusively on the basic principles of Physics without introducing any other hypothesis. This work provides a quick overview on QTAIM and reviews part of contradictions between its results and RM interpretations, aiming to state simple messages to teach in the class room with clear examples based on firmly established results. To this end, several cases are selected in this work: rotational barrier of esters and amides, atomic charges of diazonium ions, distribution of electron density in flavylium cation, evolution of the electron density upon protonation, formation of hydrogen bonded adducts, and nucleophilic addition to carbonylic compounds.

@InProceedings{PEREZJUSTE2014ONS,
author = {Perez-Juste, I. and Mosquera, R. and Bravo-Diaz, C.},
title = {ON THE SHORTCOMINGS OF THE RESONANCE MODEL TO DESCRIBE MOLECULAR ELECTRON DENSITY DISTRIBUTIONS AND THEIR EVOLUTIONS IN SIMPLE CHEMICAL PROCESSES},
series = {6th International Conference on Education and New Learning Technologies},
booktitle = {EDULEARN14 Proceedings},
isbn = {978-84-617-0557-3},
issn = {2340-1117},
publisher = {IATED},
location = {Barcelona, Spain},
month = {7-9 July, 2014},
year = {2014},
pages = {2482-2490}}
TY - CONF
AU - I. Perez-Juste AU - R. Mosquera AU - C. Bravo-Diaz
TI - ON THE SHORTCOMINGS OF THE RESONANCE MODEL TO DESCRIBE MOLECULAR ELECTRON DENSITY DISTRIBUTIONS AND THEIR EVOLUTIONS IN SIMPLE CHEMICAL PROCESSES
SN - 978-84-617-0557-3/2340-1117
PY - 2014
Y1 - 7-9 July, 2014
CI - Barcelona, Spain
JO - 6th International Conference on Education and New Learning Technologies
JA - EDULEARN14 Proceedings
SP - 2482
EP - 2490
ER -
I. Perez-Juste, R. Mosquera, C. Bravo-Diaz (2014) ON THE SHORTCOMINGS OF THE RESONANCE MODEL TO DESCRIBE MOLECULAR ELECTRON DENSITY DISTRIBUTIONS AND THEIR EVOLUTIONS IN SIMPLE CHEMICAL PROCESSES, EDULEARN14 Proceedings, pp. 2482-2490.
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