Organic Chemistry is also calledcarbonizationComplexChemistry, is researchOrganic compoundComposition, structure, property, preparation method and application ofscience, is a very important branch of chemistry.Carbonaceous compounds are calledMechanizationBecause chemists in the past believed that such substances must be produced by living things（Organism）Talent manufacturing;However, in 1828, German chemistsFriedrich Wohler , successfully synthesized urea (a kind ofBiomolecule）Since then, organic chemistry has broken away from the traditional definition and expanded to the chemistry of hydrocarbons and their derivatives.
The term "organic chemistry" was first used byBezerius("the father of organic chemistry").It was named as the antithesis of "inorganic chemistry" at that time.Due to scientific conditions, the object of organic chemistry research can only be fromnaturalOrganic matter extracted from animal and plant organisms.Therefore, many chemists believe that organic compounds can only be produced due to the existence of the so-called "vitality" in the organism, while inorganic compounds cannot be synthesized in the laboratory.[1]
In 1824, German chemistWeilerPrepared from cyanide by hydrolysisoxalate；In 1828, he unintentionally converted ammonium cyanate into urea by heating.Cyanide andAmmonium cyanateBoth are inorganic compounds, while oxalic acid and urea are organic compounds.Weiler's experimental results give the first impact to the theory of "vitality".Since then, organic compounds such as acetic acid have been successively synthesized from elements such as carbon and hydrogen,Vitality theoryWas gradually abandoned by people.
Due to the improvement and development of synthesis methods, more and more organic compounds are synthesized in the laboratory, most of which are synthesized under different conditions from those in the organism.The theory of "vitality" has been abandoned gradually, but the term "organic chemistry" has been still used today.[1]
From the beginning of the 19th century to 1858, before the concept of valence bond was put forward, it was the embryonic period of organic chemistry.During this period, many organic compounds have been separated, some derivatives have been prepared, and they have been qualitatively described, and the properties of some organic compounds have been recognized.
Lavoisier
French chemist Lavoisier found that after the combustion of organic compoundscarbon dioxideAnd water.His research work is organic compound elementquantitative analysisLaid the foundation.1830 German chemistLiebig Developed carbon and hydrogenanalytical methodIn 1833, the French chemist Duma established the nitrogen analysis method.These are organicQuantitative analysis methodThe establishment of the system enables chemists to obtain the experimental formula of a compound.
At that time, great difficulties were encountered in solving the problem of how the atoms in organic compound molecules were arranged and combined.At first, organic chemistry used dualism to solve the structural problems of organic compounds.Dualism holds that the molecule of a compound can be divided into the part with positive charge and the part with negative chargeElectrostatic forceTogether.According to some chemical reactions, early chemists believed that organic compound molecules were formed byGroupIt is combined with the group that changes in reaction according to electrostatic force of the anisotropic charge.But this theory itself has great contradictions.
The typology was established by French chemists Gerald and Laurent.This theory denies that organic compounds are composed of groups with positive and negative charges, but believes that organic compounds are derived from some parent compounds that can be replaced, so they can be classified according to these parent compounds.Type theory classifies many organic compounds into different types. According to their types, it can not only explain some properties of compounds, but also predict some new compounds.However, typology fails to answer the structural problem of organic compounds.This problem has become a mystery that has puzzled people for many years.[2]
Period of classical organic chemistry
From the establishment of valence bond theory in 1858 to the introduction of valence bond electronic theory in 1916, this mystery was solved. This period is the period of classical organic chemistry.
Kekule
In 1858, German chemistKekule He put forward the concept of valence bond with British chemist Cooper, and for the first time used a short dash "-" to indicate "bond".They believe that organic compound molecules are formed by the combination of their constituent atoms through bonds.Since of all known compounds, onehydrogen atomHydrogen is chosen as the unit of valence when it can only be combined with atoms of an individual element.The valence number of an element is the number of hydrogen atoms that can combine with one atom of the element.Kekule also proposed the important concept that carbon atoms in a molecule can combine with each other.
In 1848, Pasteur separated twotartaric acidCrystallization, one half face crystal is left, and the other half face crystal is right.The former can makePlane polarized lightRotate to the left, and the latter makes it rotate to the right at the same angle.Similar phenomena were encountered in the study of lactic acid.For this reason, in 1874, French chemist Lebel and Dutch chemist Van Toff put forward a new concept: isomer, which successfully explained theIsomerism。[2]
They believe that the molecule is a three-dimensional entity, and the four valence bonds of carbon are symmetrical in space, pointing to oneRegular tetrahedronThe carbon atom is located at the center of the tetrahedron.When a carbon atom is connected with four different atoms or groups, a pair of isomers will be producedmaterial objectandimage, or the chiral relationship between the left hand and the right hand, the pair of compounds are mutually optically active isomers orEnantiomer。This phenomenon is calledEnantiomerismPhenomenon.These two molecules, which are physical and mirror images of each other, are enantiomeric but not completely coincident, and are called chiral molecules.The theories of Lebel and Vantov are the basis of stereochemistry in organic chemistry.[3]
In 1900, the first free radical, triphenylmethyl radical, was found, which is a long-lived free radical.The existence of unstable free radicals was also confirmed in 1929.
During this period, organic compounds have made great progress in structural determination, reaction and classification.However, valence bond is only a concept that chemists draw from practical experience, and the essence of valence bond has not been solved yet.[2]
Modern Organic Chemistry Period
French biochemist Louis Pasteur
On the basis of physicists discovering electrons and clarifying the atomic structure, American physical chemist Louis et al. put forward the electronic theory of valence bond in 1916.
They believe that the interaction of the outer electrons of each atom is the reason for the combination of atoms.If the interacting outer electrons are transferred from one atom to another, an ionic bond is formed;If two atoms share outer electrons, they formcovalent bond。Through the transfer or sharing of electrons, the outer electrons of the interacting atoms are all obtained from the inert gasElectronic configuration。Thus, the dash "-" used to represent the valence bond in the image representation of the valence bond is actually a pair of two atomsShared electron pair。[4]
After 1927, Heitler and London used quantum mechanics to deal with the problem of molecular structure and establishedValence bond theoryA mathematical model for chemical bond is proposed.Later, Maliken usedMolecular orbital theoryTo deal with the molecular structure, the results are generally consistent with those obtained from the electronic theory of valence bonds. Because of the simple calculation, many questions that could not be answered at that time were solved.[4]
Chemical research
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Research object
There is no absolute boundary between organic compounds and inorganic compounds.The reason why organic chemistry has become an independent discipline in chemistry is that organic compounds do have their inherent connections and characteristics.
The carbon element in the periodic table is generally stabilized by sharing the outer electrons with the atoms of other elementsElectronic configuration(that is, to form a covalent bond).The combination mode of this covalent bond 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, nitrogen and other elements.Therefore, most organic compounds have low melting point, can be burnedSolubleIt is quite different from the properties of inorganic compounds in terms of organic solvents and other properties.
In organic compound molecules containing multiple carbon atoms, carbon atoms combine with each other to form a molecular skeleton, and atoms of other elements are connected to the skeleton.stayperiodic table of ele mentsThere is no other element that can combine firmly with each other in many ways like carbon.The molecular skeleton formed by carbon atoms has many forms, including straight chainBranched chain, ring, etc.
In the early development of organic chemistry,Organic chemical industryIts main raw materials are animals and plants. Organic chemistry mainly studies the separation of organic compounds from animals and plants.
From the middle of the 19th century to the beginning of the 20th century, the organic chemical industry gradually turned to coal tar as the main raw material.Synthetic dyesThe discovery ofAromatic compoundandHeterocyclic compoundResearch.After the 1930s, organic synthesis with ethylene as raw material rose.Around the 1940s, the raw materials of organic chemical industry gradually changed to oil and natural gas, and developedsynthetic rubber、Synthetic plasticsAnd synthetic fiber industry.becauseoil resources The organic chemical industry based on coal will be developed again.Of course, natural animals, plants and micro organisms are still important research objects.
To summarize the research object of organic chemistry in the most concise sentence, it is "how to form carbon carbon bond".Organic chemistry is the chemistry of carbon. The content of organic chemistry is to study how to build a building (or small building) of carbon atoms.Because the organic molecules useful to people are generally large and complex, while the raw materials that people can freely dispose of and easily obtain are often small and simple.[3]
research findings
Natural Organic ChemistryThe composition, synthesis, structure and properties of natural organic compounds are mainly studied.From the early 20th century to the 1930smonosaccharide, amino acidnucleotide、Bovine cholic acidStructure of cholesterol and some terpenes, composition of peptides and proteins;In the 1930s and 1940s, we determined the structure of some vitamins, steroid hormones and polysaccharides, and completed the research on the structure and synthesis of some steroid hormones and vitamins;In the 1940s and 1950s, some antibiotics such as penicillin were discovered, and structural determination and synthesis were completed;In the 1950s, someSteroidTotal synthesis of alkaloids such as morphine, oxytocin, etcbiological activitySmall peptideThe chemical structure of insulin was determined, the helical structure of protein and the double helical structure of DNA were found;In the 1960s, he completed the total synthesis of insulin and the synthesis of oligonucleotides;From the 1970s to the early 1980sprostaglandin、Vitamin B12、Insect pheromoneThe total synthesis of hormones determines the structure of nucleic acid and medellin and completes their total synthesis.
Organic synthesisIt mainly studies the synthesis of organic compounds from simpler compounds or elements through chemical reactions.Urea was synthesized in the 1930s;Acetic acid was synthesized in 1940s.Later, they successively synthesizedGluconic acid, citric acidSuccinic acid, malic acid and other organic acids;In the second half of the 19th century, a variety of dyes were synthesized;In the 1940s, DDT andOrganophosphorus insecticide、Organic sulfur bactericide, herbicides and other pesticides;At the beginning of the 20th century, 606 medicaments were synthesized. In the 1930s and 1940s, more than 1000 sulfonamides were synthesized, some of which can be used as drugs.
research method
The development of organic chemistry research means has gone through a process from manual operation to automation, computerization, and from constant to ultramicro.[5]
Before 1940s, traditional distillation, crystallization, sublimation and other methods were used to purify the product, and chemical degradation and derivative preparation methods were used to determine the structure.Later, various chromatographic and electrophoretic techniques were applied, especiallyHigh pressure liquid chromatographyThe application of GIS has changed the face of separation technology.Various spectraEnergy spectrumThe use of technology enables organic chemists to study the internal movement of molecules and revolutionizes the means of structure determination.With the introduction of electronic computers, the separation and analysis methods of organic compounds have taken another big step towards automation and ultramicro quantification.With Fourier transform technologyNuclear magnetic resonance spectrumAnd infrared spectrumreaction kineticsThe study of reaction mechanism provides a new means.These instruments and X-ray structural analysis, electron diffractionspectral analysisThe chemical structure of microgram sample can be determined.Some progress has also been made in the study of designing synthetic routes with computers.The development of organic chemistry in the future is first to study the development and utilization of energy and resources.So far, most of the energy and resources we use, such as coal, natural gas, oil, animals, plants and microorganisms, are chemical storage forms of solar energy.In the future, the important subject of some disciplines is to use solar energy more directly and effectively.[5]
It is a common subject of plant physiology, biochemistry and organic chemistry to do more in-depth research and effective use of photosynthesis.Organic chemistry can use photochemical reaction to generate high-energy organic compounds for storage;Use it when necessaryReverse reaction, release energy.Another goal of developing resources is toOrganometallic compoundUnder the action ofFixed carbon dioxideTo produce endless organic compounds.Some preliminary results have been obtained from these studies.Secondly, research and develop new organic catalysts to enable them toMimetic enzymeHigh speed, high efficiency and mild reaction mode.The research in this field has begun and will have greater development in the future.At the end of the 1960s, the research on computer-aided design of organic synthesis began.In the future, the design of organic synthesis routes and the determination of the structure of organic compounds will become more systematic and logical.[5]
More essentially, there are only two types of reactions: nucleophilic and electrophilic substitution, because addition reaction can be regarded as a special substitution.
Advanced Classification:
According to the mechanism, organic reactions can be divided into four categories:
Ionic reaction, including all categories classified in the above entry version.
Free radical reaction, characterized by no ions involved, the controllable degree of the reaction is generally low, and it has not been fully developed.
Organometallic reaction, organometallic reaction is essentially a combination of the three reactions mentioned above, but it has its particularity in some places, so it is a separate category.
Curriculum system
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Organic chemistry mainly introduces the science of chemical substances (some organic chemistry courses will also be involved in high school chemistry study).The classification of organic chemical substances is mainly based on their decisive role, the groups that can represent chemical substances, that is, functional groups.It can be divided into: alkanes, alkenes, alkynes, aromatic hydrocarbons (above are hydrocarbons);Halohydrocarbon, alcohol, phenol, ether, aldehyde, ketone, carboxylic acid,carboxylic acid derivatives , Amines,Nitro compound, nitriles,SulfurOrganic compounds (such as mercaptans,Thioether, thiophenol, sulfonic acid, sulfone andSulfoxideEtc.), phosphorus containing organic compounds, etcElemental organic compounds, heterocyclic compounds, etc. (the above are hydrocarbon derivatives).
It mainly introduces the systematic naming, chemical reaction, reaction mechanism and preparation methods of these chemicals.The chemical reaction is basicallyGroupWhether a reaction can be carried out depends on both thermodynamic and kinetic factors.The preparation method is mainly to prepare difficult to obtain substances through inorganic substances, petroleum extracts, and easily prepared or low-cost substances.The reaction mechanism is also the competition between the attacking and leaving tendencies of groups.
