Industrial chemistry

The manufacture, sale, and distribution of chemical products is one of the cornerstones of a developed country. Chemists play an important role in the manufacture, inspection, and safe handling of chemical products, as well as in product development and general management. The manufacture of basic chemicals such as oxygen, chlorine, ammonia, and sulfuric acid provides the raw materials for industries producing textiles, agricultural products, metals, paints, and pulp and paper. Specialty chemicals are produced in smaller amounts for industries involved with such products as pharmaceuticals, foodstuffs, packaging, detergents, flavours, and fragrances. To a large extent, the chemical industry takes the products and reactions common to “bench-top” chemical processes and scales them up to industrial quantities.

The monitoring and control of bulk chemical processes, especially with regard to heat transfer, pose problems usually tackled by chemists and chemical engineers. The disposal of by-products also is a major problem for bulk chemical producers. These and other challenges of industrial chemistry set it apart from the more purely intellectual disciplines of chemistry discussed above. Yet, within the chemical industry, there is a considerable amount of fundamental research undertaken within traditional specialties. Most large chemical companies have research-and-development capability. Pharmaceutical firms, for example, operate large research laboratories in which chemists test molecules for pharmacological activity. The new products and processes that are discovered in such laboratories are often patented and become a source of profit for the company funding the research. A great deal of the research conducted in the chemical industry can be termed applied research because its goals are closely tied to the products and processes of the company concerned. New technologies often require much chemical expertise. The fabrication of, say, electronic microcircuits involves close to 100 separate chemical steps from start to finish. Thus, the chemical industry evolves with the technological advances of the modern world and at the same time often contributes to the rate of progress.

 Polymer chemistry

The simple substance ethylene is a gas composed of molecules with the formula CH2CH2. Under certain conditions, many ethylene molecules will join together to form a long chain called polyethylene, with the formula (CH2CH2)n, where n is a variable but large number. Polyethylene is a tough, durable solid material quite different from ethylene. It is an example of a polymer, which is a large molecule made up of many smaller molecules (monomers), usually joined together in a linear fashion. Many naturally occurring substances, including cellulose, starch, cotton, wool, rubber, leather, proteins, and DNA, are polymers. Polyethylene, nylon, and acrylics are examples of synthetic polymers. The study of such materials lies within the domain of polymer chemistry, a specialty that has flourished in the 20th century. The investigation of natural polymers overlaps considerably with biochemistry, but the synthesis of new polymers, the investigation of polymerization processes, and the characterization of the structure and properties of polymeric materials all pose unique problems for polymer chemists.

Polymer chemists have designed and synthesized polymers that vary in hardness, flexibility, softening temperature, solubility in water, and biodegradability. They have produced polymeric materials that are as strong as steel yet lighter and more resistant to corrosion. Oil, natural gas, and water pipelines are now routinely constructed of plastic pipe. In recent years, automakers have increased their use of plastic components to build lighter vehicles that consume less fuel. Other industries such as those involved in the manufacture of textiles, rubber, paper, and packaging materials are built upon polymer chemistry.

Besides producing new kinds of polymeric materials, researchers are concerned with developing special catalysts that are required by the large-scale industrial synthesis of commercial polymers. Without such catalysts, the polymerization process would be very slow in certain cases.

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.

History of Paint

 

History of Paint

The abundance and widespread use of paint in our daily lives makes it easy to take paint for granted. A look at the chemistry of paint leads to a better appreciation of its complexities.

Paint is a liquid composition that dries to an opaque film. It is composed of four basic types of ingredients: pigments, which are powders that give opacity and color; binders, which act like glue to hold the pigments together and cause the film to adhere to the surface being painted; liquids, which make the paint thin enough to spread on a surface, and additives, which perform special functions such as thickening, reducing mildew, and more.

Paints are generally classified as either solvent-borne or waterborne. Solvent-borne wall paints, such as oil paints, use a petroleum derivative (for example, mineral spirits) as the solvent. Waterborne paints use water.

Waterborne wall coatings prevailed from prehistoric cave paintings up to medieval wall paintings. Natural proteins were used as binders for the pigments. Tempera used egg whites as a binder; distemper, a similar waterborne paint, used animal glues from hides and hoofs. Whitewash used milk casein to bind lime (calcium hydroxide) onto Tom Sawyer's fictional fence. But all these exhibited poor washability and durability.

Linseed-oil-bound pigments — used by the ancient Egyptians, early Romans and Renaissance artists such as da Vinci and Michelangelo — were more durable, but were scarce until the linen industry expanded to provide ample flax seed, from which linseed oil was pressed. Hardening of the soft linseed oil films by rosin and adding volatile turpentine from the naval stores industry enhanced varnishes for Stradivarius violins, fine furniture and wooden floors. Turpentine was the only historic volatile organic solvent to control paint viscosities until the coke and petroleum industries distilled various naphthas.

These separate crafts came together only in the 1930s, when brilliant exterior waterborne paints enhanced and survived the 1933 Century of Progress Exposition in Chicago and the 1939-40 World's Fair in New York City.

World War II Brings Changes to Paint Industry

 

World War II Brings Changes to Paint Industry

During World War II, the paint industry geared up for defense production. Thousands of military items required paints, including camouflage paint for tanks; aircraft, ship, and truck finishes; and coatings for guns and bombs. Every soldier was equipped with many painted items, some of which had their own special finishes. In addition, construction equipment, water supplies, and electrical lighting systems necessary to a military campaign also required paint.

Sherwin-Williams, a leading paint manufacturer based in Cleveland, Ohio, worked to accommodate this defense conversion. Plant engineers converted old equipment to new manufacturing uses. Chemists experimented with old, almost forgotten oils and resins and treated them with modern processing equipment. Purchasing agents combed the country for raw materials so that shortages would not halt production.

Shortages affected every corner of life during the war, from women who gave up stockings because silk was unavailable, to paint manufacturers who were required to ration linseed oil, a common paint binder. These constraints led Sherwin-Williams to accelerate their research into new coatings concepts. Their chemists took casein, a milk protein used by the ancient Egyptians for making paint, and emulsified (or suspended) varnish in it. They then added a number of other ingredients, with water as the largest component, to create a water-based paint.

The result was Kem-Tone^© paint, a fast-drying emulsion that met with instant public acceptance and would ultimately become one of the best-selling paints in the United States. Kem-Tone^© paint became the first widely accepted waterborne interior wall paint with sufficient binding power to allow washability.

Developed by a team of Sherwin-Williams chemists, Kem-Tone^© paint did not depend on organic solvents (based on carbon, such as petroleum derivatives), and it reduced the required amounts of traditional binders, which were in short supply because of the war. Technologically, the chemists at Sherwin-Williams showed that it was chemically and commercially possible for a paint emulsified in water to produce a durable coating.

Kem-Tone^© was registered as a trademark on Sept. 23, 1941. In the next three years, more than 10 million gallons would be sold.

The widespread acceptance of Kem-Tone^© paint was accelerated by the simultaneous introduction of the hand-roller (called Roller-Koater™), which made application by do-it-yourselfers very easy. Here, too, wartime shortages played a significant role. Richard Adams, an engineer for Sherwin-Williams, invented and patented the roller as an alternative to brushes, which were in short supply because the war between China and Japan restricted the availability of hog bristles.

Kem-Tone^© paint and the Roller-Koater™ applicator ushered in a new era in the do-it-yourself paint market, which comprises about 50 percent of the architectural coatings (paints applied to residences) sold today. The innovative chemistry of Kem-Tone^© paint also opened the door to continued developments in waterborne paints, which account for approximately 80 percent of all the architectural coatings sold today.

Chemistry of Flavor

 

Chemistry of Flavor

Flavor is caused by receptors in the mouth and nose detecting chemicals found within food. These receptors respond by producing signals that are interpreted by the brain as sensations of taste and aroma. Certain taste and aroma combinations are characteristic of particular foods.

For example, a green apple tastes the way it does because the unique combination of chemicals found naturally within it are perceived by our mouths, noses and brains as the distinct blend of sweet and sour tastes and volatile aromas characteristic to the fruit. Identifying this chemical profile allows food producers to retain flavor in preserved green apples and, through synthesis of these flavor compounds, makes possible the production of candy, soda and other products using artificial green apple flavor.

The chemicals that produce flavors are notoriously difficult to study because a single natural flavor may contain hundreds or even thousands of component substances, and some of these substances are present in minute quantities. For example, one of the nine key aroma compounds found in pineapple is so potent that human subjects can detect it at only 6 parts per trillion—the equivalent of a few grains of sugar in an Olympic-size swimming pool. Understanding the components of flavor has become more important than ever with the modernization of food systems and the increased reliance on processed foods.

What is flavor?

 

What is flavor?

Taste plus smell equals flavor. We can detect five tastes (sweet, salty, bitter, sour and umami), and we can smell as many as 40 billion molecules. When they mix together in food, that can translate to more than a trillion possible flavors.

What does flavor have to do with chemistry?

Everything! We experience flavor in our brains, but it depends on taste and smell, which are chemical senses. That means we’re using our tongue and nose to sense molecules. Everything you taste—all the flavors you’ve ever experienced—are molecules.   

Can you tell how a molecule is going to taste from its structure?

We don’t have a perfect roadmap for flavor perception based on chemistry the way we do for color and sound, which are based on physics. But we do have a pretty good idea about a lot of things. For example, if you have a carbohydrate that’s not very big, there’s a good chance it’s going to be sweet. If a molecule is an acid, it’s almost definitely sour. 

Why do some plants produce seeds, roots, and bark that taste so good to humans?

We still don’t have a great idea about how to predict how a molecule smells just from its structure. We know from genetics that humans have around 400 types of smell receptors, but we’re still figuring out how they all work. We can make an educated guess about what a molecule is going to smell like, but it’s still a mystery how the brain translates signals from the smell receptors into the psychological experience of a smell or a flavor. 

Some people are using AI to analyze very large data sets to understand it. Others are taking a biology route by growing receptors in Petri dishes and seeing what kind of molecules they bind to. Some people are doing X-ray crystallography and structural studies to better understand the molecules themselves. Pretty much every area of chemistry has something useful to tell us about how flavor and smell work.

Synthetic Food

Synthetic Food

 In January 1976, the U.S. Food and Drug Administration (FDA) banned a popular and well-studied chemical used in food: Red 2. Food colorants have long been contentious, misunderstood and a target for chemistry researchers hunting for a breakthrough. 

Chemists first synthesized the molecule Red 2 in the late 1800s. They isolated the color from coal tar initially, then petroleum. Red 2 became the most popular dye in the food industry. Then, around 1970, the results of lab experiments seemed to challenge its safety. Public concern grew, and politicians urged the FDA to continue testing Red 2. Supporters of a ban claimed that the food colorant caused birth defects and cancer. Yet while further tests from FDA chemists proved inconclusive, the agency ordered food companies to stop using Red 2. As a result, the candymaker Mars paused making red M&Ms, although, ironically, red M&Ms did not contain the banned red dye—public anxiety had simply swelled so much that Mars wouldn’t risk losing business to any confusion.

As the U.S. government seeks additional bans on food colorants, both support and skepticism have again flooded in. In the final weeks of the Biden administration, the FDA moved to ban Red 3 from food and drugs. West Virginia has adopted the strictest ban on seven synthetic food dyes, and California has banned six.

Synthetic food dyes have just been better. Their colors tend to be more vibrant, and their chemical makeup tends to be more resilient against the (literal) pressures of food manufacturing: high temperatures, extrusion and pH changes. Natural dyes are more fragile in part because they are often extracted alongside sugar and other flavoring molecules that decompose under stress. This extra baggage also comes with an unwanted taste (unless a paprika-flavored sports drink sounds good to you). Natural food colors are often more expensive as well, and people tend to prefer buying brightly colored foods. 

However, public perception is that natural alternatives are considered safer. If the debate is a matter of health and death, then siding against synthetic food colors should be easy. But the truth is more complicated. 

“Natural” additives, such as annatto and saffron, can cause mild allergic reactions. Only a few synthetic colors have conclusive evidence of being toxic. Often, the dose required to cause harm is absurdly high. And while critics refer to synthetic food colors as “petroleum derived,” this label is misleading. “A 60 pound kid can eat 472 Skittles every day before hitting the [safe limit] for Red 40,” wrote immunologist Andrea Love in her newsletter ImmunoLogic. “A chemical behaves based on its identity, not its origin.”

The colorful dispute draws all sorts of criticism and support. Some candymakers want to keep using synthetic colorants; some consumer advocate groups fear the bans won’t be enforced. And research companies working on natural food colorants believe this is their moment.

Chemists can engineer natural dyes to with-stand heat and pH changes by enveloping them in polymers. They can also produce purer natural colors by tasking microscopic yeast to grow large batches in labs. This “fermentation-derived” color can also avoid unwanted veggie flavors. With-standing high pressures (like the force of pushing cereal through a shaping machine) is harder. But one company has invented a heat-stable blue gelatin powder based on extract from a Peruvian fruit called jagua. Jagua earned FDA approval in 2023.

In May 2025, the FDA approved three more natural colors as food additives: white calcium phosphate; a blue color from Galdieria algae; and butterfly pea flower extract, which can appear blue, purple, green or red, depending on acidity.

The red M&M remained discontinued until 1987. When it returned, Mars had switched to coloring it with Red 40—one of the synthetic dyes the FDA now wants to phase out. Which dye might be used next in the candy? Perhaps carmine, a food pigment made from crushed cochineal insects, which is already in use in European M&Ms.

 

Chemistry and society

For the first two-thirds of the 20th century, chemistry was seen by many as the science of the future. The potential of chemical products for enriching society appeared to be unlimited. Increasingly, however, and especially in the public mind, the negative aspects of chemistry have come to the fore. Disposal of chemical by-products at waste-disposal sites of limited capacity has resulted in environmental and health problems of enormous concern. The legitimate use of drugs for the medically supervised treatment of diseases has been tainted by the growing misuse of mood-altering drugs. The very word chemicals has come to be used all too frequently in a pejorative sense. There is, as a result, a danger that the pursuit and application of chemical knowledge may be seen as bearing risks that outweigh the benefits.

It is easy to underestimate the central role of chemistry in modern society, but chemical products are essential if the world’s population is to be clothed, housed, and fed. The world’s reserves of fossil fuels (e.g., oil, natural gas, and coal) will eventually be exhausted, some as soon as the 21st century, and new chemical processes and materials will provide a crucial alternative energy source. The conversion of solar energy to more concentrated, useful forms, for example, will rely heavily on discoveries in chemistry. Long-term, environmentally acceptable solutions to pollution problems are not attainable without chemical knowledge. There is much truth in the aphorism that “chemical problems require chemical solutions.” Chemical inquiry will lead to a better understanding of the behaviour of both natural and synthetic materials and to the discovery of new substances that will help future generations better supply their needs and deal with their problems.

Progress in chemistry can no longer be measured only in terms of economics and utility. The discovery and manufacture of new chemical goods must continue to be economically feasible but must be environmentally acceptable as well. The impact of new substances on the environment can now be assessed before large-scale production begins, and environmental compatibility has become a valued property of new materials. For example, compounds consisting of carbon fully bonded to chlorine and fluorine, called chlorofluorocarbons (or Freons), were believed to be ideal for their intended use when they were first discovered. They are nontoxic, nonflammable gases and volatile liquids that are very stable. These properties led to their widespread use as solvents, refrigerants, and propellants in aerosol containers. Time has shown, however, that these compounds decompose in the upper regions of the atmosphere and that the decomposition products act to destroy stratospheric ozone. Limits have now been placed on the use of chlorofluorocarbons, but it is impossible to recover the amounts already dispersed into the atmosphere.

The chlorofluorocarbon problem illustrates how difficult it is to anticipate the overall impact that new materials can have on the environment. Chemists are working to develop methods of assessment, and prevailing chemical theory provides the working tools. Once a substance has been identified as hazardous to the existing ecological balance, it is the responsibility of chemists to locate that substance and neutralize it, limiting the damage it can do or removing it from the environment entirely. The last years of the 20th century will see many new, exciting discoveries in the processes and products of chemistry. Inevitably, the harmful effects of some substances will outweigh their benefits, and their use will have to be limited. Yet, the positive impact of chemistry on society as a whole seems beyond doubt.

Energy and the first law of thermodynamics

 

Energy and the first law of thermodynamics

The concept of energy is a fundamental and familiar one in all the sciences. In simple terms, the energy of a body represents its ability to do work, and work itself is a force acting over a distance.

Chemical systems can have both kinetic energy (energy of motion) and potential energy (stored energy). The kinetic energy possessed by any collection of molecules in a solid, liquid, or gas is known as its thermal energy. Since liquids expand when they have more thermal energy, a liquid column of mercury, for example, will rise higher in an evacuated tube as it becomes warmer. In this way a thermometer can be used to measure the thermal energy, or temperature, of a system. The temperature at which all molecular motion comes to a halt is known as absolute zero.

Energy also may be stored in atoms or molecules as potential energy. When protons and neutrons combine to form the nucleus of a certain element, the reduction in potential energy is matched by the production of a huge quantity of kinetic energy. Consider, for instance, the formation of the deuterium nucleus from one proton and one neutron. The fundamental mass unit of the chemist is the mole, which represents the mass, in grams, of 6.02 × 1023 individual particles, whether they be atoms or molecules. One mole of protons has a mass of 1.007825 grams and one mole of neutrons has a mass of 1.008665 grams. By simple addition the mass of one mole of deuterium atoms (ignoring the negligible mass of one mole of electrons) should be 2.016490 grams. The measured mass is 0.00239 gram less than this. The missing mass is known as the binding energy of the nucleus and represents the mass equivalent of the energy released by nucleus formation. By using Einstein’s formula for the conversion of mass to energy (E = mc2), one can calculate the energy equivalent of 0.00239 gram as 2.15 × 108 kilojoules. This is approximately 240,000 times greater than the energy released by the combustion of one mole of methane. Such studies of the energetics of atom formation and interconversion are part of a specialty known as nuclear chemistry.

The energy released by the combustion of methane is about 900 kilojoules per mole. Although much less than the energy released by nuclear reactions, the energy given off by a chemical process such as combustion is great enough to be perceived as heat and light. Energy is released in so-called exothermic reactions because the chemical bonds in the product molecules, carbon dioxide and water, are stronger and stabler than those in the reactant molecules, methane and oxygen. The chemical potential energy of the system has decreased, and most of the released energy appears as heat, while some appears as radiant energy, or light. The heat produced by such a combustion reaction will raise the temperature of the surrounding air and, at constant pressure, increase its volume. This expansion of air results in work being done. In the cylinder of an internal-combustion engine, for example, the combustion of gasoline results in hot gases that expand against a moving piston. The motion of the piston turns a crankshaft, which then propels the vehicle. In this case, chemical potential energy has been converted to thermal energy, some of which produces useful work. This process illustrates a statement of the conservation of energy known as the first law of thermodynamics. This law states that, for an exothermic reaction, the energy released by the chemical system is equal to the heat gained by the surroundings plus the work performed. By measuring the heat and work quantities that accompany chemical reactions, it is possible to ascertain the energy differences between the reactants and the products of various reactions. In this manner, the potential energy stored in a variety of molecules can be determined, and the energy changes that accompany chemical reactions can be calculated.

Studies of molecular structure

 

Studies of molecular structure

The chemical properties of a substance are a function of its structure, and the techniques of X-ray crystallography now enable chemists to determine the precise atomic arrangement of complex molecules. A molecule is an ordered assembly of atoms. Each atom in a molecule is connected to one or more neighbouring atoms by a chemical bond. The length of bonds and the angles between adjacent bonds are all important in describing molecular structure, and a comprehensive theory of chemical bonding is one of the major achievements of modern chemistry. Fundamental to bonding theory is the atomic–molecular concept.

Atoms and elements

As far as general chemistry is concerned, atoms are composed of the three fundamental particles: the proton, the neutron, and the electron. Although the proton and the neutron are themselves composed of smaller units, their substructure has little impact on chemical transformation. As was explained in an earlier section, the proton carries a charge of +1, and the number of protons in an atomic nucleus distinguishes one type of chemical atom from another. The simplest atom of all, hydrogen, has a nucleus composed of a single proton. The neutron has very nearly the same mass as the proton, but it has no charge. Neutrons are contained with protons in the nucleus of all atoms other than hydrogen. The atom with one proton and one neutron in its nucleus is called deuterium. Because it has only one proton, deuterium exhibits the same chemical properties as hydrogen but has a different mass. Hydrogen and deuterium are examples of related atoms called isotopes. The third atomic particle, the electron, has a charge of -1, but its mass is 1,836 times smaller than that of a proton. The electron occupies a region of space outside the nucleus termed an orbital. Some orbitals are spherical with the nucleus at the centre. Because electrons have so little mass and move about at speeds close to half that of light, they exhibit the same wave–particle duality as photons of light. This means that some of the properties of an electron are best described by considering the electron to be a particle, while other properties are consistent with the behaviour of a standing wave. The energy of a standing wave, such as a vibrating string, is distributed over the region of space defined by the two fixed ends and the up-and-down extremes of vibration. Such a wave does not exist in a fixed region of space as does a particle. Early models of atomic structure envisioned the electron as a particle orbiting the nucleus, but electron orbitals are now interpreted as the regions of space occupied by standing waves called wave functions. These wave functions represent the regions of space around the nucleus in which the probability of finding an electron is high. They play an important role in bonding theory, as will be discussed later.

Each proton in an atomic nucleus requires an electron for electrical neutrality. Thus, as the number of protons in a nucleus increases, so too does the number of electrons. The electrons, alone or in pairs, occupy orbitals increasingly distant from the nucleus. Electrons farther from the nucleus are attracted less strongly by the protons in the nucleus, and they can be removed more easily from the atom. The energy required to move an electron from one orbital to another, or from one orbital to free space, gives a measure of the energy level of the orbitals. These energies have been found to have distinct, fixed values; they are said to be quantized. The energy differences between orbitals give rise to the characteristic patterns of light absorption or emission that are unique to each chemical atom.

A new chemical atom—that is, an element—results each time another proton is added to an atomic nucleus. Consecutive addition of protons generates the whole range of elements known to exist in the universe. Compounds are formed when two or more different elements combine through atomic bonding. Such bond formation is a consequence of electron pairing and constitutes the foundation of all structural chemistry.