How Chemistry and Physics Meet in the Solid State

To make sense of the marvelous electronic properties of the solid state, chemists must learn the language of solid-state physics, of band structures. An attempt is made here to demystify that language, drawing explicit parallels to well-known concepts in theoretical chemistry To the joint search of physicists and chemists for understanding of the bonding in extended systems, the chemist brings a great deal of intuition and some simple but powerful notions. Most important among these is the idea of a bond, and the use of frontier-orbital arguments. How to find localized bonds among all those maximally delocalized bands? Interpretative constructs, such as the density of states, the decomposition of these densities, and crystal orbital overlap populations, allow a recovery of bonds, a finding of the frontier orbitals that control structure and reactivity in extended systems as well as discrete molecules.     

Is there a quantum definition of a molecule?

The paper surveys how chemistry has developed over the past two centuries starting from Lavoisier’s classification of the chemical elements at the end of the eighteenth century; the subsequent development of the atomic–molecular model of matter preoccupied chemists throughout the nineteenth century, while the results of the application of quantum theory to the molecular model has been the story of this century. Whereas physical chemistry originated in the nineteenth century with the measurement of the physical properties of groups of chemical compounds that chemists identified as families, the goal of chemical physics is the explanation of the facts of chemistry in terms of the principles and theories of physics. Chemical physics as such was only possible after the discovery of the quantum theory in the 1920’s. By then the first of the sub‐atomic particles had been discovered and seemingly it is no longer possible to discuss chemical facts purely in terms of atoms and molecules – one has to recognize the electron and the nucleus, the parts of atoms. The combination of classical molecular structure with the quantum properties of the electron has given us a tremendously successful account of chemistry called ‘quantum chemistry’. Yet from the perspective of the quantum theory the deepest part of chemistry, the existence of chemical isomers and the very idea of molecular structure that rationalizes it, remains a central problem for chemical physics. This revised version was published online in July 2006 with corrections to the Cover Date.     

Objects of inquiry in classical chemistry: material substances

I argue in the paper that classical chemistry is a science predominantly concerned with material substances, both useful materials and pure chemical substances restricted to scientific laboratory studies. The central epistemological and methodological status of material substances corresponds with the material productivity of classical chemistry and its way of producing experimental traces. I further argue that chemist??s ??pure substances?? have a history, conceptually and materially, and I follow their conceptual history from the Paracelsian concept of purity to the modern concept of pure stoichiometric compounds. The history of the concept of ??pure substances?? shows that modern chemists?? concept of purity abstracted from usefulness rather than being opposed to it. Thus modern chemists?? interest in pure chemical substances does not presuppose a concept of pure science.     

Emergence in Chemistry: Chemistry as the Embodiment of Emergence

The main aim of the paper is to reinforce the notion that emergence is a basic characteristic of the molecular sciences in general and chemistry in particular. Although this point is well accepted, even in the primary reference on emergence, the keyword emergence is rarely utilized by chemists and molecular biologists and chemistry textbooks for undergraduates. The possible reasons for this situation are discussed. The paper first re-introduces the concept of emergence based on very simple geometrical forms; and considers some simple chemical examples among low and high molecular weight compounds. On the basis of these chemical examples, a few interesting philosophical issues inherent to the field of emergence are discussed – again making the point that such examples, given their clarity and simplicity, permit one to better understand the complex philosophical issues. Thus, the question of predictability is discussed, namely whether and to what extent can emergent properties be predicted on the basis of the component’s properties; or the question of the explicability (a top down process). The relation between reductionism and emergentism is also discussed as well as the notion of downward causality and double causality (macrodeterminism); namely the question whether and to what extent the emergent properties of the higher hierarchic level affect the properties of the lower level components. Finally, the question is analyzed, whether life can be considered as an emergent property. More generally, the final point is made, that the re-introduction of the notion of emergence in chemistry, and in particular in the teaching, may bring about a deeper understanding of the meaning of chemical complexity and may bring chemistry closer to the humanistic areas of philosophy and epistemology. This revised version was published online in July 2006 with corrections to the Cover Date.     

A neglected aspect of the puzzle of chemical structure: how history helps

Intra-molecular connectivity (that is, chemical structure) does not emerge from computations based on fundamental quantum-mechanical principles. In order to compute molecular electronic energies (of C₃H₄ hydrocarbons, for instance) quantum chemists must insert intra-molecular connectivity “by hand.” Some take this as an indication that chemistry cannot be reduced to physics: others consider it as evidence that quantum chemistry needs new logical foundations. Such discussions are generally synchronic rather than diachronic—that is, they neglect ‘historical’ aspects. However, systems of interest to chemists generally are metastable. In many cases chemical systems of a given elemental composition may exist in any one of several different metastable states depending on the history of the system. Molecular structure generally depends on contingent historical circumstances of synthesis and separation, rather than solely or mainly on relative energies of alternative stable states, those energies in turn determined by relationships among components. Chemical structure is usually ‘kinetically-determined’ rather than ‘thermodynamically-determined.’ For instance, cyclical hydrocarbon ring-systems (as in cyclopropene) are produced only in special circumstances. Adequate theoretical treatments must take account of the persistent effects of such contingent historical events whenever they are relevant—as they generally are in chemistry.     

Connecting the philosophy of chemistry,green chemistry,and moral philosophy

This paper aims to connect philosophy of chemistry, green chemistry, and moral philosophy. We first characterize chemistry by underlining how chemists: (1) co-define chemical bodies, operations, and transformations; (2) always refer to active and context-sensitive bodies to explain the reactions under study; and (3) develop strategies that require and intertwine with a molecular whole, its parts, and the surroundings at the same time within an explanation. We will then point out how green chemists are transforming their current activities in order to act upon the world without jeopardizing life. This part will allow us to highlight that green chemistry follows the three aforementioned characteristics while including the world as a partner, as well as biodegradability and sustainability concerns, into chemical practices. In the third part of this paper, we will show how moral philosophy can help green chemists: (1) identify the consequentialist assumptions that ground their reasoning; and (2) widen the scope of their ethical considerations by integrating the notion of care and that of vulnerability into their arguments. In the fourth part of the paper, we will emphasize how, in return, this investigation could help philosophers querying consequentialism as soon as the consequences of chemical activities over the world are taken into account. Furthermore, we will point out how the philosophy of chemistry provides philosophers with new arguments concerning the key debate about the ‘intrinsic value’ of life, ecosystems and the Earth, in environmental ethics. To conclude, we will highlight how mesology, that is to say the study of ‘milieux’, and the concept of ‘ecumeme’ proposed by the philosopher and geographer Augustin Berque, could become important both for green chemists and moral philosophers in order to investigate our relationships with the Earth.     

Polymer blends - current state of progress and future developments from an industrial viewpoint

Technical and economic considerations have given polymer blends a major share in the increasing sales of plastics. This applies both to general-purpose and to the higher value-added materials. Thus it is scarcely surprising that almost all polymer manufacturers have now developed comprehensive ranges of blends having particular property profiles. The principal types of blends currently available are described. The variety of products already developed should not be allowed to obscure the fact that certain conceivable and highly attractive property combinations have not so far been realized. If progress is to be made in this area, interdisciplinary cooperation between chemists and physicists in the fields of polymer chemistry, polymer physics and materials science is essential.     

From the Periphery: the genesis of Eugene P. Wigner's application of group theory to quantum mechanics

This paper traces the origins of Eugene Wigner's pioneering application of group theory to quantum physics to his early work in chemistry and crystallography. In the early 1920s, crystallography was the only discipline in which symmetry groups were routinely used. Wigner's early training in chemistry, and his work in crystallography with Herman Mark and Karl Weissenberg at the Kaiser Wilhelm institute for fiber research in Berlin exposed him to conceptual tools which were absent from the pedagogy available to physicists for many years to come. This both enabled and pushed him to apply the group theoretic approach to quantum physics. It took many years for the approach first introduced by Wigner in the 1920s – and whose reception by the physicists was initially problematical – to assume the pivotal place it now holds in physical theory and education. This is but one example that attests to the historic contribution made by the periphery in initiating new types of thought-perspectives and scientific careers.     

Studies to link the basic radiation physics and chemistry of liquid water

Collaborative work between radiation physicists and chemists is described, leading to a Monte Carlo model of the detailed events that occur when ionizing radiation interacts with water in the liquid state. The model treats explicitly the initial physical changes produced by radiation, the formation of chemically active species, and the subsequent diffusion-controlled chemical reactions that take place along the path of a charged particle. Several examples of calculated tracks and chemical yields are presented. The calculated time decay of the hydrated electron and OH radical are in good agreement with measurements from electron pulse radiolysis. The effect of dissolved oxygen on the computed chemical yields is presented. While many uncertainties necessarily exist in such an endeavor, the basic model linking the physics and chemistry of irradiated water appears to be consistent with existing experimental and theoretical data.     

Explanation and theory formation in quantum chemistry

In this paper I expand Eric Scerri’s notion of Popper’s naturalised approach to reduction in chemistry and investigate what its consequences might be. I will argue that Popper’s naturalised approach to reduction has a number of interesting consequences when applied to the reduction of chemistry to physics. One of them is that it prompts us to look at a ‘bootstrap’ approach to quantum chemistry, which is based on specific quantum theoretical theorems and practical considerations that turn quantum ‘theory’ into quantum ‘chemistry’ proper. This approach allows us to investigate some of the principles that drive theory formation in quantum chemistry. These ‘enabling theorems’ place certain limits on the explanatory latitude enjoyed by quantum chemists, and form a first step into establishing the relationship between chemistry and physics in more detail.     

What Happens Structurally when one OH- Group in Co(OH)2 is Replaced by one -CO2- Group?

Inorganic-organic hybrid materials are particularly in focus in the past few years for both chemists and physicists, because of their structural characteristics quite different from those of coordination chemistry and solid state chemistry. Such materials may be of great interest to both fundamental viewpoint and potential applications in the areas of catalysis, sorption, photochemistry, electrochemistry, magnetism, or even multi-property.     

The autonomy of chemistry: old and new problems

The autonomy of chemistry and the legitimacy of the philosophy of chemistry are usually discussed in the context of the issue of reduction of chemistry to physics, and defended making use of the failure of reductionistic claims. Until quite recent times a rather widespread viewpoint was, however, that the failure of reductionistic claims concerns actually epistemological aspect of reduction only, but the ontological reduction of chemistry to physics cannot be denied. The new problems of the autonomy of chemistry in the context of reductionism seem to be ontological and metaphysical. In the present paper it is argued that there is no need for some kind of metaphysical-ontological underpinning for rejection of the secondary positions of chemistry and philosophy of chemistry with respect to physics and philosophy of physics. The issue can be elucidated in terms of the philosophy of science accepting practical realism (also known by other names).     

Atom and aether in nineteenth-century physical science

This paper suggests that the cases made for atoms and the aether in nineteenth-century physical science were analogous, with the implication that the case for the atom was less than compelling, since there is no aether. It is argued that atoms did not play a productive role in nineteenth-century chemistry any more than the aether did in physics. Atoms and molecules did eventually find an indispensable home in chemistry but by the time that they did so they were different kinds of entities to those figuring in the speculations of those natural philosophers who were atomists. Advances in nineteenth-century chemistry were a precondition for rather than the result of the productive introduction of atoms into chemistry.

Sequential Transformations in Organic Chemistry: A Synthetic Strategy with a Future

Organic-chemical synthesis has always fascinated chemists and will not lose its importance in the future. It is a truism that all chemists—and others too—are dependent on the synthesis of those compounds with which they want to work. As a result, organic-chemical synthesis today is more than ever before the cutting edge of organic chemistry, biology, biochemistry, medicine, physics, and material science. Synthesis is also the basis of the chemical industry. For the passionate synthetic chemist, however, synthesis is much more than just a method for obtaining compounds; it is the expression of his creativity, intelligence, ability, and also his perseverance.     

Binding: A unifying notion or a pseudoconcept?

Communication between chemists and physicists working in different domains of physical chemistry may sound like a dream, but actually it must be established in order that the whole field may develop in a more efficient way. Binding is a unifying concept whose discussion may make it possible for specialists of different extractions to profit from each other's work. When different specialists speak of binding, they have some intuitive picture in mind. Does it correspond to a unique well-defined concept, or is it just a cover for ignorance? A tentative definition is proposed as a starting point for discussion, but it is also emphasized that only from an open-minded and thorough analysis of the various interpretations it should be possible to make real progress. An example showing very clearly the relationship between the various topics is that of biopolymers, whose understanding depends on the specification of the role of a variety of binding effects, from chemisorption to charge transfer to (one-dimensional) metallic binding.     

Mendeleyev revisited

Despite the periodic table having been discovered by chemists half a century before the discovery of electronic structure, modern designs are invariably based on physicists’ definition of periods. This table is a chemists’ table, reverting to the phenomenal periods that led to the table’s discovery. In doing so, the position of hydrogen is clarified.

     

P.‐O. Löwdin and the International Journal of Quantum Chemistry: A kaleidoscopic agenda for quantum chemistry

This is a article about P.‐O. Löwdin's life, his work in shaping quantum chemistry into a mature discipline at the intersection of mathematics, physics, chemistry, and biology, and his founding of the International Journal of Quantum Chemistry in 1967. Unavoidably, it is, also, a article reflecting our views about the history of quantum chemistry. We attempt to convey the complexities in the becoming of a subdiscipline, like quantum chemistry, where a variety of factors will have to be taken into consideration for a comprehensive understanding of its historical developments: the relations of chemists to the Heisenberg‐Schrödinger formulation of quantum mechanics after 1926, the institutional dynamics centered around the establishment of new courses and chairs, the research agendas and the vying for dominance within the community of quantum chemists, the methodological, and philosophical issues that have never left the quantum chemists indifferent, and, of course, the dramatic role of the computer in transforming the culture for actually practicing quantum chemistry. Furthermore, attracted by American history, culture, and ways of life, Löwdin suggested in the late 1970s that the post‐WWII character of quantum chemistry was dependent on its ability to hub a “scientific melting pot,” much like the United States of America which he viewed as a fusion of people from diverse provenances and cultures. In this article, we attempt to investigate another metaphor, that of the “kaleidoscope.” Löwdin believed that quantum chemistry's strength arose from its ability to nurture a multiplicity of heterogeneous cultural elements/subcultures and practices, interacting with each other, exchanging perspectives and modes of action, which circulated in an increasingly extended network of actors and institutional frameworks. © 2013 Wiley Periodicals, Inc.     

Carbon–sulfur bond formation via photochemical strategies: An efficient method for the synthesis of sulfur-containing compounds

The development of green and convenient methods for C–S bond formation has received significant attention because C–S bond widely occurs in many important pharmaceutical and biological compounds.Recently, visible-light photoredox catalysis has been established as an efficient and general tool for the construction of C–C and C-heteroatom bonds. In this review, we have focused on the research on recent advances in C–S bond formation via visible-light photoredox catalysis, and the growing opportuni...     

Chiral Derivatives of Achiral Molecules: Standard Classes and the Problem of a Right-Left Classification

Chemistry judging by its applications, physics according to its methods, and heavily reliant upon the tools of mathematics—that is what makes theoretical chemistry. And yet that is where its strength lies—in the variety of these sciences. It is quite natural that, in answer to specific problems, results and methods can sometimes be developed whose scope extends far beyond the original application. Rather it is a mark of quality if consequences can be found in chemistry and physics and the pathway leads via new mathematical procedures and concepts. Regrettably, any publication aiming to present such aspects will usually encounter little resonance since the linguistic confusion in science, its disciplines, and subdisciplines, lies like a veil over our understanding. The author nevertheless wishes to attempt to present, in a series of articles, results of research into chemical themes in a manner designed to appeal to the interest of chemists, without neglecting interdisciplinary aspects. All that is required to understand the argumentation is a lively interest. The first two articles are concerned with the chirality of molecules, and in particular with questions relating to the chirality phenomenon of molecules in the framework of molecular classes. In view of the algebraic nature of the mathematical methods adopted, it is not surprising that precise statements result. It appears of primary interest to establish the degree to which such statements can be considered valid for molecular models or molecules themselves.