Green chemistry

Green chemistry, also called sustainable chemistry, is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances. Whereas environmental chemistry is the chemistry of the natural environment, and of pollutant chemicals in nature, green chemistry seeks to reduce and prevent pollution at its source. In 1990 the Pollution Prevention Act was passed in the United States. This act helped create a modus operandi for dealing with pollution in an original and innovative way. It aims to avoid problems before they happen.
As a chemical philosophy, green chemistry derives from organic chemistry, inorganic chemistry, biochemistry, analytical chemistry, and even physical chemistry. However, the philosophy of green chemistry tends to focus on industrial applications. Click chemistry is often cited as a style of chemical synthesis that is consistent with the goals of green chemistry. The focus is on minimizing the hazard and maximizing the efficiency of any chemical choice. It is distinct from environmental chemistry which focuses on chemical phenomena in the environment.
In 2005 Ryoji Noyori identified three key developments in green chemistry: use of supercritical carbon dioxide as green solvent, aqueous hydrogen peroxide for clean oxidations and the use of hydrogen in asymmetric synthesis.Examples of applied green chemistry are supercritical water oxidation, on water reactions and dry media reactions.

Radiochemistry

Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable). Much of radiochemistry deals with the use of radioactivity to study ordinary chemical reactions.

Organic chemistry

Organic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting primarily of carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, the halogens as well as phosphorus, silicon and sulfur.
The original definition of "organic" chemistry came from the misconception that organic compounds were always related to life processes. However, organic molecules can be produced by processes not involving life. Life as we know it also depends on inorganic chemistry. For example, many enzymes rely on transition metals such as iron and copper; and materials such as shells, teeth and bones are part organic, part inorganic in composition. Apart from elemental carbon, only certain classes of carbon compounds (such as oxides, carbonates, and carbides) are conventionally considered inorganic. Biochemistry deals mainly with the natural chemistry of biomolecules such as proteins, nucleic acids, and sugars.
Because of their unique properties, multi-carbon compounds exhibit extremely large variety and the range of application of organic compounds is enormous. They form the basis of, or are important constituents of many products (paints, plastics, food, explosives, drugs, petrochemicals, to name but a few) and (apart from a very few exceptions) they form the basis of all earthly life processes.

Inorganic chemistry

Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compound. This field covers all chemical compounds except the myriad organic compounds (compounds containing C-H bonds), which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, and there is much overlap, most importantly in the sub-discipline of organometallic chemistry.

Medicinal Chemistry

Medicinal or pharmaceutical chemistry is a scientific discipline at the intersection of chemistry and pharmacology involved with designing, shyntesyzing and developing pharmaceutical drugs. Medicinal chemistry involves the identification, synthesis and development of new chemical entities suitable for therapeutic use. It also includes the study of existing drugs, their biological properties, and their (QSAR). Pharmaceutical chemistry is focused on quality aspects of medicines and aims to assure fitness for the purpose of medicinal products.
Compounds used as medicines are overwhelmingly organic products. However, metal-containing compounds have been found to be useful as drugs. For example, the cis-platin series of platinum-containing complexes have found use as anti-cancer agents. This type of compounds are known as metal-based drugs.
Medicinal chemistry is a highly interdisciplinary science combining organic chemistry with biochemistry, computational chemistry, pharmacology, pharmacognosy, molecular biology, statistics, and physical chemistry.

Chemical engineering

Chemical engineering is the branch of engineering that deals with the application of physical science, with mathematics, to the process of converting raw materials or chemicals into more useful or valuable forms. In addition to producing useful materials, chemical engineering is also concerned with pioneering valuable new materials and techniques, an important form of research and development. A person employed in this field is called a chemical engineer.
Chemical engineering largely involves the design and maintenance of chemical processes for large-scale manufacture. Chemical engineers in this branch are usually employed under the title of process engineer.

Geochemistry

The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and their interaction with the hydrosphere and the atmosphere.

The most important fields of geochemistry are:

1. Isotope geochemistry: Determination of the relative and absolute concentrations of the elements and their isotopes in the earth and on earth's surface.
2. Examination of the distribution and movements of elements in different parts of the earth (crust, mantle, hydrosphere etc.) and in minerals with the goal to determine the underlying system of distribution and movement.
3. Cosmochemistry: Analysis of the distribution of elements and their isotopes in the cosmos.
4. Biogeochemistry: Field of study focusing on the effect of life on the chemistry of the earth.
5. Organic geochemistry: A study of the role of processes and compounds that are derived from living or once-living organisms.
6. Regional, environmental and exploration geochemistry: Applications to environmental, hydrological and mineral exploration studies.