Giovanni Villani

The concept of molecular structure is one of the most important concepts of chemistry. In fact, molecular structure is closely related to the concept of chemical substance and its set of properties, and it is the main factor in the explanation of reactivity. In fact, much of the behavior of substances is explained in terms of the structure of their component molecules. This may explain why people tend to take the notion of molecular structure for granted. However, the problem begins already when it comes to specifying the concept, since there is no clear definition of ‘molecular structure’ valid for all chemistry. The purpose of the present article is to show that the term ‘molecular structure’ subsumes very different notions, which depend on how the molecule and its components are conceived, and each of which brings its own difficulties. In particular, we will focus on how the molecule and its structure are devised from a classical view and from a quantum–mechanical view, and will discuss the different problems related with molecular structure that arise in each case.

The fundamental concept of structured chemical system has been introduced and analysed in this paper. This concept, as in biology but not in physics, is very important in chemistry. In fact, the main chemical concepts (molecule and compound) have been identified as systemic concepts and their use in chemical explanation can only be justified in this approach. The fundamental concept of “environment” has been considered and then the system concept in mechanics, chemistry and biology. The differences and the analogies between the use of the systemic approach in these disciplines have been analyzed and correlated to the general problem of reductionism and complexity perspectives. The inanimate–animate dichotomy can be reconsidered in this new approach. Since the chemical systemic concepts of molecule and compound can be dated to the nineteenth century, chemistry can be considered the first true systemic science and its historical evolution can be a model for other sciences (such as the humanities) where the systemic concepts are important

“La vita non è altro che chimica” e “la vita non è riducibile a chimica” sono due idee opposte dello storico problema di identificare la specificità del vivente. Sebbene siano due posizioni opposte, per entrambe la chimica è un punto di riferimento per “leggere” il vivente, è la prospettiva privilegiata in cui “interpretare” il vivente. La prospettiva di questo libro non è quella riduzionista, ma quella sistemica delle relazioni. La vita, come le altre proprietà emergenti, non si esaurisce nelle relazioni con l’interno (le sostanze chimiche costituenti) e con l’esterno (l’ambiente), ma senza di esse non è studiabile scientificamente. Il linguaggio chimico, infatti, è il linguaggio universale della materia, sia di quella che costituisce le rocce sia di quella degli organismi viventi e, parafrasando Galileo, la materia dell’universo è scritta in linguaggio chimico e i suoi caratteri sono atomi, molecole e macromolecole; senza queste conoscenze è un aggirarsi vanamente per un oscuro labirinto.

The concepts of living and non-living have changed in time, from the ancient Greeks to the present day and the specificity of living or has been associated with a particular matter, active such as the chemical one, or was considered as a product of the spatial organization of a passive matter. The chemical approach to living, along the path from biological chemistry to biochemistry and, finally, to molecular biology, tried to relate these two aspects. Today, these two views of living can be merged in chemistry perspective that takes account of the general reflections on the complexity and the systemic, with a perspective of "systemic complexity".

The present work is a comment of a recent paper by Fortin and coauthors in which the authors propose the introduction of Bohmian mechanics in the philosophy of chemistry and the use of standard quantum mechanics as a mere instrument of prediction. This way would allow overcoming the obstacles found in linking molecular chemistry and quantum mechanics. Starting from some remarks on the orbital concept, we highlight and discuss some general issues that need to be taken into account when two scientific theories coexist within the same investigation field, i.e. SQM and BM.