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MOST IMPORTANT SCIENTIFIC DISCOVERIES
organic synthesis. History and essence of scientific discovery
Directory / The most important scientific discoveries In 1834, T. Pelouse prepared cyanide alkyls by the action of potassium cyanide on alkyl sulfate salts. In the same year, J. B. Dumas was able to establish that formic acid is formed from chloroform under the action of caustic potassium. Thus, Dumas discovered a general method for obtaining acids by hydrolysis of halogen derivatives. In 1842, L. Melzens proposed a method for the reduction of halogen derivatives with alkali metal amalgams. Five years later, Zh.B. Dumas, F. Malaguti, F. Leblanc, E. Frankland, and G. Kolbe in 1848 proposed a general method for obtaining acids from compounds with a lower carbon content through nitriles. At the same time, E. Mitcherlich became the first chemist to use a mixture of concentrated nitric and sulfuric acids to obtain nitrobenzene from benzene. J. Liebig and F. Wöhler observed the transition of benzaldehyde to benzoic acid in the presence of alkali in 1832, and in 1853 S. Cannizzaro established that the corresponding alcohol is formed in this case. It is worth noting the discovery of the phenomenon of catalytic oxidation of alcohols and carbohydrates into acids in the presence of platinum black. These and other examples testified to the achievements in the field of production and transformations of organic compounds. With increasing confidence it was possible to speak about the possibility of organic synthesis. “In 1854, G. Kolbe pointed out,” writes E.P. Nikulina, “that after the synthesis of urea, the natural boundary separating organic and inorganic compounds fell, and the previous classification of substances into organic and inorganic, based on the impossibility of artificially obtaining the former, lost its basis ". A new stage in the development of organic synthesis is associated with the name of Berthelot. “The study of Berthelot’s work in the field of organic synthesis showed,” Nikulina continues, “that he plays a significant role in the development of this area of organic chemistry. Before Berthelot’s work, synthesis did not exist as an independent branch of organic chemistry. Separate methods were developed by various chemists, but these achievements were not linked into a single system. Berthelot himself assessed the activities of his predecessors as follows: “Before the work described in my book Organic Chemistry Based on Synthesis (1860), not a single systematic study had been carried out in this direction. Only two examples of the complete synthesis of natural substances from elements can be given. : the synthesis of Wöhler's urea and the synthesis of Kolbe's acetic acid. These syntheses are extremely interesting, but due to the very nature of these substances, they remained isolated and without consequences. Indeed, urea belongs to the cyan series, a series that belongs almost equally to inorganic and organic chemistry and which has no properties in common with other series, including neither alcohols nor hydrocarbons.Acetic acid also occupies a special place; until new experiments and new methods developed after 1860, this acid remained "an isolated body in the series organic compounds "(J. B. Dumas). The history of science also confirms that these two syntheses have not laid the foundation for any general method, and have not even led to any other partial synthesis of natural substances. With regard to partial syntheses, Berthelot noted that individual successful syntheses performed before him did not lead to an awareness of the importance of the problem of synthesis as a whole. Marcelin Berthelot (1827–1907) was born and raised in Paris in a poor medical family. At the Lyceum he was one of the best students. The next step in his studies is the College de France, where he listens to lectures by Claude Bernard, Antoine Jerome Balard, Michel Eugene Chevrel and other prominent scientists. In the autumn of 1848, Berthelot successfully passed the exam for a bachelor's degree and entered the university. After much hesitation, on the advice of his parents, Berthelot began to study medicine. However, the classes did not satisfy him, he felt the need for broader knowledge. At the end of the first academic year, he becomes a licentiate in physics. At the same time, Marselin began to study chemistry as one of the main disciplines in the general training of doctors. In the end, he decided to find a chemical laboratory in which he could gain experience as an experimenter. Jules Peluso's new private chemical laboratory became such a laboratory. Berthelot enthusiastically embarked on research work. After a while, he becomes Peluso's assistant. Berthelot began his first studies, which, since he was mainly engaged in physics, were more of a physical nature than concerned the field of chemistry. He was attracted by the phenomena associated with the liquefaction of gases. The young scientist published the results of his research in 1850. Over the course of six decades, Berthelot wrote about 2800 scientific papers, covering almost all branches of human knowledge. Most of these materials were works on chemistry, in addition, he wrote works on biology, agricultural chemistry, history, archeology, linguistics, philosophy, pedagogy, etc. Berthelot from the very beginning deeply believed in the possibility of the synthesis of organic substances without the participation of living cells. Along with scientific work in the laboratory, Berthelot regularly attended lectures at the College de France, where one could learn about the latest achievements of science. Professor Antoine Balard, drawing attention to the abilities of the young Berthelot, invited him to work at the laboratory of the College de France. The first success was the production of camphor, but the real success came to the scientist in 1853. Berthelot succeeded in synthesizing fat. Berthelot's article made a real sensation in the scientific world. The Paris Academy of Sciences praised this achievement. Berthelot was awarded the degree of Doctor of Physical Sciences. Berthelot sets himself a more difficult task - to obtain ethyl alcohol from ethylene and water. To do this, he decides to pass ethylene through an aqueous solution of an acid or base. Here is what K.R. writes about this. Manolov: "The first experiments did not give the desired results. Ethylene passed through the solution without causing any noticeable changes. Eertlo changed the synthesis conditions in every possible way. When conducting an experiment with concentrated sulfuric acid, he noticed that at a temperature of about 70 degrees Celsius, intensive absorption of ethylene began. After after the reaction, the scientist diluted the reaction mixture with water and subjected it to distillation. Ethyl alcohol! The distillate was ethyl alcohol. Berthelot was truly happy. He chose the right path. Organic substances in principle are no different from inorganic and can be obtained in the same way. It is necessary that scientists were convinced that no "life force" exists, that a person can direct the course of chemical reactions at will. But this still had to be proved, facts were needed ... And Berthelot continued to work ... " In the sixties of the nineteenth century, Berthelot achieves truly fantastic results in the field of organic synthesis. Failure did not bother him. The reaction of interaction of hydrogen with carbon could not be carried out even in Deville furnaces. Then Berthelot resorts to electricity. “Electric sparks did not solve the problem,” notes Manolov, “but the electric arc between two carbon electrodes in a vessel with hydrogen turned out to be effective: the gas leaving the vessel contained acetylene. Encouraged, Berthelot began a new series of syntheses. Adding hydrogen to acetylene, he got ethylene, and then ethane. “The ratio of carbon and hydrogen in acetylene is the same as in benzene,” thought Berthelot, and this thought prompted the young scientist to take up the synthesis of benzene. “This will bridge the gap between fatty and aromatic compounds.” For the synthesis, Berthelot decided to again resort to high temperatures and repeat the experiment as he had done to obtain carbon monoxide. A glass retort was filled with acetylene, sealed, and gradually heated. Only at a temperature of 550–600 degrees Celsius did acetylene begin to polymerize. When the retort was cooled, a small amount of a yellowish liquid collected at its bottom. Now all that was needed was patience and perseverance in order to carry out the experiment dozens of times and collect enough liquid for analysis. Berthelot found benzene, toluene and other aromatic compounds in the resulting liquid. In parallel, he carried out another synthesis, which also confirmed that aromatic compounds can be obtained from fatty hydrocarbons. Berthelot subjected methane to prolonged heating in special glass vessels. He raised the temperature so much that the glass began to soften. After cooling, a white crystalline substance formed in the vessels. As soon as the scientist opened the vessel, the laboratory was filled with the characteristic smell of naphthalene. Additional studies confirmed that the resulting substance is indeed naphthalene. A new series of syntheses and analyzes began. Ideas were born, and almost every day a new synthesis was carried out. It seemed that the possibilities were endless, Berthelot could synthesize everything, it was enough just to set the task correctly... ... Berthelot achieved great success in the study of hydrocarbons, carbohydrates, alcoholic fermentation; he proposed a universal method for the reduction of organic compounds with hydrogen iodide and much more. For outstanding achievements in organic chemistry in 1867, Berthelot received the Jacqueur award for the second time. Seven years ago, the first award was given to him for his achievements in the field of organic synthesis." The most important synthetic works of Berthelot can be divided into three groups. The first is the synthesis of natural compounds - fats, mustard oil. The second group - elemental syntheses of the simplest organic substances. The third one is pyrogenic syntheses of hydrocarbons. In addition, Berthelot managed to develop methods for the hydrogenation of organic compounds of various classes with hydrogen iodide. He also investigated the properties and obtained various derivatives of many organic compounds. In addition, Berthelot studied the processes of their oxidation and reduction. In 1860-1864, Berthelot decided to summarize his own numerous synthetic studies, as well as the work of other chemists, in the books Organic Chemistry Based on Synthesis and Lectures on General Synthetic Methods in Organic Chemistry. E.P. Nikulina describes his creative searches as follows: “M. Berthelot considered obtaining more complex substances by combining two simpler ones, or partial synthesis, as the first step towards complete synthesis. The implementation of such a synthesis is the closest consequence of an analytical study, since the analysis of a natural substance often shows the possibility of its decomposition into two simpler parts, which, when combined, give the original substance ... M. Berthelot believed that analysis and synthesis are two sides of chemical science, and emphasized that synthesis became possible precisely thanks to the success of analysis, since it is possible to synthesize only those substances that could be analytically decomposed into components from which they can again be obtained, or completely decompose by successive splitting off of elements, following the example of the "combustion ladder". In this regard, the impossibility of synthesizing at that time many natural substances, such as proteins and alkaloids, he explained by the fact that they were not yet well studied analytically, that is, the limit of synthesis, according to Berthelot, is determined by the possibilities of analysis. Today, synthesis is the basis of industrial chemistry. Suffice it to name synthetic rubber, synthetic fibers, synthetic fuels, synthetic detergents. Author: Samin D.K.
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