Inorganic chemistry

 Inorganic chemistry

 Inorganic chemistry is commonly thought of as those areas within chemistry that do not deal with carbon. However, carbon is very important in many inorganic compounds, and there is a whole area of study known as organometallic chemistry that is truly a hybrid of the traditional disciplines of organic and inorganic chemistry. Some areas of inorganic chemistry that are especially important are catalysis, materials chemistry, and bioinorganic chemistry. Catalysts are chemical entities that increase the rate of a reaction without being consumed, and are typically based upon transition metals (usually) organometallic complexes of transition metals).This is an extremely important area to industry, and many of the chemists who would be identified as inorganic or organometallic chemists work in this area. Materials Chemistry is an area concerned with the design and synthesis of materials that allow the advance of technologies in nearly every area of society. Often, inorganic chemists working in this area are concerned with the synthesis and characterization of solid state compounds or inorganic polymers such as silicones. Bioinorganic chemists study the function of metal-containing compounds within living organisms. Students who concentrate in inorganic chemistry often go on to work in industry in polymer or materials science, do research or teach in inorganic chemistry, or pursue other related job opportunities.

Organic chemistry 

Organic chemistry is a sub-field of chemistry that involves studying the molecules of life. It is mainly concerned with looking at the structure and behavior of these molecules, which are composed of only a few different types of atoms: carbon, hydrogen, oxygen, nitrogen, and a few miscellaneous others. These are the atoms used to construct the molecules that all plants and animals require for their survival. Traditional organic chemists are concerned with synthesizing new molecules and with developing new reactions that might make these syntheses more efficient. The kinds of molecules organic chemists synthesize include useful things like drugs, flavorings, preservatives, fragrances, plastics (polymers), and agricultural chemicals (fertilizers and pesticides), and sometimes include unusual molecules found in nature or ones that might simply provide a challenge to make. Also, understanding something about organic chemistry is essential for learning about biochemistry and molecular biology because bio-molecules such as proteins, sugars, fats, and nucleic acids (DNA and RNA) are all organic molecules, albeit very large ones. Students who concentrate in organic chemistry typically go on to work in pharmaceutical, food or polymer companies, do research or teach in organic chemistry, pursue medical careers, or may pursue other related job opportunities.

Different types of Chemistry

 

Different types of Chemistry

Fundamentally, chemistry is the study of matter and change. The way that chemists study matter and change and the types of systems that are studied varies dramatically. Traditionally, chemistry has been broken into five main subdisciplines: Organic, Analytical, Physical, Inorganic, and Biochemistry. Over the last several years, additional concentrations have begun to emerge, including Nuclear chemistry, Polymer chemistry, Biophysical chemistry, Bioinorganic chemistry, Environmental chemistry, etceteras. All of these areas of chemistry are addressed in our classes here at UWL to some extent, and by the research interests of our faculty in the Chemistry Department. The following descriptions of the five major subdisciplines were written by several of our faculty members in their field of expertise. All of our faculty members would be happy to elaborate, and/or discuss other aspects of chemistry that are not described below! UW-La Crosse's accredited Chemistry and Biochemistry programs blend technical, hands-on research experience with practical skill development.

Organic chemistry is a sub-field of chemistry that involves studying the molecules of life. It is mainly concerned with looking at the structure and behavior of these molecules, which are composed of only a few different types of atoms: carbon, hydrogen, oxygen, nitrogen, and a few miscellaneous others. These are the atoms used to construct the molecules that all plants and animals require for their survival. Traditional organic chemists are concerned with synthesizing new molecules and with developing new reactions that might make these syntheses more efficient. The kinds of molecules organic chemists synthesize include useful things like drugs, flavorings, preservatives, fragrances, plastics (polymers), and agricultural chemicals (fertilizers and pesticides), and sometimes include unusual molecules found in nature or ones that might simply provide a challenge to make. Also, understanding something about organic chemistry is essential for learning about biochemistry and molecular biology because bio-molecules such as proteins, sugars, fats, and nucleic acids (DNA and RNA) are all organic molecules, albeit very large ones. Students who concentrate in organic chemistry typically go on to work in pharmaceutical, food or polymer companies, do research or teach in organic chemistry, pursue medical careers, or may pursue other related job opportunities.

Analytical chemistry is the science of identification and quantification of materials in a mixture. Analytical chemists may invent procedures for analysis, or they may use or modify existing ones. They also supervise, perform, and interpret the analysis. Students concentrating in analytical chemistry often go on to work in forensics laboratories, environmental or pharmaceutical companies, work in, manage and/or design quality assurance procedures, pursue research, or teach in colleges and universities.

Physical chemistry is the study of the fundamental physical principles that govern the way that atoms, molecules, and other chemical systems behave. Physical chemists study a wide array of topics such as the rates of reactions (kinetics), the way that light and matter interact (spectroscopy), how electrons are arranged in atoms and molecules (quantum mechanics), and the stabilities and reactivities of different compounds and processes (thermodynamics). In all of these cases, physical chemists try to understand what is happening on an atomic level, and why. Students who concentrate in physical chemistry may go onto pursue careers in industry, research or teaching. A lot of the current physical chemistry research in industry and academia combines the techniques and ideas from several fields. For example, some chemists apply physical chemistry techniques to investigations of the mechanisms of organic reactions (what collisions and bond rearrangements occur, how fast are they, how many steps are there, etc.) - this type of study is called physical organic chemistry. Others apply physical techniques to the study of biological systems (why do proteins fold into the shapes that they have, how is structure related to function, what makes a nerve work, etc.) - this type of study is biophysical chemistry. Still others may use physical techniques to characterize polymers or study environmental systems.

 

 Branches of chemistry

The seven major types of chemistry categorize the study of matter into specific disciplines. While often overlapping, the seven branches are organic, inorganic, physical, analytical, biochemistry, nuclear, and environmental chemistry. 

• Organic Chemistry: Focuses on the structure, properties, and reactions of carbon-containing compounds
  . It is the foundation of pharmaceuticals, plastics, and fuels.
Inorganic Chemistry: Deals with the study of compounds that do not contain carbon-hydrogen bonds, such as metals, minerals, and organometallic substances.
Physical Chemistry: Applies physics to the study of chemistry. It investigates how matter behaves on a molecular and atomic level and how chemical reactions work in terms of energy, rate, and thermodynamics.
Analytical Chemistry: Involves the qualitative and quantitative analysis of materials to identify and separate components. It is crucial for forensic science, quality control, and ensuring food safety.
Biochemistry: The study of the chemical processes and substances that occur within living organisms. It bridges biology and chemistry to explain phenomena like genetics, metabolism, and disease.
Nuclear Chemistry: Focuses on the reactions and properties of atomic nuclei. This includes the study of radioactivity, nuclear power, and medical imaging technologies.
Environmental Chemistry: Studies the chemical and biochemical processes occurring in natural places. It monitors how human activities impact ecosystems, the atmosphere, and water supplies. 

Organic radicals and the theory of chemical structure

 Organic radicals and the theory of chemical structure

Both problems were finally resolved through the further development of organic chemistry. The leading organic chemists of the day were the German Justus von Liebig and the Frenchman Jean-Baptiste-André Dumas. In 1830 Liebig invented a device that made organic analysis rapid, convenient, and accurate, and his laboratory institute at the tiny University of Giessen in Hesse became the most famous chemical school in the world. Liebig taught an enormous number of chemists, and his students assisted in his research program. He was the leading figure in the rise of the research university and in the idea of a research group. As a professor at Giessen, and later at the University of Munich, he laid much emphasis on practical applications of chemistry, especially for physiology, agriculture, and consumer products. Dumas exerted a similar influence in France, training students and pursuing research at a private laboratory in Paris.

Both Liebig and Dumas initially accepted the Berzelian scheme and sought to understand organic molecules as composed of identifiable radicals held together electrochemically. The younger French chemists Auguste Laurent and Charles Gerhardt pursued chlorine substitution reactions and cast doubt on this simple model; sometime after 1840 Liebig and Dumas both retreated into positivism. In 1852 Liebig’s English former postdoctoral assistant Edward Frankland noticed a regularity in the combining capacity of the atoms of certain metals and semimetals. At about the same time, two former students of both Liebig and Dumas, Alexander Williamson in London and Charles-Adolphe Wurtz in Paris, were independently approaching the same idea from a different direction. Using a system of atomic weights and formulas developed by Gerhardt and Laurent—a modified version of Berzelius’s system that incorporated Avogadro’s ideas more consistently—they proposed that oxygen atoms could combine with two other simple atoms, such as hydrogen, or with two organic radicals and that nitrogen atoms could combine with three. This was the beginning of the concept of atomic valence.

In 1858 the young German theorist August Kekule then expanded this concept to carbon, not only proposing that carbon atoms were tetravalent but adding the idea that they could bond to each other to form chains, comprising a molecular “skeleton” to which other atoms could cling. Kekule’s theory of chemical structure clarified the compositions of hundreds of organic compounds and served as a guide to the synthesis of thousands more. (The self-chaining of carbon atoms was independently developed by the Scottish chemist Archibald Scott Couper.) This theory experienced dramatic expansion when Kekule successfully applied it to aromatic compounds (after 1865) and after Jacobus Henricus van ’t Hoff of the Netherlands and Joseph LeBel of France independently began to investigate molecular structures in three dimensions—later called stereochemistry.

Atomic and molecular theory

 Atomic and molecular theory

Lavoisier’s set of chemical elements, and the new way of understanding chemical composition, proved to be invaluable for analytic and inorganic chemistry, but in a real sense the chemical revolution had only just begun. Around the turn of the century, the English Quaker schoolteacher John Dalton began to wonder about the invisibly small ultimate particles of which each of these elemental substances might be composed. He thought that if the atoms of each of the elements were distinct, they must be characterized by a distinct weight that is unique to each element. Although these atoms were far too small to weigh individually, he realized that he could deduce their weights relative to each other—the ratio of the weight of an atom of oxygen to one of hydrogen, for instance—by examining reacting weights of macroscopic quantities of these elements. In fact, the laws of stoichiometry (combining weights of elements) were just then being developed, and Dalton used these regularities to justify his inferences. His first discussion of these issues dates to 1803, and he presented his atomic theory in the multivolume New System of Chemical Philosophy (1808–27).

Dalton’s atomic theory was a landmark event in the history of chemistry, but it had a crucial flaw. His procedure required that one know the formulas of the simple compounds resulting from the combination of the elements. For example, analytical data of that day indicated that water resulted from the combination of seven parts by weight of oxygen with one part of hydrogen. If the resulting water molecule was HO (one atom of each element combining to form a molecule of water), then the weight ratio of the atoms of these elements must be the same, seven to one. However, if the formula were H2O, then the weight of an oxygen atom would have to be 14 times the weight of a hydrogen atom. There was simply no way to determine molecular formulas at that time, so Dalton made assumptions based on the simplicity of nature. He chose HO as his water formula and, therefore, seven as the relative atomic weight of oxygen.

In the following years, several leading chemists adopted essential elements of Dalton’s theory, but many objected to the hypothetical elements just described; some also doubted the very possibility of investigating the world of the invisibly small. In 1808 the French chemist Joseph-Louis Gay-Lussac discovered that when gases combine chemically, they do so in small integral multiples by volume. Three years later the Italian physicist Amedeo Avogadro argued that this fact suggested that equal volumes of gases contain equal numbers of constituent particles (Avogadro’s law), physical conditions being the same. This idea provided a physical method of determining certain molecular formulas. For instance, Gay-Lussac had pointed out that exactly two volumes of hydrogen combine with precisely one of oxygen to form water. If Avogadro was right, the formula for water had to be H2O. But this line of reasoning also led to the uncomfortable notion that elementary gases had polyatomic molecules (O2, H2, and so on), and therefore many chemists rejected Avogadro’s hypotheses.

By far the greatest of the early atomists was the Swede Jöns Jacob Berzelius, who accepted parts of Avogadro’s ideas and developed an elaborate version of chemical atomism by 1826. It was Berzelius who in 1813 had proposed the alphabetic system for denoting elements, atoms, and molecular formulas, and the use of formulas as an aid for studying chemical composition and reactions began to blossom about 1830. However, different chemists were still making different assumptions regarding the formulas of simple compounds such as water, and so, for decades, various inconsistent systems of atomic weights and formulas were in use in the various European countries.

Berzelius also developed a theory of chemical combination based on the electrochemical studies that the invention of the battery (1800) had spawned. He became convinced that all molecules were held together by the Coulomb force, the electrostatic attraction between oppositely charged objects. (Berzelius assumed that a molecule’s constituent atoms or groups of atoms were not neutral, and he called these charged components radicals.) This theory of electrochemical dualism worked well with inorganic compounds, but organic substances seemed anomalous. Particularly in the 1830s, when chemists learned how to replace the hydrogen of organic compounds with chlorine atoms, Berzelius’s theory appeared to be threatened—after all, hydrogen and chlorine had opposite electrochemical characteristics, yet the substitution seemed to make little difference in the properties of the compounds. In the 1840s and ’50s, extensive debates over rival systems of chemical atomism and over electrochemical dualism enlivened the journal literature.

The chemical revolution

 The chemical revolution

The new research on “airs” attracted the attention of the young French aristocrat Antoine-Laurent Lavoisier. Lavoisier commanded both the wealth and the scientific brilliance to enable him to construct elaborate apparatuses to carry out his numerous ingenious experiments. In the course of just a few years in the 1770s, Lavoisier developed a radical new system of chemistry, based on Black’s methods and Priestley’s dephlogisticated air.

Lavoisier first determined that certain metals and nonmetals absorb a gaseous substance from the air in undergoing calcination or combustion and, in the process, increase in weight. Initially, he thought that this gas must be Black’s fixed air, for he knew of no other chemical species present in ordinary air; moreover, fixed air was known to be produced in smelting, so it seemed reasonable to think that it was present in the calx that was smelted. At this point (October 1774), Priestley communicated to Lavoisier his discovery of dephlogisticated air. Further experiments led Lavoisier to continuously modify his ideas, until it finally became clear to him that it was this new gas, and not fixed air, that was the active entity in combustion, calcination, and respiration. Moreover, he determined (or so he thought, at least) that this gas was contained in all acids. He renamed it oxygen, Greek for “acid producer.”

Lavoisier’s oxygen was in some respects the inverse of phlogiston. Rather than releasing anything, the combustible or metal absorbed (more precisely, chemically combined with) oxygen in the process that Lavoisier now called oxidation. He showed that atmospheric air was a mixture of two principal components, oxygen and a physiologically inert gas (known to Priestley) that he called azote or nitrogen. He also showed that water is a chemical compound of two substances, oxygen and what Cavendish had called “inflammable air.” The latter gas was now renamed hydrogen (“water producer”). Black’s fixed air proved to be a gaseous form of oxidized carbon, or carbon dioxide. The various parts of Lavoisier’s new system were beginning to fit together beautifully.

The keys to Lavoisier’s success were twofold. First, he carefully accounted for all the substances, including gases, entering into and emerging from the chemical reactions he studied by tracking their weights with the greatest possible precision. He knew to do this partly from Black’s example, but he proceeded with a mastery that the science had never before seen. Second, he established a simple operational definition of a chemical element—namely, a substance that could not be reduced in weight as the result of any chemical reaction that it undergoes. Oxygen, carbon, iron, and sulfur were now regarded as elements, along with close to 30 other substances. Lavoisier wrote a textbook to promote the new oxygenist chemistry, Traité élémentaire de chimie (1789), which appeared in the same year the French Revolution began. He and his associates also developed a new nomenclature—essentially the one used today for inorganic compounds—along with a new journal. As an aristocrat of the ancien régime and an investor in a tax-collection agency, Lavoisier was executed in the Reign of Terror, but by that time (1794) the chemical revolution that he had started had largely succeeded in replacing phlogistonist chemistry.

Alchemy

 Alchemy

Three different sets of ideas and skills fed into the origin of alchemy. First was the empirical sophistication of jewelers, gold- and silversmiths, and other artisans who had learned how to fashion precious and semiprecious materials. Among their skills were smelting, assaying, alloying, gilding, amalgamating, distilling, sublimating, painting, and lacquering. The second component was the early Greek theory of matter, especially Aristotelian philosophy, which suggested the possibility of unlimited transformability of one kind of matter into another. The third of alchemy’s roots consisted of a complex combination of ideas derived from Asian philosophies and religions, Hellenistic mystery religions, and what became known as the Hermetic writings (a body of pseudonymous Greek writings on magic, astrology, and alchemy ascribed to the Egyptian god Thoth or his Greek counterpart Hermes Trismegistos). It is important to note, however, that Hellenistic Egypt is only one of several candidates for the homeland of alchemy; at about the same time, similar ideas were developing in Persia, China, and elsewhere.

In general, alchemists sought to manipulate the properties of matter in order to prepare more valuable substances. Their most familiar quest was to find the philosopher’s stone, a magical substance that would transmute ordinary metals such as copper, tin, iron, or lead into silver or gold. Important materials in this craft included sulfur, mercury, and electrum (a gold-silver alloy). However, many other alchemists spurned alchemical transmutation (aurifaction), devoting their efforts instead to a pharmaceutical preparation known as the “elixir of life” that would cure any disease, including the ultimate disease, death. The philosopher’s stone and the elixir of life could be considered parallel quests, for each would “cure” metallic or human bodies, respectively, yielding immortal perfection. There was a parallel religious dimension to all this as well. Finally, some alchemists spurned material manipulations entirely, devoting themselves to meditation with the goal of achieving spiritual purity and ultimate redemption.

After the rise of Islam, Arabic-speaking scholars of the 9th century translated Greek scientific and philosophical works into their own language. Thereafter, philosophers in the Islamic world pursued chemical and alchemical ideas with enthusiasm and success. The sizable number of modern chemical words derived from Arabic—alcohol, alkali, alchemy, zircon, elixir, natron, and others—suggests the importance of this period for the history of chemistry. One of the leading ideas of medieval Arabic alchemy was the theory that all metals were formed of sulfur and mercury in various proportions and that altering those proportions could transform the metal under study—even to produce silver or gold from lead or iron. Not every alchemist, however, believed in the possibility of such transmutations.

Later, scholars in Christian western Europe learned of ancient Greek and early medieval Arabic philosophy by translating these books into Latin. Thus, the alchemical tradition, along with the rest of the Greco-Arabic philosophical and scientific corpus, passed to the West in the course of the 12th century. Well-known Scholastic philosophers of the 13th century, such as Roger Bacon in England and Albertus Magnus in Germany and France, wrote on alchemy. Alongside this learned literature, the empirical chemical arts continued to flourish and comprised a largely separate realm of expertise among artisans, engineers, and mechanics.

An important Western alchemist of the late 13th century was the pseudonymous Latin writer who called himself Geber in homage to the 8th-century Arab alchemist Jābir ibn Ḥayyān. Geber was the first to record methods for the preparation and use of sulfuric acid, nitric acid, and hydrochloric acid; the earliest clear evidence for widespread familiarity with distilled alcohol also does not much predate his day. These substances could only have been produced by novel stills that were more robust and efficient than their predecessors, and the appearance of these remarkable new materials produced dramatic changes in the repertoire of chemists.

The Renaissance saw even stronger interest in the science. The German-Swiss physician Paracelsus practiced alchemy, Kabbala, astrology, and magic, and in the first half of the 16th century he championed the role of mineral rather than herbal remedies. His emphasis on chemicals in pharmacy and medicine was influential on later figures, and lively controversies over the Paracelsian approach raged around the turn of the 17th century. Gradually the Hermetic influence declined in Europe, however, as certain celebrated feats of putative aurifaction were revealed as frauds.