Wallace Carothers invented the first synthetic rubber called neoprene in 1931. Neoprene was the first polyester. Carothers went on to invent nylon, a true silk replacement, in 1935. Paul Flory was awarded the Nobel Prize in Chemistry in 1974 for his work on polymer random coil configurations in solution in the 1950s. Stephanie Kwolek developed an aramid, or aromatic nylon named Kevlar, patented in 1966.
There are now a large number of commercial polymers. They include composite materials such as carbon fiber-epoxy, polystyrene-polybutadiene (HIPS), acrylonitrile-butadiene-styrene (ABS). Chemists design commercial polymers to combine the best properties of their various components. For example, special polymers used in automobile engines are designed to work at high temperatures.
It took a long time before universities introduced teaching and research programs in polymer chemistry.
An "Institut fur Makromolekulare Chemie was founded in 1940 in Freiburg, Germany under the direction of Hermann Staudinger. In America a "Polymer Research Institute" (PRI) was established in 1941 by Herman Mark at the Polytechnic Institute of Brooklyn (now Polytechnic Institute of NYU). Several hundred graduates of PRI played an important role in the US polymer industry and academia. Other PRI's were founded in 1961 by Richard S. Stein at the University of Massachusetts, Amherst, in 1967 by Eric Baer at Case Western Reserve University and in 1988 at the University of Akron.
Chemical synthesis
In chemistry, chemical synthesis means using chemical reactions to get a product, or several products. This happens by physical and chemical manipulations. Often, several different chemical reactions are used; one after another. In modern laboratory usage, a chemical synthesis is reproducible (if the experiment is done a second time, it will have the same results as the first time), reliable (not broken by small changes in conditions), and established to work in multiple laboratories.
Chemists start to design a chemical synthesis by selecting compounds to combine. These starting chemicals are known as reagents or reactants. Chemists do various things to these reagents to synthesize the product, or an intermediate product. This requires mixing the compounds in a reaction vessel. The vessel can be a chemical reactor or a simple flask. Many reactions require some form of work-up procedure before the final product is isolated.
The amount of product in a chemical synthesis is the reaction yield. Typically, chemical yields are expressed as a weight in grams or as a percentage of the total theoretical quantity of product that could be produced. A side reaction is an unwanted chemical reaction taking place that reduces the yield of the wanted product.
The chemist Adolph Wilhelm Hermann Kolbe was the first to use the word "synthesis" in its present-day meaning.
In most cases, a single reaction will not convert a reactant (starting chemical) into the desired reaction product. Chemists have many strategies to find the best sequence of reactions to make the desired product. In cascade reactions multiple chemical changes take place within a single reactant. In multi-component reactions up to 11 different reactants form a single reaction product. In a telescopic synthesis, one reactant goes through multiple transformations without isolating intermediates after each step.
Organic synthesis is a special type of chemical synthesis. Only organic compounds are created in organic synthesis. The total synthesis of a complex product may take many steps to reach the goal product. These steps can take too much time. Chemists want to have skill in organic synthesis and being able to find a synthesis path with the least number of steps. The synthesis of very valuable or difficult compounds has earned chemists, such as Robert Burns Woodward, the Nobel Prize in Chemistry.
If a chemical synthesis starts from basic laboratory compounds and yields something new, it is a "purely synthetic process". If it starts from a product isolated from plants or animals and then proceeds to a new compounds, the synthesis is called a "semisynthetic process".
Most times, chemical synthesis means the overall, many step procedure for making a desired product. Sometimes, chemists use "chemical synthesis" to mean just a "direct combination reaction". In a direct combination reaction, two or more reactants combine to form a single product. The chemical equation for a direct combination reaction is:
where A and B are elements or compounds, and AB is a compound consisting of A and B. Examples of combination reactions include:
Four special synthesis rules are:
Organic synthesis
Organic synthesis is a special part of chemical synthesis. It builds organic compounds using organic reactions. Organic molecules can have a higher level of complexity compared to inorganic compounds. So, the synthesis of organic compounds has developed into one of the most important parts of organic chemistry. There are two main areas of research fields within the general area of organic synthesis: "total synthesis" and "methodology".
A total synthesis is the complete chemical synthesis of complex organic molecules from simple, commercially available (petrochemical) or natural precursors. In a "linear" synthesis—often used for simple structures—several steps are performed one after another until the molecule is complete. The chemical compounds made in each step are usually called "synthetic intermediates". For more complex molecules, a different approach may be preferable: convergent synthesis involves the individual preparation of several "pieces" (key intermediates), which are then combined to form the goal product.
Robert Burns Woodward, who received the 1965 Nobel Prize in Chemistry for several total syntheses (for example, his 1954 synthesis of strychnine), is regarded as the father of modern organic synthesis. Some latter-day examples of total synthesis include Wender's, Holton's, Nicolaou's and Danishefsky's synthesis of Taxol.
Each step of a synthesis involves a chemical reaction, and reagents and conditions for each of these reactions need to be designed to give a good yield and a pure product, with as little work as possible. A method may already exist in the literature for making one of the early synthetic intermediates, and this method will usually be used rather than "trying to reinvent the wheel". However most intermediates are compounds that have never been made before. These will normally be made using general methods developed by methodology researchers. To be useful, these methods need to give high yields. They must also be reliable for a broad range of substrates. For practical applications, additional requirements include industrial standards of safety and purity. Methodology research usually involves three main stages: "discovery", "optimization", and studies of "scope and limitations". The "discovery" requires extensive knowledge of and experience with chemical reactivities of appropriate reagents. "Optimization" is where one or two starting compounds are tested in the reaction under a wide variety of conditions of temperature, solvent, reaction time, etc. Researchers try different conditions until they find the best conditions for product yield and purity. Finally, researchers try to extend the synthesis method to a broad range of different starting materials, to find its scope and limitations. Total synthesis (see above) are sometimes used to highlight the new method and demonstrate its value in a real-world application. Major industries focused especially on polymers (and plastics) and on pharmaceuticals have used this research.
Most complex natural products are chiral. Each enantiomer can have a different bioactivity. Traditional total syntheses targeted racemic mixtures, i.e., as an equal mixture of both possible enantiomers. The racemic mixture might then be separated via chiral resolution.