The historical origin of chemistry is very old. It can be said that the earliest chemical practice began when humans learned to use fire. Our ancestors drilled wood for fire, roasted food with fire, kept warm in cold nights and drove away wild animals, making full use of the phenomena of light and heat during burning. At that time, it was just the accumulation of experience. The formation of chemical knowledge and the development of chemistry have gone through a long and tortuous road. It develops with the progress of human society and is the inevitable result of social development. Its development has promoted the development of productive forces and historical progress. The development of chemistry has mainly experienced the following periods:
From ancient times to BC 1500, humans learned to make pottery with clay, burn metal with ore, make wine with grain, and dye fabrics such as silk and flax with fire. These are the earliest chemical processes that have not formed chemical knowledge after a long period of exploration under the direct inspiration of practical experience, but they are just the embryonic stage of chemistry.
From about 1500 BC to 1650 AD, chemistry was controlled by alchemy and alchemy. In order to obtain immortal elixir or gold symbolizing wealth, alchemists and alchemists began the earliest chemical experiments, and then books recording and summarizing alchemy appeared one after another. Although both alchemists and alchemists ended in failure, in the process of refining elixir and exploring the method of "turning stone into gold", they realized the mutual transformation between substances by artificial methods, accumulated the conditions and phenomena of chemical changes of many substances, and accumulated rich practical experience for the development of chemistry. The word "chemistry" that appeared at that time meant "alchemy". However, with the decline of alchemy and alchemy, people have increasingly seen its absurd side, and chemical methods have been properly played in medicine and metallurgy. The development of pharmacy and metallurgy at home and abroad has prepared rich materials for chemistry to become a science.
This period, from 1650 to 1775, is the gestation period of modern chemistry. With the accumulation of metallurgical industry and laboratory experience, people sum up perceptual knowledge and make theoretical research on chemical changes, making chemistry a branch of natural science. British chemist Boyle pointed out the scientific concept of chemical elements, which marked the beginning of this stage. Then chemistry was liberated from alchemy by phlogiston. According to phlogiston theory, combustible can burn because it contains phlogiston, and the combustion process is the process in which combustible releases phlogiston. Although this theory is wrong, it unifies a large number of chemical facts under one concept and explains many chemical phenomena. During the more than one hundred years when phlogiston theory prevailed, chemists did a lot of experiments to explain various phenomena, discovered the existence of various gases, and accumulated more new knowledge about substance transformation. In particular, phlogiston theory holds that chemical reaction is a process of transferring one substance to another, and substances are conserved in chemical reaction, which lays the foundation of modern chemical thought. This period not only prepared for the development of modern chemistry in scientific practice, but also in thought, and became the gestation period of modern chemistry. This period, from 1775 to 1900, is a period of modern chemistry development. 1775 or so, lavoisier expounded the oxidation theory of combustion with quantitative chemical experiments, which initiated the period of quantitative chemistry and made chemistry develop along the right track. /kloc-At the beginning of the 9th century, British chemist Dalton put forward modern atomic theory, and then Italian scientist Avo Gardero put forward the concept of molecule. Since atomic and molecular theories were used to study chemistry, chemistry has really been established as a science. During this period, many basic laws of chemistry were established. Russian chemist Mendeleev discovered the periodic law of elements, while German chemists Justus von Liebig and Willer developed the theory of organic structure, which made chemistry a systematic science and laid the foundation for the development of modern chemistry.
This period basically started at the beginning of the 20th century and is a period of modern chemistry. At the beginning of the 20th century, the rapid development of physics and the appearance of various physical testing methods promoted the research in the fields of solution theory, material structure and catalysts, especially the development of quantum theory, which made chemistry and physics have more common languages, solved many unresolved problems in chemistry, and gradually improved the theories of physical chemistry and structural chemistry. At the same time, with the infiltration of chemistry into biology and geology, structural problems such as protein and enzymes, which were difficult to solve in the past, have been deeply studied, and biochemistry has developed rapidly.
Since chemistry became an independent discipline, chemists have created many new substances that do not exist in nature. By the beginning of the 20th century, human beings had discovered and synthesized more than 30 million substances, which enabled them to enjoy more advanced scientific achievements and greatly enriched their material life.
In recent years, the proposal of green chemistry has made more chemical production processes and products develop in an environmentally friendly direction, and chemistry will surely make the world more colorful.
It is true that the development of science is endless, so the development of chemistry will never stagnate.
The story of chemist Kekule/KLOC-0 was born in darmstadt in 1929, and/KLOC-0 studied architecture at Giessen University in 1947. Influenced by Justus von Liebig, he turned his attention to chemistry and worshipped Justus von Liebig as his teacher. /kloc-completed the doctoral thesis "amyl sulfate" in 0/850.
1850- 1856, following the advice of his tutor, he went to Paris to make extensive contact with type theory. He listened to the organic chemistry taught by Duma, read the manuscript of Monograph on Organic Chemistry just written by Charles Gerhardt and got to know Wu Ci. Kekule caught a glimpse of the present situation and theoretical confusion of organic chemistry.
/kloc-in the winter of 0/854, Kekule arrived in London and worked as Steinhaus's assistant in a hospital, where he met Williamson and Hoffman. They often got together to discuss the theoretical and philosophical issues of organic chemistry, which had a strong influence on young Kekule. As he later said, "I was originally a student in Justus von Liebig, then a student in Duma, Gé rard and Williamson, and now I don't belong to any school." 1858, he was a professor at Ghent University. Here (1866), he announced the structural formula of benzene, which made Kekule famous all over the world. From 65438 to 0867, he was employed as a professor at Bonn University and director of the Institute of Chemistry. He died from 65438 to 0896.
Kekule has made many important contributions to the establishment of organic chemical structure theory. For example:
(1) On the tetravalent theory of carbon and the hypothesis that carbon atoms can be linked into chains. 1850, the British chemist Frank Crane () found that in some organometallic molecules, each metal atom can only combine with a completely determined number of organic groups, which is called the valence of elements. Frank Rand's idea developed Kekule, and Kekule understood the true meaning of valence and took it as the dominant idea of his own organic molecular theory. Kekule proposed in 1857 that the most important element in organic compounds is tetravalent carbon. On this basis, the structural models of some compounds were designed. 1858, Kekule published "On the structure and metamorphosis of compounds and the chemical properties of carbon atoms", re-emphasizing that carbon atoms are tetravalent and suggesting that carbon atoms can form chains with each other. This hypothesis later became the basis of organic molecular structure theory, which has proved its correctness and reflected its objectivity. In the same year, the British chemist Cooper also put forward the hypothesis that carbon is tetravalent and carbon atoms can be connected into chains in his article "New Chemical Theory". After reading this paper, Kekule immediately wrote a paper, pointing out that the priority of confirming that carbon atoms are tetravalent and the possible formation of carbon chains should belong to Kekule. But he also pointed out that the molecules of organic compounds have certain structures, which can be expressed by structural formulas. This view should be attributed to Cooper.
(2) The structural formula of benzene was established. Benzene was discovered by Faraday in 1825. Kekule put forward the cyclic structure theory of benzene in 1865: "If we want to explain the composition of atoms in aromatic compounds, we must explain the following facts: ① All aromatic compounds, even the simplest compounds, contain more carbon than the corresponding compounds in aliphatic groups; (2) As in aliphatic, there are many homologues in aromatic; ③ The simplest aromatic compound contains at least 6 carbon atoms, which form a symmetrical ring, and there are single bonds or double bonds between carbon atoms; (4) All the derivatives of aromatic substances show some characteristics of the same family, and they all belong to' aromatic compounds'. After some fierce reactions, they often lose some carbon, but the main products still contain at least six carbon atoms unless the organic groups are completely destroyed. Otherwise, when these products containing at least 6 carbon atoms are formed, the decomposition will stop. "
In 1865, Kekule expressed the structural formula (I) of benzene with a hexagon. 1866, he drew a sketch of the space model of single and double bonds, which was later simplified as (3).
As for how Kekule discovered the structural formula of benzene, there are various accounts. For example, the form of atomic ring dance; There are six monkeys scratching at each other's paws or tails; The countess's ring was broken by her servant; Some are like patterns on Persian carpets; A snake said. As far as snakes are concerned, the records are different. Kekule recalled at the 1890 meeting to commemorate the 25th anniversary of the structural formula of benzene called Benzene Festival: "It would be interesting if you heard how the extremely rash association came into being in my mind." When I lived in London, I used to live in clapham Road near the House of Commons. I often go to Miao La, a friend who lives at the other end of the city, to spend the night together. We talked about all kinds of problems, most of which were about chemistry. On a sunny summer night, when the noisy city was asleep, I took the last long-distance bus back. As usual, I sat in the car and soon lost in thought. At this moment, my eyes saw the atoms spinning. The atom is always moving in my mind, but I can't see what it looks like. And this night, small atoms are always combined in pairs from time to time. Sometimes big atoms hold two small atoms, and big atoms catch three or four small atoms for a while, and then they all seem to form a whirlpool to waltz. I also saw the big atoms lined up and the small atoms at the other end of the chain were taken away. This is exactly the world that my teacher, master chemist Cobb, described with his charming style in his book Molecular World. I saw it all in front of him. It was not until the car attendant shouted "clapham Road is here" that I woke up from my fantasy. After returning to my apartment, I spent at least an hour writing this illusion this evening, and my structural theory was born. ""The same is true of the theory of the origin of benzene. When I lived in Gunn, Belgium, my study faced a narrow alley, and there was no sunlight coming in, so it was not inconvenient to work in the laboratory during the day. One night, I wrote "Chemistry Course", but my thoughts always turned to other issues from time to time, and the writing was not smooth. So I turned my chair to the fireplace and began to lick it. At this time, a group of atoms appeared in front of my eyes, and small atomic groups also appeared. I have experienced this illusion, and I am sensitive to it. I immediately distinguish between images of different shapes and sizes and long lines that have been densely combined many times. And these are like a group of snakes, intertwined and moving while rotating. Besides, I saw something, like a snake holding its tail, as if laughing at me and starting to spin. I woke up like an electric shock. This time, I spent the whole night sorting out this hypothesis. "There is a slightly different narrative in Morrison's Organic Chemistry. According to the above description, it shows that Kekule's mind is always haunted by the images of atoms and molecules, and he gets important enlightenment from hallucinations. This is because he studied architecture when he was young and was good at capturing intuitive images. He studied under Justus von Liebig, Duma, Williamson and other famous teachers, and did not belong to any school. He developed the habit of independent thinking, based on rich chemical facts, and conducted various analyses and discussions with a serious scientific attitude before he succeeded.
2.