|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
MOST IMPORTANT SCIENTIFIC DISCOVERIES
Theory of chemical structure. History and essence of scientific discovery
Directory / The most important scientific discoveries At the beginning of the nineteenth century, the Davy-Berzelius electrochemical theory reigned supreme among Western chemists. According to the theory of Jens Berzelius (1779–1848), two parts of each chemical compound were distinguished: one part charged electropositively, the other electronegatively charged. Accordingly, Berzelius arranged all the elements in a row, with oxygen being the most electronegative element, potassium the most electropositive. Berzelius called the most electronegative elements metalloids, the most electropositive - metals. In the thirties, with his work, the French chemist J. B. Dumas dealt a blow to the theory of Davy - Berzelius, putting forward his so-called theory of types for organic compounds. Dumas argued that not so much the nature of a complex body as the arrangement of atoms in it, the same type, determine the chemical properties of the compound. However, these views of Dumas soon ran into a whole series of difficulties and contradictions. Subsequently, a huge step forward in the problem of the development of basic chemical concepts was the so-called unitary system, or theory of the French chemists Ch. Gerard and O. Laurent. The most essential feature of this theory was the consistent application of the new doctrine to chemical compounds. Laurent and Gerard are credited with distinguishing between the concepts of particle, atom and equivalent. However, the most fundamental issue that caused heated debates among the leading chemists of the West was the question of the possibility of expressing the structure of chemical compounds by formulas. The great reformer of chemistry, as Charles Frédéric Gérard (1816-1856) was sometimes called, became convinced that chemical phenomena begin only when matter changes, i.e., ceases to exist as such. Therefore, we can know, as Gerard put it, only the past and future of matter, and, consequently, chemical formulas can express not the arrangement of atoms, but only known analogues of substances. In accordance with what has just been said, according to Gerard, for each substance one can write as many rational formulas as the given substance can undergo various types of transformations. In 1858 the famous chemist August Kekule (1829–1896) takes an extremely important step and extends the concept of carbon four atoms to compounds containing several carbon atoms, and thus comes to the conclusion that it is possible to expediently link carbon atoms in polycarbon compounds. In the future, this rule of coupling Kekule extends to the cases of combination of carbon atoms with other polyatomic elements, such as, for example, oxygen, nitrogen, and others. Later, Kekule came close to the problem of the structure of organic compounds, having as a starting point the atomicity or valency of the elements, but did not take a decisive step in this direction. So, at the end of his article in 1858, Kekule writes: “In conclusion, I consider it necessary to note that I myself attach only secondary importance to arguments of this kind ...” It should be added to the above that Kekulé remained for a long time in the grip of Gerard's ideas and in his well-known textbook of organic chemistry, published in 1859-1861, he makes extensive use of "rational" formulas in the spirit of Gerard. And although the approach of a new period in the development of chemistry was felt, Butlerov's genius was needed to make a breakthrough. Alexander Mikhailovich Butlerov (1828–1886) was born in Butlerovka, a small village near Kazan, where his father's estate was located. Sasha did not remember his mother, she died eleven days after his birth. Raised by his father, an educated man, Sasha wanted to be like him in everything. At first he studied at a boarding school, and then entered the First Kazan Gymnasium. After graduating, Sasha entered the natural science department of Kazan University, however, so far only as a student, he was still a minor. Only the following year, 1845, when the young man turned 17, Butlerov's name appeared on the list of those accepted for the first year. In 1846, the young man fell ill with typhus and miraculously survived, but his father, who had contracted it, died. In autumn, together with my aunt, they moved to Kazan. Young Butlerov studied with exceptional zeal, but, to his surprise, he noticed that lectures on chemistry gave him the greatest pleasure. He started attending lectures regularly. Nikolai Nikolaevich Zininwhich were read for students of the Physics and Mathematics Department. To receive a candidate's degree, Butlerov had to submit a dissertation upon graduation from the university. By this time, Zinin left Kazan for St. Petersburg, and there was nothing left but to do natural sciences. For the candidate's work, Butlerov prepared an article "Daytime butterflies of the Volga-Ural fauna". However, the circumstances were such that Alexander still had to return to chemistry. In the fall of 1850, Butlerov passed the exams for a master's degree in chemistry and immediately began his doctoral dissertation "On Essential Oils", which he defended at the beginning of the next year. On June 4, 1854, Butlerov received confirmation that he had been awarded the degree of Doctor of Chemistry and Physics. Events unfolded with incredible speed. Immediately after receiving his doctorate, Butlerov was appointed acting professor of chemistry at Kazan University. At the beginning of 1857, he already became a professor, and in the summer of that year he received permission to travel abroad. Butlerov arrived in Berlin at the end of the summer. He then continued to tour Germany, Switzerland, Italy and France. The ultimate goal of his journey was Paris - the world center of chemical science of that time. He was attracted, first of all, by a meeting with Adolf Würz. Butlerov worked in the Wurtz laboratory for two months, it was here that he began his experimental studies, which over the next twenty years were crowned with the discoveries of dozens of new substances and reactions. Numerous exemplary syntheses of Butlerov - ethanol and ethylene, dinzobutylene, tertiary alcohols, urotropine, trioxymethylene, polymerization of ethylene hydrocarbons - lie at the origins of a number of industries and, thus, had the most direct stimulating effect on it. While studying hydrocarbons, Butlerov realized that they represent a very special class of chemicals. Analyzing their structure and properties, the scientist noticed that there is a strict pattern here. It formed the basis of the theory of chemical structure he created. On February 17, 1858, Butlerov made a report at the Paris Chemical Society, where he first outlined his theoretical ideas about the structure of matter. His report aroused general interest and lively debate: “The ability of atoms to combine with each other is different. Particularly interesting in this respect is carbon, which, according to August Kekule, is tetravalent,” Butlerov said in his report. not notice that the method of connection is reflected in the properties of the corresponding compounds. No one has yet expressed such thoughts. “Perhaps the time has come,” Butlerov continued, “when our research should become the basis of a new theory of the chemical structure of substances. This theory will be distinguished by the accuracy of mathematical laws and will make it possible to predict the properties of organic compounds.” A few years later, during a second trip abroad, Butlerov presented the theory he had created for discussion. He made the announcement at the 36th Congress of German Naturalists and Physicians in Speyer. The convention took place in September 1861. He made a presentation before the chemical section. The topic had a more than modest name - "Something about the chemical structure of bodies." In the report, Butlerov expresses the main provisions of his theory of the structure of organic compounds. This is, first of all, the definition of the concept of "chemical structure", which Butlerov formulates as follows: "Proceeding from the idea that each chemical atom, which is part of the body, takes part in the formation of this latter and acts here with a certain amount of chemical force (affinity) belonging to it, I call the chemical structure the distribution of the action of this force, due to which chemical atoms, mediately or directly influencing each other, combine into a chemical particle. “This definition of Butlerov is so deep,” writes Academician A.E. Arbuzov in his book, “so meaningful that basically it does not differ from what we currently mean by chemical structure in the light of the latest scientific ideas about the structure of a chemical particle (molecules). Extremely important, especially for that time, is also the place in the report where Butlerov speaks of the possibility of judging the structure of the molecules of a substance by chemical methods and, above all, by methods for the synthesis of organic compounds. On this issue, Butlerov says in his report: “Conclusions about the chemical structure of substances, in all likelihood, can best be based on the study of the methods of their synthetic formation - and mainly on such syntheses that are performed at a temperature that is slightly elevated and - in general - at conditions where one can follow the course of the gradual complication of a chemical particle. However, the most important place in Butlerov's report is the question of the possibility of expressing the structure of a substance by formulas. On this fundamental issue, Butlerov's scientific position differed sharply from the views and convictions of all his predecessors. It was AM Butlerov, in contrast to Gerard, Kekula, Kolbe and other chemists, who considered it possible and necessary to express the structure of a certain compound with only one formula. that Butlerov is the true creator of the theory of chemical structure". So, the theory has declared its right to exist. It required further development and experimental evidence. In 1863, Butlerov, acting on acetyl chloride with dimethylzinc, obtained for the first time in the history of chemistry the simplest tertiary alcohol - tertiary butyl alcohol, or trimethylcarbinol. Shortly thereafter, reports appeared in the literature about the successful synthesis of primary and secondary butyl alcohols. Now there was no question of any dispute - there were four different butyl alcohols. And they are all isomers. What a triumph for structural theory! And how happy was its author. The triumph of Butlerov's theory of the chemical structure of organic compounds was the correct explanation based on this theory of the phenomena of isomerism. In the article "On Various Ways of Explaining Some Cases of Isomerism", published in 1863 in German and in 1864 in French, Butlerov concluded: "If, with the same composition, substances differ in properties, then they must also differ in their chemical structure." The best confirmation of Butlerov's theory of isomerism was the synthesis of theoretically predicted isomers - isobutane and isobutylene. In 1862–1865, Butlerov expressed the main position of the theory of reversible isomerization - tautomerism, the mechanism of which, according to Butlerov, is the splitting of molecules of one structure and the combination of their residues to form molecules of another structure. Success brought confidence to the scientist, but at the same time presented him with a new, more difficult task. It was necessary to apply the structural theory to all reactions and compounds of organic chemistry, and most importantly, to write a new textbook on organic chemistry, where all phenomena would be considered from the point of view of a new theory of structure. Butlerov worked on the textbook for almost two years without a break. The book "Introduction to the Complete Study of Organic Chemistry" was published in three editions in 1864-1866. The appearance of this textbook was of great importance for the dissemination of the new doctrine among chemists. The book caused a real revolution in chemical science. Already in 1867, work began on its translation and publication in German. The publication by Butlerov in Russian and German of a manual on organic chemistry, where for the first time the theory of chemical structure was consistently carried through all the then known classes of organic compounds, along with his brilliant syntheses, contributed to the wide recognition and strengthening of his theory among chemists around the world. Shortly thereafter, editions appeared in almost all major European languages. According to the German researcher Victor Meyer, it has become "a guiding light in the vast majority of research in organic chemistry." In his research, Butlerov continued to develop the structural theory. He set out to prove that all types of organic compounds can have branched and straight carbon chains. This followed directly from the theory, but the theoretical propositions had to be proved in practice. Is it not possible to obtain a hydrocarbon - for example, butane - whose four carbon atoms would be connected to each other not sequentially, but in the way they are connected in trimethyl-carbinol? But to find the right method for its synthesis, many experiments were required. And finally, Butlerov's efforts were crowned with success. In a large flask was the long-awaited isobutylene. The existence of a branched chain of hydrocarbons has been proven! Today, by the way, the production of hydrocarbons and alcohols, which Butlerov was engaged in, has reached a colossal industrial scale, they are produced in millions of tons. Author: Samin D.K.
▪ Benzene
Artificial leather for touch emulation
15.04.2024 Petgugu Global cat litter
15.04.2024 The attractiveness of caring men
14.04.2024
▪ New Intel Pentium 4 processor ▪ Explay Atom 3 SIM Smartphone ▪ Holes in the light tied in knots
▪ section of the site Electronic directories. Article selection ▪ article Alteration of the washing machine for low water pressure. Tips for the home master ▪ article What is a quarry? Detailed answer ▪ article Aralia high. Legends, cultivation, methods of application ▪ reference generator article. Encyclopedia of radio electronics and electrical engineering
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
We recommend interesting articles Section 
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page