The philosophy of chemistry considers the methodology and underlying assumptions of the science of chemistry. It is explored by philosophers, chemists, and philosopher-chemist teams. For much of its history, philosophy of science has been dominated by the philosophy of physics, but the philosophical questions that arise from chemistry have received increasing attention since the latter part of the 20th century.
Methodology is the systematic, theoretical analysis of the methods applied to a field of study. It comprises the theoretical analysis of the body of methods and principles associated with a branch of knowledge. Typically, it encompasses concepts such as paradigm, theoretical model, phases and quantitative or qualitative techniques.
Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.
Major philosophical questions arise as soon as one attempts to define chemistry and what it studies. Atoms and molecules are often assumed to be the fundamental units of chemical theory,but traditional descriptions of molecular structure and chemical bonding fail to account for the properties of many substances, including metals and metal complexes and aromaticity.
An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers.
A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions.
A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force of attraction between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force and hydrogen bonding.
Additionally, chemists frequently use non-existent chemical entities like resonance structures [ citation needed ]to explain the structure and reactions of different substances; these explanatory tools use the language and graphical representations of molecules to describe the behavior of chemicals and chemical reactions that in reality do not behave as straightforward molecules.
In chemistry, resonance is a way of describing bonding in certain molecules or ions by the combination of several contributing structures into a resonance hybrid in valence bond theory. It has particular value for describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by one single Lewis structure.
Some chemists and philosophers of chemistry prefer to think of substances, rather than microstructures, as the fundamental units of study in chemistry. There is not always a one-to-one correspondence between the two methods of classifying substances.For example, many rocks exist as mineral complexes composed of multiple ions that do not occur in fixed proportions or spatial relationships to one another.
A related philosophical problem is whether chemistry is the study of substances or reactions.Atoms, even in a solid, are in perpetual motion and under the right conditions many chemicals react spontaneously to form new products. A variety of environmental variables contribute to a substance's properties, including temperature and pressure, proximity to other molecules and the presence of a magnetic field. As Schummer puts it, "Substance philosophers define a chemical reaction by the change of certain substances, whereas process philosophers define a substance by its characteristic chemical reactions."
Philosophers of chemistry discuss issues of symmetry and chirality in nature. Organic (i.e., carbon-based) molecules are those most often chiral. Amino acids, nucleic acids and sugars, all of which are found exclusively as a single enantiomer in organisms, are the basic chemical units of life. Chemists, biochemists, and biologists alike debate the origins of this homochirality. Philosophers debate facts regarding the origin of this phenomenon, namely whether it emerged contingently, amid a lifeless racemic environment or if other processes were at play. Some speculate that answers can only be found in comparison to extraterrestrial life, if it is ever found. Other philosophers question whether there exists a bias toward assumptions of nature as symmetrical, thereby causing resistance to any evidence to the contrary.[ citation needed ]
Symmetry in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definition, that an object is invariant to any of various transformations; including reflection, rotation or scaling. Although these two meanings of "symmetry" can sometimes be told apart, they are related, so in this article they are discussed together.
Chirality is a geometric property of some molecules and ions. A chiral molecule/ion is non-superposable on its mirror image. The presence of an asymmetric carbon center is one of several structural features that induce chirality in organic and inorganic molecules. The term chirality is derived from the Ancient Greek word for hand, χεῖρ (kheir).
Organic chemistry is a subdiscipline of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding. Study of structure determines their chemical composition and formula. Study of properties includes physical and chemical properties, and evaluation of chemical reactivity to understand their behavior. The study of organic reactions includes the chemical synthesis of natural products, drugs, and polymers, and study of individual organic molecules in the laboratory and via theoretical study.
One of the most topical issues is determining to what extent physics, specifically, quantum mechanics, explains chemical phenomena. Can chemistry, in fact, be reduced to physics as has been assumed by many, or are there inexplicable gaps? Some authors, for example, Roald Hoffmann, [ citation needed ]have recently suggested that a number of difficulties exist in the reductionist program with concepts like aromaticity, pH, reactivity, nucleophilicity, for example. The noted philosopher of science, Karl Popper, among others, predicted as much.
Several philosophers and scientists have focused on the philosophy of chemistry in recent years, notably, the Dutch philosopher Jaap van Brakel, who wrote The Philosophy of Chemistry in 2000, and the Maltese philosopher-chemist Eric Scerri, editor of the journal "Foundations of Chemistry" and author of Normative and Descriptive Philosophy of Science and the Role of Chemistry in Philosophy of Chemistry, 2004, among other articles. Scerri is especially interested in the philosophical foundations of the periodic table, and how physics and chemistry intersect in relation to it, which he contends is not merely a matter for science, but for philosophy.
Although in other fields of science students of the method are generally not practitioners in the field, in chemistry (particularly in synthetic organic chemistry) intellectual method and philosophical foundations are often explored by investigators with active research programmes. Elias James Corey developed the concept of "retrosynthesis" published a seminal work "The logic of chemical synthesis" which deconstructs these thought processes and speculates on computer-assisted synthesis. Other chemists such as K. C. Nicolaou (co-author of Classics in Total Synthesis) have followed in his lead.
Adolph Wilhelm Hermann Kolbe was a seminal contributor in the birth of modern organic chemistry. He was a Professor at Marburg and Leipzig. Kolbe coined the term synthesis and contributed to the philosophical demise of vitalism through synthesis of the organic substance acetic acid from carbon disulfide, and also contributed to the development of structural theory. This was done via modifications to the idea of "radicals" and accurate prediction of the existence of secondary and tertiary alcohols, and to the emerging array of organic reactions through his Kolbe electrolysis of carboxylate salts, the Kolbe-Schmitt reaction in the preparation of aspirin and the Kolbe nitrile synthesis. After studies with Wöhler and Bunsen, Kolbe was involved with the early internationalization of chemistry through overseas work in London, and rose through the ranks of his field to edit the Journal für Praktische Chemie. As such, he was elected to the Royal Swedish Academy of Sciences won the Royal Society of London's Davy Medal in the year of his death. Despite these accomplishments and his training a storied next generation of chemists, Kolbe is remembered for editing the Journal for more than a decade, where his rejection of Kekulé's structure of benzene, van't Hoff's theory on the origin of chirality and von Baeyer's reforms of nomenclature were personally critical and linguistically violent. Kolbe died of a heart attack in Leipzig at age 68, six years after the death of his wife, Charlotte. He was survived by four children.
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei, and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur.
The following outline is provided as an overview of and topical guide to chemistry:
In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds. Chemical affinity can also refer to the tendency of an atom or compound to combine by chemical reaction with atoms or compounds of unlike composition.
Physical chemistry is the study of macroscopic, atomic, subatomic, and particulate phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mechanics, analytical dynamics and chemical equilibrium.
Physical science is a branch of natural science that studies non-living systems, in contrast to life science. It in turn has many branches, each referred to as a "physical science", together called the "physical sciences".
The following outline is provided as an overview of and topical guide to organic chemistry:
Robert Burns Woodward was an American organic chemist. He is considered by many to be the preeminent organic chemist of the twentieth century, having made many key contributions to the subject, especially in the synthesis of complex natural products and the determination of their molecular structure. He also worked closely with Roald Hoffmann on theoretical studies of chemical reactions. He was awarded the Nobel Prize in Chemistry in 1965.
The history of chemistry represents a time span from ancient history to the present. By 1000 BC, civilizations used technologies that would eventually form the basis of the various branches of chemistry. Examples include extracting metals from ores, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap, making glass, and making alloys like bronze.
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: total synthesis, semisynthesis, and methodology.
Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as: a chemical reaction in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric products in unequal amounts.
A cyclic compound is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where all the atoms are carbon, none of the atoms are carbon, or where both carbon and non-carbon atoms are present. Depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, carbocyclic and heterocyclic compounds may be aromatic or non-aromatic, in the latter case, they may vary from being fully saturated to having varying numbers of multiple bonds between the ring atoms. Because of the tremendous diversity allowed, in combination, by the valences of common atoms and their ability to form rings, the number of possible cyclic structures, even of small size numbers in the many billions.
The timeline of chemistry lists important works, discoveries, ideas, inventions, and experiments that significantly changed humanity's understanding of the modern science known as chemistry, defined as the scientific study of the composition of matter and of its interactions. The history of chemistry in its modern form arguably began with the Irish scientist Robert Boyle, though its roots can be traced back to the earliest recorded history.
A chemical substance is a form of matter having constant chemical composition and characteristic properties. A chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be simple substances, chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.
Physical organic chemistry, a term coined by Louis Hammett in 1940, refers to a discipline of organic chemistry that focuses on the relationship between chemical structures and reactivity, in particular, applying experimental tools of physical chemistry to the study of organic molecules. Specific focal points of study include the rates of organic reactions, the relative chemical stabilities of the starting materials, reactive intermediates, transition states, and products of chemical reactions, and non-covalent aspects of solvation and molecular interactions that influence chemical reactivity. Such studies provide theoretical and practical frameworks to understand how changes in structure in solution or solid-state contexts impact reaction mechanism and rate for each organic reaction of interest.
Eric R. Scerri is a chemist, writer and philosopher of science, of Maltese origin. He is a lecturer at the University of California, Los Angeles; and the founder and editor-in-chief of Foundations of Chemistry, an international peer reviewed journal covering the history and philosophy of chemistry, and chemical education.