interaction types, irrespective of whether they have a name or have previously been
identified. Finally, we will show how this tool can be used to understand chemical
change along a chemical reaction. We will show an example of torquoselectivity
and put forward an explanation of selectivity based on secondary interactions which
is complementary to the historical orbital approach.
18.1 Introduction
As defined by Linus Pauling, “Chemistry is the science of substances: their
structure, their properties, and the reactions that change them into other substances”
[1]. The first aspects, structure and properties, are clearly associated with the
arrangement of atoms in a molecule, i.e. the chemical bond. These bonds determine
Pauling’s third aspect, chemical reactivity. In other words, chemical bonds are the
undisputed foundation of chemistry and their visualization should allow chemists to
understand how molecules behave at the most fundamental level.
Achievement of a mechanistic understanding of chemical and biological functions as well as the structure of solid materials depends on knowing the geometric
structure and the nature of bonds. But, despite the chemical bond being a fundamental concept in chemistry, “what is a chemical bond?” still remains a critical
question for the chemical community because of the lack of a unique definition as
well as an unclear understanding of its physical nature.
Successful numerical solution of the Schrödinger equation has yielded energies
and properties of atoms and molecules, but not yet a clear physical explanation of
chemical bonding. There is even a controversy on the mechanistic origin of the
most “simple” chemical bond, covalent bonding, as it was remarked by Burdett in
his classical book [2].
As recently as in 2007, a special issue was devoted to the “90 Years of Chemical
Bonding” [3]. In this issue, the chemical bond was compared to a unicorn, “a
mythical but useful creature, which brings law and order [···] in an otherwise
R. Chaudret
Scienomics, 16 rue de l’Arcade, 75008 Paris, France
e-mail: Robin.Chaudret@scienomics.com
M.-L. Bonnet
Institut de Recherche de Chimie Paris, ENSCP, Ecole Nationale Superieure de Chimie de
Paris Chimie ParisTech, UMR 8247, 75231 Paris, France
e-mail: marie-laure.bonnet@chimie-paristech.fr
M.-L. Bonnet
Institut de Recherche de Chimie Paris, CNRS, UMR 8247, 75231 Paris, France
R.A. Boto
Institut du Calcul et de la Simulation (ICS), Université Pierre et Marie Curie (UPMC), Paris
VI, 75005 Paris, France
492
C. Narth et al.
identified. Finally, we will show how this tool can be used to understand chemical
change along a chemical reaction. We will show an example of torquoselectivity
and put forward an explanation of selectivity based on secondary interactions which
is complementary to the historical orbital approach.
18.1 Introduction
As defined by Linus Pauling, “Chemistry is the science of substances: their
structure, their properties, and the reactions that change them into other substances”
[1]. The first aspects, structure and properties, are clearly associated with the
arrangement of atoms in a molecule, i.e. the chemical bond. These bonds determine
Pauling’s third aspect, chemical reactivity. In other words, chemical bonds are the
undisputed foundation of chemistry and their visualization should allow chemists to
understand how molecules behave at the most fundamental level.
Achievement of a mechanistic understanding of chemical and biological functions as well as the structure of solid materials depends on knowing the geometric
structure and the nature of bonds. But, despite the chemical bond being a fundamental concept in chemistry, “what is a chemical bond?” still remains a critical
question for the chemical community because of the lack of a unique definition as
well as an unclear understanding of its physical nature.
Successful numerical solution of the Schrödinger equation has yielded energies
and properties of atoms and molecules, but not yet a clear physical explanation of
chemical bonding. There is even a controversy on the mechanistic origin of the
most “simple” chemical bond, covalent bonding, as it was remarked by Burdett in
his classical book [2].
As recently as in 2007, a special issue was devoted to the “90 Years of Chemical
Bonding” [3]. In this issue, the chemical bond was compared to a unicorn, “a
mythical but useful creature, which brings law and order [···] in an otherwise
R. Chaudret
Scienomics, 16 rue de l’Arcade, 75008 Paris, France
e-mail: Robin.Chaudret@scienomics.com
M.-L. Bonnet
Institut de Recherche de Chimie Paris, ENSCP, Ecole Nationale Superieure de Chimie de
Paris Chimie ParisTech, UMR 8247, 75231 Paris, France
e-mail: marie-laure.bonnet@chimie-paristech.fr
M.-L. Bonnet
Institut de Recherche de Chimie Paris, CNRS, UMR 8247, 75231 Paris, France
R.A. Boto
Institut du Calcul et de la Simulation (ICS), Université Pierre et Marie Curie (UPMC), Paris
VI, 75005 Paris, France
492
C. Narth et al.