The term "organic chemistry" was first put forward by Betzerius in 1806. It was named the opposite of "inorganic chemistry" at that time. Due to the limitation of scientific conditions, the research object of organic chemistry can only be organic matter extracted from natural animal and plant organisms. Therefore, many chemists believe that organic compounds can only be produced because of the so-called "vitality" in organisms, and cannot be synthesized by inorganic compounds in the laboratory.
1824, German chemist Willer hydrolyzed cyanide to oxalic acid. 1828, he accidentally heated ammonium cyanate into urea. Cyanide and ammonium cyanate are inorganic compounds, while oxalic acid and urea are organic compounds. Wheeler's experimental results gave the "vitality" theory its first impact. Since then, organic compounds such as acetic acid have been synthesized from carbon, hydrogen and other elements, and the theory of "vitality" has been gradually abandoned by people.
Due to the improvement and development of synthetic methods, more and more organic compounds are synthesized in the laboratory, and most of them are synthesized under completely different conditions from living organisms. The theory of "vitality" was gradually abandoned, but the term "organic chemistry" has been used to this day.
From the beginning of 19 century to 1858, before the concept of valence bond was put forward, organic chemistry was in its infancy. During this period, many organic compounds were separated, some derivatives were prepared and described qualitatively, and the properties of some organic compounds were recognized.
French chemist lavoisier found that after burning organic compounds, carbon dioxide and water will be produced. His research work laid the foundation for the quantitative analysis of organic compounds. 1830, German chemist Justus von Liebig developed the analysis method of carbon and hydrogen, 1833, French chemist Duma established the analysis method of nitrogen. The establishment of these organic quantitative analysis methods enables chemists to obtain the experimental formula of a compound.
At that time, great difficulties were encountered in solving the problem of how to arrange and combine atoms in organic compounds. At first, organic chemistry used binary theory to solve the structural problems of organic compounds. Binary theory holds that molecules of compounds can be divided into positively charged parts and negatively charged parts, which are combined by electrostatic force. According to some chemical reactions, early chemists believed that the molecules of organic compounds were composed of groups that remained unchanged in the reaction and groups that changed in the reaction according to the electrostatic force of opposite charges. But this theory itself has great contradictions.
French chemists Gé rard and Laurent established the type theory. This theory denies that organic compounds are composed of positively charged and negatively charged groups, but thinks that organic compounds are derived from some parent compounds that can be substituted, so they can be classified according to these parent compounds. Typology divides many organic compounds into different types. According to their types, we can not only explain some properties of compounds, but also predict some new compounds. However, the type theory fails to answer the structural questions of organic compounds. This problem has become a mystery that has puzzled people for many years.
From the establishment of valence bond theory in 1858 to the introduction of valence bond electron theory in 19 16, this puzzling mystery was solved. This period is the period of classical organic chemistry.
1858, German chemist Kekule and British chemist Cooper put forward the concept of valence bond, and used the dash "-"to represent "bond" for the first time. They believe that the molecules of organic compounds are formed by the combination of their constituent atoms. Because in all known compounds, one hydrogen atom can only combine with the atom of another element, so hydrogen is chosen as the price unit. The valence of an element is the number of hydrogen atoms that can combine with an atom of this element. Kekule also put forward an important concept, that is, carbon atoms in molecules can be combined with each other.
In 1848, Pasteur separated two kinds of tartaric acid crystals, one is the left semi-crystal and the other is the right semi-crystal. The former can rotate plane polarized light to the left, and the latter can rotate it to the right by the same angle. A similar phenomenon has been encountered in the study of lactic acid. Therefore, in 1874, Lebel, a French chemist, and Vantoff, a Dutch chemist, respectively put forward a new concept: isomer, which satisfactorily explained this isomerism.
They think that the molecule is a three-dimensional entity, the four valence bonds of carbon are symmetrical in space, pointing to the four vertices of a regular tetrahedron, and the carbon atom is located in the center of the regular tetrahedron. When carbon atoms are connected to four different atoms or groups, a pair of isomers are produced, which are the physical objects and mirror images of each other, or the chiral relationship between left and right hands. This pair of compounds is the optical isomers of each other. Lebel and Fantoff's theory is the basis of stereochemistry in organic chemistry.
The first free radical, triphenylmethyl radical, was found in 1900, which is a long-lived free radical. 1929 also confirmed the existence of unstable free radicals.
During this period, great progress has been made in the structural determination, reaction and classification of organic compounds. However, valence bond is just a concept that chemists get from practical experience, and the essence of valence bond has not been solved.
In the period of modern organic chemistry, on the basis of physicists' discovery of electrons and elucidation of atomic structure, American physical chemist Lewis and others put forward the valence bond electron theory in 19 16.
They believe that the interaction of electrons in the outer layer of atoms is the reason why atoms are bound together. If the interacting outer electrons are transferred from one atom to another, an ionic bond is formed; If two atoms use outer electrons, they form a valence bond. Through electron transfer or * * * utilization, the outer electrons of the interacting atoms all obtain the electron configuration of the inert gas. In this way, the dash "-"used to represent the valence bond in the valence bond diagram is actually a pair of electrons used by two atoms.
After 1927, Hai and London used quantum mechanics to solve the problem of molecular structure, established the valence bond theory and put forward the mathematical model of chemical bond. Later, Maliken used molecular orbital theory to deal with molecular structure, and the results obtained were basically consistent with those obtained by valence bond electron theory. Because of the simple calculation, many questions that could not be answered at that time were solved.
Second, the research content of organic chemistry
There is no absolute boundary between organic compounds and inorganic compounds. Organic chemistry has become an independent discipline in chemistry because organic compounds do have their internal relations and characteristics.
Generally, carbon elements in the periodic table form a stable electronic configuration (i.e., valence bond) with atoms of other elements by using outer electrons. This valence bond combination determines the characteristics of organic compounds. Most organic compounds are composed of carbon, hydrogen, nitrogen and oxygen, and a few also contain halogen, sulfur, phosphorus and nitrogen. Therefore, most organic compounds have the properties of low melting point, flammability and easy solubility in organic solvents, which are quite different from inorganic compounds.
In an organic compound molecule containing multiple carbon atoms, carbon atoms combine with each other to form the skeleton of the molecule, and atoms of other elements are connected to the skeleton. In the periodic table of elements, no other element can be firmly combined with each other in many ways like carbon. The molecular skeleton formed by carbon atoms has many forms, such as straight chain, branched chain, cyclic and so on.
In the early stage of the development of organic chemistry, the main raw materials of organic chemistry industry were animals and plants, and organic chemistry mainly studied the separation of organic compounds from animals and plants.
/kloc-from the middle of the 0/9th century to the beginning of the 20th century, the organic chemical industry gradually turned to coal tar as the main raw material. The discovery of synthetic dyes has made the dye and pharmaceutical industries flourish, and promoted the study of aromatic compounds and heterocyclic compounds. After 1930s, organic synthesis with acetylene as raw material rose. Around the 1940s, the raw materials of organic chemical industry gradually changed to oil and natural gas, and the industries of synthetic rubber, synthetic plastics and synthetic fibers developed. With the depletion of petroleum resources, organic chemical industry with coal as raw material will surely develop again. Of course, natural animals, plants and microorganisms are still important research objects.
Natural organic chemistry mainly studies the composition, synthesis, structure and properties of natural organic compounds. From the early 20th century to the 1930s, the structures of monosaccharides, amino acids, nucleotide cholic acid, cholesterol and some terpenoids, as well as the composition of peptides and protein were determined one after another. In 1930s and 1940s, the structures of some vitamins, steroid hormones and polysaccharides were determined, and the structures and synthesis of some steroid hormones and vitamins were studied. In the 1940s and 1950s, some antibiotics, such as penicillin, were discovered, and their structures were determined and synthesized. In 1950s, the total synthesis of some alkaloids such as steroids and morphine, and the synthesis of bioactive peptides such as oxytocin were completed. The chemical structure of insulin was determined, and the spiral structure of protein and the double helix structure of DNA were discovered. In 1960s, the total synthesis of insulin and oligonucleotide was completed. From 1970s to early 1980s, prostaglandins, vitamin B 12 and insect pheromones were all synthesized, and the structures of nucleic acids and maytansinone were determined and their total synthesis was completed.
Organic synthesis mainly studies the synthesis of organic compounds from simple compounds or elements through chemical reactions. Urea was synthesized by 19 in 1930s. Acetic acid was synthesized in the 1940s. Subsequently, a series of organic acids such as gluconic acid, citric acid, succinic acid and malic acid were synthesized one after another. /kloc-a variety of dyes were synthesized in the second half of the 0/9 century; Pesticides such as DDT, organophosphorus pesticides, organosulfur fungicides and herbicides were all synthesized in the 1940s. At the beginning of the 20th century, 606 kinds of drugs were synthesized, and in the 1930s and 40s, 1000 kinds of sulfonamides were synthesized, some of which can be used as medicine.
Physical organic chemistry is a subject that quantitatively studies the structure, reactivity and reaction mechanism of organic compounds. It is developed on the basis of valence bond electron theory, and cites the new progress of modern physics, physical chemistry and quantum mechanics theory. From 1920s to 1930s, a new organic chemistry system was established by studying the reaction mechanism. Conformation analysis and Hammett equation in 1950s began to estimate the relationship between reactivity and structure semi-quantitatively. The conservation of molecular orbital symmetry and frontier orbital theory appeared in the 1960s.
Organic analysis is the qualitative and quantitative analysis of organic compounds. The quantitative analysis method of carbon and hydrogen was established in 1930s of 19. Quantitative analysis of nitrogen was established in 1990s. The constant analysis of various elements in organic compounds was basically completed at the end of 19; In the 1920s, a quantitative analysis method of organic trace was established. Automated analytical instruments appeared in the 1970s.
Due to the development of science and technology, organic chemistry and other disciplines have infiltrated each other, forming many branches and marginal disciplines. Such as bioorganic chemistry, physical organic chemistry, quantum organic chemistry and marine organic chemistry.
Third, the research methods of organic chemistry
The development of research methods of organic chemistry has gone through the process from manual operation to automation and computerization, from constant to ultra-trace.
Before1940s, the product was purified by traditional distillation, crystallization and sublimation, and its structure was determined by chemical degradation and derivative preparation. Later, the application of various chromatography and electrophoresis technologies, especially the application of high pressure liquid chromatography, changed the face of separation technology. The use of various spectrum and energy spectrum techniques enables organic chemists to study the internal motion of molecules and revolutionizes the means of structure determination.
With the introduction of computer, the separation and analysis methods of organic compounds have taken a big step towards automation and ultramicro-quantification. The combination of nuclear magnetic resonance spectrum and infrared spectrum with Fourier transform technology provides a new means for studying the reaction kinetics and mechanism. These instruments, together with X-ray structure analysis and electron diffraction spectrum analysis, have been able to determine the chemical structure of microgram samples. Some progress has also been made in the research of designing synthetic routes with electronic computers.
The development of organic chemistry in the future is to study the development and utilization of energy and resources first. Up to now, most of the energy and resources we use, such as coal, natural gas, oil, animals and plants and microorganisms, are chemical storage forms of solar energy. The important subject of some disciplines in the future is to use solar energy more directly and effectively.
Further study and effective utilization of photosynthesis is a common subject of plant physiology, biochemistry and organic chemistry. Organic chemistry can generate high-energy organic compounds through photochemical reactions and store them; Use its reverse reaction to release energy if necessary. Another goal of developing resources is to fix carbon dioxide under the action of organometallic compounds and produce endless resources. Organic compounds. Some preliminary results have been achieved in these aspects.
Secondly, new organic catalysts were developed to simulate the high-speed, high-efficiency and mild reaction mode of enzymes. The research in this field has already started, and there will be greater development in the future.
In the late 1960s, the research on computer-aided design of organic synthesis began. In the future, the design of organic synthesis route and the determination of organic compound structure will be more systematic and reasonable.
Four. Organic chemistry course
Organic chemistry is mainly the science of introducing chemical substances (high school chemistry study will also involve some organic chemistry courses). At present, the classification of organic chemicals is mainly based on their decisive role, which can represent different groups of chemicals, that is, functional groups. Can be divided into: alkanes, alkenes, alkynes, aromatic hydrocarbons (above hydrocarbons); Halogenated hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, carboxylic acid derivatives, amines, nitro compounds, nitriles, sulfur-containing organic compounds (such as thiols, thioethers, thiophenols, sulfonic acids, sulfones and sulfoxides), phosphorus-containing organic compounds and other organic compounds, heterocyclic compounds, etc. (The above are hydrocarbon derivatives).
This paper mainly introduces the systematic nomenclature, chemical reactions, reaction mechanisms and preparation methods of these chemicals. Chemical reaction is basically the substitution of groups, and whether a reaction can be carried out depends on two factors: thermodynamics and kinetics. The preparation method mainly uses inorganic substances, petroleum extracts, substances that are easy to prepare or have low cost to prepare substances that are difficult to obtain. The reaction mechanism is also the competition between group attack and leaving tendency.