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Diễn đàn » Hóa học đại học và sau đại học » Tiếng Anh chuyên ngành hóa học (English for Special Purposes) » Lesson thirty six (Organic chemistry and history)

Lesson thirty six
ProfVietanhNgày: Thứ hai, 2010-05-31, 9:19 PM | Tin nhắn # 1
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Organic chemistry and history

Organic chemistry

Organic chemistry is a specific 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, halogens as well as phosphorus, silicon and sulfur.

The original definition of "organic" chemistry came from the misperception that organic compounds were always related to life processes. Not all organic compounds support life on Earth, but life as we know it also depends heavily 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, inorganic chemistry deals only with simple carbon compounds, with molecular structures which do not contain carbon to carbon connections (its oxides, acids, carbonates, carbides, and minerals). This does not mean that single-carbon organic compounds do not exist (viz. methane and its simple derivatives). Biochemistry mainly deals with the chemistry of proteins (and other large biomolecules).

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 life processes.

The different shapes and chemical reactivities of organic molecules provide an astonishing variety of functions, like those of enzyme catalysts in biochemical reactions of live systems. The autopropagating nature of these organic chemicals is what life is all about.

Trends in organic chemistry include chiral synthesis, green chemistry, microwave chemistry, fullerenes and microwave spectroscopy.


Phạm Bá Việt Anh

Department of Analytical Chemistry
Faculty of Chemistry
Hanoi National University of Education
Mobile - Tel: (84) 943 919 789
 
ProfVietanhNgày: Thứ hai, 2010-05-31, 9:20 PM | Tin nhắn # 2
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Historical highlights

At the beginning of the nineteenth century chemists generally thought that compounds from living organisms were too complicated in structure to be capable of artificial synthesis from non-living things, and that a 'vital force' or vitalism conferred the characteristics of living beings on this form of matter. They named these compounds 'organic', and preferred to direct their investigations toward inorganic materials that seemed more promising.

Organic chemistry received a boost when it was realized that these compounds could be treated in ways similar to inorganic compounds and could be created in the laboratory by means other than 'vital force'. Around 1816 Michel Chevreul started a study of soaps made from various fats and alkali. He separated the different acids that, in combination with the alkali, produced the soap. Since these were all individual compounds, he demonstrated that it was possible to make a chemical change in various fats (which traditionally come from organic sources), producing new compounds, without 'vital force'. In 1828 Friedrich Wöhler first manufactured the organic chemical urea (carbamide), a constituent of urine, from the inorganic ammonium cyanate NH4OCN, in what is now called the Wöhler synthesis. Although Wöhler was, at this time as well as afterwards, cautious about claiming that he had thereby destroyed the theory of vital force, most have looked to this event as the turning point.
A great next step was when in 1856 William Henry Perkin, while trying to manufacture quinine, again accidentally came to manufacture the organic dye now called Perkin's mauve, which by generating a huge amount of money greatly increased interest in organic chemistry. Another step was the laboratory preparation of DDT by Othmer Zeidler in 1874, but the insecticide properties of this compound were not discovered until much later.

The crucial breakthrough for the theory of organic chemistry was the concept of chemical structure, developed independently and simultaneously by Friedrich August Kekule and Archibald Scott Couper in 1858. Both men suggested that tetravalent carbon atoms could link to each other to form a carbon lattice, and that the detailed patterns of atomic bonding could be discerned by skillful interpretations of appropriate chemical reactions.

The history of organic chemistry continues with the discovery of petroleum and its separation into fractions according to boiling ranges. The conversion of different compound types or individual compounds by various chemical processes created the petroleum chemistry leading to the birth of the petrochemical industry, which successfully manufactured artificial rubbers, the various organic adhesives, the property-modifying petroleum additives, and plastics.
The pharmaceutical industry began in the last decade of the 19th century when acetylsalicylic acid (more commonly referred to as aspirin) manufacture was started in Germany by Bayer.
Early examples of organic reactions and applications were serendipitous, such as Perkin's accidental discovery of Perkin's mauve. However, from the 20th century, the progress of organic chemistry allowed for synthesis of specifically selected compounds or even molecules designed with specific properties, as in drug design. The process of finding new synthesis routes for a given compounds is called total synthesis. Total synthesis of complex natural compounds started with urea, increased in complexity to glucose and terpineol, and in 1907, total synthesis was commercialized the first time by Gustaf Komppa with camphor.

Pharmaceutical benefits have been substantial, for example cholesterol-related compounds have opened ways to synthesis of complex human hormones and their modified derivatives. Since the start of the 20th century, complexity of total syntheses has been increasing, with examples such as lysergic acid and vitamin B12. Today's targets feature tens of stereogenic centers that must be synthesized correctly with asymmetric synthesis.

Biochemistry, the chemistry of living organisms, their structure and interactions in vitro and inside living systems, has only started in the 20th century, opening up a brand new chapter of organic chemistry with enormous scope.


Phạm Bá Việt Anh

Department of Analytical Chemistry
Faculty of Chemistry
Hanoi National University of Education
Mobile - Tel: (84) 943 919 789
 
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