CHEMISTRY

From Big Medical Encyclopedia

HYMIYa (srednevek. Arab al-kimiya; Greek chymeia and chemeia art of alloyage of metals) — the field of natural sciences studying a structure and properties of chemical elements (atoms) formed by them simple and complex substances (molecules), transformation of substances (connections) and the laws which are the cornerstone of these phenomena. Chemical transformations (reactions) are caused by electronic interactions of elements and happen without change of atomic nuclei (see. Chemical changes).

The chemistry as area of knowledge is connected with studying of chemical form of motion of matter and its transitions to other forms of motion that is expressed in versatility of chemistry and its versatile bonds with other sciences, first of all with physics and biology (see). The chemistry makes a big contribution to the doctrine about development of the nature, in deepening of materialistic ideas of the universe.

The modern chemistry plays an important role in life of human society, being one of powerful factors of economic, scientific and technical and cultural progress. Bonds of chemistry with medicine and health care are diverse.

The chemistry forms a basis of such major sections of biology and medicine as biochemistry (see), physiology (see), pharmacology (see), etc. also some new disciplines, naira, bioinorganic chemistry, a molecular psychobiology. The role of chemistry in research of pharmaceuticals is traditional that is historically connected with a yatrokhimiya (see). The chemistry gained special development in 20 century as a result of the achievements of organic chemistry which provided progress of anesthesiology (see), resuscitation (see), to pharmacotherapy (see), etc. The modern synthetic chemistry and biochemical technology created a huge arsenal of chemotherapeutic means, antibiotics, vitamins, hormones, alkaloids and various supporting materials. Achievements of modern surgery in noticeable degree are caused by achievements of the polymer chemistry which created various materials for prosthetics, tools, medical glues, artificial blood substitutes, etc. Are widely used, especially in oncology, various marked connections (see) received by radiochemical methods. Achievements of analytical chemistry (see) promoted creation of reagents and development of methods of the analysis and diagnosis in clinical biochemistry (see), a histochemistry (see), immunochemistry (see) and other areas.

The subject of chemistry makes a huge circle of the substances, the phenomena and processes studied by means of various methods therefore the modern chemistry represents a number of the interconnected scientific disciplines. Traditionally the chemistry is divided into the inorganic chemistry (see) studying chemical elements and the simple and complex substances formed by them (except carbon compounds), and the organic chemistry (see) which is engaged in studying of carbon compounds with other elements. Between inorganic and organic chemistry the elementoorganichesky chemistry is intermediate; biopolymer substances fall within the scope of studying of bioorganic chemistry. Interpenetration of chemistry and other sciences led to development of a number of scientific disciplines, napr, physical chemistry (see) and chemical physics; the general for chemistry and biology of a problem study biochemistry (see) and molecular biology (see); as boundary disciplines between chemistry and geology arose geochemistry (see), and also biogeochemistry (see). Due to the studying of the organization of substance at various structural levels such independent disciplines as chemistry of complex connections, polymer chemistry, a crystal chemistry, colloid chemistry were created (see) etc. The analytical chemistry, methods a cut is of great importance for all sections of chemistry are applied in the most various areas, including in biology and medicine. As practical applications of chemistry developed chemical technology with its many industries, agrochemistry, etc.

Laws and other theoretical provisions of chemistry are formulated by means of mathematics, edges is necessary also for experimental chemistry. The fixed methodical assets in chemistry are the analysis, i.e. decomposition of complex substances on simpler (up to elements), and synthesis, or receiving complex substances from simpler, including and from elements. These methods serve as universal ways of studying of structure, a structure and properties of substances and receiving chemical connections. In chemistry also large number of experimental methods and auxiliary receptions is developed for carrying out reactions, cleaning and the characteristic of substances, etc. Chemical formulas and the equations of reactions are applied to the image of chemical connections, their transformations, structural and electronic representations in chemistry.

The chemical phenomena used for practical purposes already in the ancient time (Egypt, Mesopotamia, India, China, the Mediterranean) at production of ceramics, smelting of metals, dyeing, preparation of drugs, etc. In antique Greece initial doctrines about atoms and elements elements arose. In the Middle Ages there was an alchemy — the mystical doctrine setting as a main goal transformation of basic metals into gold and silver by means of a so-called philosophers' stone. In Renaissance the alchemy got a big practical orientation (for mining, metallurgy, glassblowing, etc.) also there was special, its medical direction — a yatrokhimiya (see). Despite delusions of alchemists, by them it was saved up many facts promoting emergence of scientific chemistry (discovery of new substances, development of methods of their allocation and cleaning).

In the second half of 17 century R. Boyle showed insolvency of alchemical representations and gave the first scientific definition of a chemical element. Thereby the chemistry was for the first time lifted to the level of science. At the beginning of 18 century the first, though wrong, chemical theory (phlogiston theory) was formulated. Its denial and further formation of chemistry were promoted opening of the law of conservation of weight (mass) of substances by M. V. Lomonosov (1748) at chemical reactions,

A. Lavoisier's creation of the oxygen theory is later than the confirmed A. Lavoisier, and. Development of chemistry in 19 century is characterized by creation of its theoretical bases, first of all the atomic molecular theory [J. Dalton, A. Avogadro, I. Bertselius, etc.], opening of the major laws, accumulation of extensive experimental material. The first theories about the nature of chemical substances (electrochemical, the theory of radicals, unitary, the theory of types) which played a certain role in development of inorganic and organic chemistry were put forward. Formation of structural representations in chemistry was promoted by introduction in the 50th 19 century of a concept of valency (see). The theory of a chemical structure created by A. M. Butlerov (1861) laid the foundation of modern organic chemistry. Opening of many chemical elements resulted in urgent need of their systematization. Therefore a fundamental event in chemistry were opened by D. I. Mendeleyev (1869) the Periodic Table (see) and the periodic law which became a basis of further development of chemistry. During the research of the general patterns of chemical processes, in process of development of physics and chemistry, a number of the new concepts and laws which formed a basis for creation of physical chemistry with its many sections was established and also to colloid chemistry. Achievements of biology and organic chemistry led to formation of biochemistry. Development of theoretical bases of chemical processes promoted development of chemical technology and the chemical industry. Thus, by the end of 19 century there were main sections of chemistry.

Outstanding opening of physics at the end of 19 century (the phenomenon of radioactivity, x-ray emission, an electron) laid the foundation for a new stage in development of chemistry, led to essentially new ideas of a structure and properties of matter. The theory of an atomic structure developed at the beginning of 20 century (see) formed a basis for deeper theoretical justification of the periodic law. Further development of chemistry happened on the basis of incessantly improved theoretical concepts about an atomic structure, communication of physical and chemical properties of elements with a structure of electron shells of atoms. There were new ideas of the nature of chemical forces, the first electronic theories of valency and chemical bonds are offered. Emergence of quantum-mechanical representations (see. The quantum theory) allowed to explain the nature of chemical communication, advanced the chemical theory on new level, having led to creation of quantum chemistry.

The modern chemistry is characterized by profound studying of chemical processes, kinetics and mechanisms of reactions (see Kinetics chemical, Chemical changes), penetration into an essence of elementary acts of chemical interaction. In a crust, time in chemistry mathematical methods and electronic computer facilities are intensively used. Various spectral methods of a research became the integral line of experimental chemistry: electron, infrared and X-ray spectroscopy, spectroscopy of a nuclear magnetic and electronic paramagnetic resonance, gamma-resonant spectroscopy, etc. (see Spectroscopy). An important role in a chemical research is played the X-ray crystallographic analysis (see), a mass spectrometer iya (see), by an elektronografiya, a polyarografiya (see), different types of a chromatography (see), studying of reactions by means of radioisotopes and many other methods.

Differentiation of the main partitions into a number in many respects of independent areas is characteristic of the modern chemistry having very extensive circle of objects of studying (naira., chemistry of rare earth elements, chemistry of lipids, etc.). Along with traditional sections of chemistry the electrochemistry, photochemistry, a radiochemistry, etc. gained big development, the new fields of chemistry, napr, plasma chemistry, a kosmokhimiya, etc. were created. Achievements of modern synthetic chemistry, especially considerable in the field of organic synthesis are high. An important role is played by modern chemistry in the applied researches necessary for development of chemical technology and promoting chemicalixation of the national economy. Treat receiving substances with the set valuable properties the main tendencies of modern chemical technology, development progressive tekhnol. processes and creation of wasteless chemical productions for the purpose of preservation of the environment and reasonable regulation of the processes happening in it.

Studying of the main sections of chemistry (the general, inorganic, organic, physical, colloid, analytical) is an obligatory element of system of training of specialists in medical averages and higher educational institutions.

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A. I. Tochilkin.

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