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    Home > Biochemistry News > Biotechnology News > The journal Nature found that white phosphorus is the correct "open" way to directly synthesize organic compounds

    The journal Nature found that white phosphorus is the correct "open" way to directly synthesize organic compounds

    • Last Update: 2020-06-07
    • Source: Internet
    • Author: User
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    Want to come to our junior high school when we were exposed to white phosphorus, when the demonstration experiment is white phosphorus in the presence of air rapid combustion, resulting in a large number of white smoke, the chemical equation is as followswhite phosphorus is a white or light yellow translucent solid, the fire point is low (about 40 degrees C)Even if the surrounding environment is below 40 degrees C, the heat generated by friction, impact or slow oxidation can cause local temperatures to reach the point of ignition, which can trigger "spontaneous combustion"White phosphorus burns to produce a rare green flame, and sharply heat, the composition of white smoke is phosphorus pentoxide (P2O5), the actual structure is P4O10 (P2O5 is the result of the simplification of the points, the actual does not exist)the properties of white phosphorus (photo source: BXXXD (CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/))some of the spy agents in the film take out an "unidentified" escape weapon, and a heavy smoke is involved in the chemical effect when they fall to the groundTo this end, white phosphorus can be used in the military field to make smoke screen bombs, incendiary bombsAccidental exposure to white phosphorus can cause severe burns, burns of more than 7% of the area can cause acute hemolytic anemia, and even acute renal failureOf course, P2O5 is also highly corrosive, its moisture absorption is strong, can be used as an acid desiccant, and water reaction can form phosphoric acid, and further heatThe author remembers that before the distillation of acetic acid when adding P2O5 as a desiccant, accidentally inhaled very little, the next day due to throat mucosal edema caused by sound losshowever, the power of burning is small compared to the toxicity of white phosphorusThe death rate of white phosphorus is only about 50 mg, and the human body's intake of white phosphorus will cause serious corrosion effect on the gastrointestinal tractThe toxicology of phosphorus poisoning has not been conclusively determined, it is generally believed that white phosphorus has fattening, it is easy to enter the blood through the cell membrane of the digestive tract, accumulated in the liver, through its free radical species damage liver cells, once the degree of damage exceeds the liver's own repair capacity, can cause liver failureIn a short period of time a large intake of white phosphorus can be due to systemic bleeding, blood nausea, blood and circulatory system failure to die, vomit can be glowing in the dark, long-term inhalation of phosphorus vapor can lead to bronchitis, pneumonia and even jaw necrosis, that is, "phosphorus chin." This phosphorous jaw necrosis symptom first appeared in 19th-century matchmaker workers, and interested readers can search for information on their ownrambling about the dangers of so much white phosphorus, many readers may have begun to talk about "phosphorus" color changeHowever, white phosphorus is produced worldwide at an annual capacity of more than 1 million tons and can be used to produce a range of phosphorus-containing compounds, such as phosphoric acid, and is an important chemical raw materialThis double-edged sword good and evil coexist, can play a role, depends on phosphorus, but also depends on people For example, the team of Professor Robert Wolf of the University of Regensburg in Germany took full advantage of the bright side of white phosphorus to efficiently convert white phosphorus into highly applicable triaraitic or the corresponding tetraaromatic-based season salts, induced by visible light The findings were published in Nature Catalysis, a sub-journal of Nature of the image source: reference materials, phosphorus has a variety of isomorphic bodies, common including white phosphorus, red phosphorus, black phosphorus, etc , of which white phosphorus is the most active reaction, the largest production of phosphorus monoculture The molecular formula of white phosphorus is P4, and the four P atoms form a covalent bond between each other, which is a positive tetrahexon structure theoretically, all phosphorus-containing compounds can be obtained from P4 through a specific reaction route, however, in most cases the reaction steps are more cumbersome, and involve the unnecessary conversion process, directly on P4 for the official preparation of a variety of phosphorus-containing compounds there is a great challenge For example, in the synthesis of the organic pyridine compound triaraphonic and the corresponding tetraaromatic-based salt, the reaction is P4 as raw material, need to be mixed with Cl2 to oxidize it as PCl3, PCl5, and then re-use the appropriate organic metal reagents (such as fangyge reagents, aromatic sodium reagents) for its pro-nuclear replacement The process of net reaction does not involve the introduction of Cl atom, Cl atom came and went, from the point of view of atomic economics caused a great waste, but not using Cl2 can not complete the corresponding transformation, thus bringing "chicken ribs, abandoned, without gain" dilemma the method of synthesizing triaraphium in the past (image source: resources, 2) we mentioned above that each P atom in P4 and the other three P atoms respectively formed a covalent bond, a total of six groups of P-P covalent bonds, the first step of organic function conversion usually involves the fracture of multiple groups of P-P bonds, destroying the core structure of P4 skeleton and further forming C-P bonds It is not difficult to achieve this reaction process, in the past people have developed a variety of low oxidation state of transition metal conjums for catalytic activation of P4, some of the main family metallization (matching) compounds and unsaturated non-metallic compounds can also complete this transformation However, after activation can be controlled to carry out the official transformation is very difficult, especially for the synthesis of organic pyridine compounds, the reaction is usually low yield, selectivity is difficult to say In an earlier study, the team of Professor Derek H.R Barton of Texas A-M University, , found that the fatty ricacid was first converted into the corresponding thiodepyrite, which, when triggered by light, produced the corresponding carbon free radicals, and that P4 could be combined with it as a good carbon free radical capture agent and form the final alkyl acid product under the oxidation of H2O2 However, the P-atom utilization of P4 in the reaction is poor, and the conversion of a molecule of thiodeketoneest consumes a molecule P4, which means that the other three P atoms of P4 will be lost as by-products and cannot be used With the rapid development of photooxxidinalycinadaxial reactions, Professor Robert Wolf's team thought that it might be possible to design a P4-involved photoreacty process to transform into organic pyridine compounds At present, many photooxxiration catalytic reactions under the action of visible light, room temperature conditions can be smooth, photoxioxise catalyst in the excitation state and the substrate single electron transfer to form a corresponding free radical species, based on the results of Professor Derek H.R Barton's research, P4 can further react with the species Since strong oxidants or reductizers are not required during the reaction process, the P atoms in P4 may be fully utilized, thus achieving efficient conversion of P4 the photooxxiroxcatalytic catalysis P4 directly converted into triaragen and the corresponding four-aromatic nibsalt (photo source: reference source: 2) the author envisions the preparation of triaraphium or the corresponding tetraaromatic-based salt from P4, the most direct and simple solution is to directly mix halogen aromatic hydrocarbons with P4 to achieve the above process Halogen aromatic hydrocarbons can form the corresponding aromatic free radicalunder under the action of photooxxim catalyst, so that if this carbon free radical can be captured by P4, it is possible to complete the above transformation So, first, they took PhI as the template substrate, examined a series of photooxxim catalysts to participate in the reaction effect, and finally found that the selection of the "Ir( dtbbpy) (ppy) 2) PF6 (1) PF6, dtbbpy s 4,4'-two-shot-butyric-2,2'-biabolin, ppy - 2-2-2-zilki) benzene as the best catalyst for the catalytic effect Under the exposure of blu-ray LED, et3N is used as the quenching agent of the photooxxim catalyst excitation state, and finally can obtain the target product of The "Ph4P" and I-Target with good yield of 31P NMR (76%) and excellent selectivity All P atoms in P4 are involved in the araphinization process, which is used to the maximum extent When the reaction scale is large, this tetraaromatic-based salt can be separated and purified by recrystallization the optimization of the reaction conditions (photo source: resources 2) they also designed a blank control experiment, confirming that the photooxxim reduction catalyst s.1 When halogenated aromatic hydrocarbons were replaced with PhBr or PhCl with low reaction activity, there was no obvious production of argon salt products Without PhI, P4 can still be completely consumed, indicating that P4 can be reduced directly in the reaction system without the need for subsequent conversion stoics attached to the aromatic free radicals It also shows that this response is significantly different from the approach developed by Professor Derek H.R Barton in the past this method is suitable for a variety of different alternative base modifications of iodine-based aromatic hydrocarbons, benzene rings instead of absorption electron groups and electronic groups can be effectively involved in the reaction In most cases, the reaction forms a mixture of tetraaromatic salt and triaraty, which is later mainly separated by sublimation The background object that replaces the base modification of the adjacent part is less active by the influence of spatial bit resistance, and the reaction of some substrates participating in the reaction stays in the stage of single-aracy and di-fang-basedization In addition, since Ph3SnCl produces free radical Ph3Sn , it can also be mixed with P4 to efficiently form (Ph3Sn) 3P products the scope of application of the substrate (Image Source: Resource source, 2) further expansion of the scope of application of the substrate (Image Source: Resources 2) the author verified the mechanism of the reaction through a series of spectral analysis and electrochemical experiments Taking the substrate PhI as an example, Ir(III) photooxxim catalyst sipulating to the excitation state under visible light excitation, oxidizing Et3N and forming AnIr (II) reduced active species, the intermediate and PhI occurred single electron transfer to form benzene free radical Ph Et3N is oxidized after the form of the loss of an H-atom, forming ammonium salts ( Et2NC(H)Me - I- They also used time-to-time resolution of 31P.1H NMR analysis to confirm the existence of other phosphorus-containing intermediates in the reaction process, but it is not clear identification, P4 core skeleton structure of the P-P key fracture mechanism is not very clear the possible reaction mechanism of the crucive(Photo: Source: Reference s.) , Professor Robert Wolf's team took the first step in directly converting P4 catalysis into an organic pyridine compound Reaction sits no longer converts P4 into phosphorus chloride intermediates through a roundabout strategy, followed by subsequent officialization, which is of special significance from the perspective of basic research However, from the reaction results, there is still a lot of room for improvement in the application range of substrates, and the reaction mechanism still needs to be further fully verified The catalysis of photooxxim reduction provides a new idea for the activation of P4, and the future author will continue to expand the type of substrate (free radical precursor) to play the greater function of P4 References Retrieved Dec 11, 2019, from https:// 2, Ulrich Lennert et al., (2019) Direct catalytic molsan of white phosines y phosphium salts Nat Catal., DOI: 10.1038/s41929-019-0378-4 P4 by Late-Transition Activation Metales Complex Chem Rev., DOI: 10.1021/cr900349u P4 Activation by Main Group Elements and Compounds Chem Rev., DOI: 10.1021/cr100010e The invention of radical reactions Part 39 The reaction of white phous with carbon-centered radicals An improved procedure for the synthesis of phosphonic acids and the further mechanistic insights Tetrahedron Lett., DOI: 10.1016/S0040-4020 (98) 00729-7
    original title: "Nature" sub-issue: Finding the correct "open" way to find the deadly poison white phosphorus, direct synthesis of organic pyridine compounds
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