When we run out of diazomethane here, we always add some acid to destroy the remaining diazomethane. A buddy was bold enough to use concentrated hydrochloric acid (dilute hydrochloric acid or acetic acid) directly, and the result was a violent exothermic reaction with residual alkali. Diazomethane's ether solution ~ ~ ~ conquered him and exploded. Another teacher just didn't apply vacuum grease to the plug of the separatory funnel, but wiped it and burned the ether. It was terrible.
When using diazomethane, you must pay attention to it. It is best to have experienced guidance for the first time. Don't do it yourself, and the amount should not be too large. Don't be greedy for more than 25 grams of nitrosomethylurea. If you need a large quantity, do it in several batches.
Be careful when using ether in summer. I extracted it with ether in August this year. I just shook it gently in the separatory funnel and it was about to deflate. It was bombed, but it didn't hurt me. My product! ! !
Once I carry out liquid separation and extraction, I wash the organic phase (including the product) with 50 ml of HCl, and then wash the product with 50 ml of 5% NaHCO3. As a result, the plug was washed away as soon as it was shaken, and all the products were sprayed out. The reason is that there is no deflation.
Be careful when washing products. If washing will produce gas, be sure to pay attention to deflation.
Just this week, two major safety accidents occurred in our hospital in one day. A doctoral student used peracetic acid without wearing protective glasses. As a result, peracetic acid splashed on his eyes, causing eye injuries, so that he can't open them now. I wonder what will happen in the future. Another doctoral student accidentally got it when using triethylaluminum. Because I didn't wear protective gloves, I didn't wash it with a lot of water immediately after the accident. As a result, his left hand was badly skinned and needed skin grafting.
The two accidents have one thing in common: carelessness and failure to observe safety rules. If you wear protective glasses and gloves, the consequences will not be so serious. Moreover, the data shows that the more doctoral students there are, the less cautious they are in doing experiments. I always take chances and think that nothing will happen. As a result, everyone who could swim drowned in the river.
During my five years in the institute, I have heard and witnessed many safety accidents, and I feel more careful and secure. Now I know the potential dangers of the laboratory as follows: Welcome to add what you know.
First of all, the potential dangers of solvent treatment.
First, the solvent must be pretreated before anhydrous treatment.
For solvents with low boiling point, such as ether, n-pentane, etc., it is necessary to dry with desiccant in advance, and then add sodium wire to reflux, and the heating should not be too fast or too high. Because, once the water content in the solvent is too large, if hydrogen is produced violently, the solvent will easily rush out of the system and then explode when it meets an open flame or a heating resistance wire. This is a precedent in organic factories. The tragic situation at that time was that the shock wave of the explosion rushed from the third floor to the top floor, smashing the ventilation device. Including the entire window of the opposite laboratory, was knocked open.
For ether solvents, if they are produced or not used for a long time, they must not be shaken evenly. At the same time, reducing agents should be added to remove the generated peroxides. He is also a doctoral student. When he was dealing with a device for treating THF that had not been used for a long time, the grinding piston exploded as soon as it was pulled out, and his face was covered with blood.
The solvent treated with sodium and the haloalkane solvent treatment device cannot share a device connected to the atmosphere. In order to save trouble or space, some students connect all solvent treatment devices to ensure that they are connected to the atmosphere. The danger of this is that if the temperature of haloalkane, especially dichloromethane, is high when heated, it is likely not to condense. In this way, it is possible for haloalkane with higher density to enter the solvent system dried with sodium wire along the same pipeline. Once such a thing happens, it must be an explosion. As we all know, the coupling reaction of alkyl halides under the action of sodium metal is very intense.
B, waste solvent treatment, absolutely don't happen acidic liquid and alkaline liquid, oxidizing liquid and reducing liquid mixing, it is very dangerous. In the organic laboratory, the explosion of waste barrels is not once or twice. For SOCl2, PCl5, PCl3 _ 5 and PCL _ 3, they must not be put into the waste bucket without treatment, and the consequences are also very dangerous.
Second, the potential danger of experimental operation.
1, for the reaction of heating and gas production, we must be careful not to become a closed system.
2. You should be careful about the reaction of dripping cold, and you must strictly abide by it. Don't try to save trouble.
3, before the reaction, be sure to check whether there is any crack on the instrument. Generally, people will pay attention to the reaction in which the pressure of the reaction system changes greatly. However, some problems arise when you don't expect them. Once when I was extracting, the volume was about 2 liters and I found a crack in the separatory funnel. I thought there was no problem. As a result, I shook it in my hand and it exploded. 20% KOH solution was sprayed on my face, and even more frightening, the solution entered the socket along the desktop, causing a short circuit of power supply, which led to a fire.
4. For explosive reactants, such as peroxy compounds, azides, diazo compounds, anhydrous high-temperature salts, etc., be careful when using them, heat them carefully, measure them carefully, and handle them carefully. Don't explode because of vibration. Three examples are as follows:
When an associate professor was studying in the Institute of Organic Studies, he distilled a compound that was easily decomposed under pressure. Because the heating was not well controlled, an explosion occurred and the scene was extremely bloody. More than 50 stitches in the chest!
When a graduate student did an experiment on oxygen compounds, he concentrated the solution containing peroxide compounds with a rotary evaporator. After that, he did not put in the air carefully, but immediately ventilated it. Results Due to the impact of air, it caused explosion, Grade A and Grade A disability. The scene photo we saw today is: a finger stained with blood on the glass. (This is why pressurized distillation ventilation should be done slowly. )
A staff member makes azides in the laboratory and handles all the reactions. He felt that the reaction vessel needed to be treated. As a result, when the cork was opened, it exploded with force.
The last word of advice, unclear experiments, experiments that don't understand the properties of compounds, be careful when you are in a bad mental state.
(2) The purity of ligands is very important for chemists who do asymmetric catalysis and use ligands to improve the catalytic reactions of some metals. However, due to the different raw materials or the different properties and purity of silica gel and other materials used in purification, the results of the reaction can not be repeated. If the purity of ligands is different before and after screening, or different solvents are used, the reaction conditions before and after screening are not carried out on the premise of comparability, which may lead to some good results being buried.
When we publish the paper, we write down the operation of the test and the purification method of the reagent in detail, just to ensure that others can do the same and repeat the test results. Therefore, we must ensure that our experimental methods are carried out under the same conditions.
During the experiment, we did find that some experimental data were difficult to repeat, which was encountered by many groups engaged in asymmetric research. The reasons may be as follows: 1, the purity of the ligand does not meet the requirements, so the activity and enantioselectivity of the reaction are inconsistent with the previous results, especially the quality of the solvent and silica gel used for separation and purification can not be guaranteed, which leads to the inability to obtain the ligand with the purity meeting the requirements of the research work according to the previous purification conditions; 2. There are errors in the reaction operation: this is particularly prominent in the weighing process. Because the amount of ligand and metal salt is only a few milligrams, the interference of static electricity is particularly prominent in dry weather; 3. The solvents used in the reaction are mostly acetone, and the water content is difficult to detect, such as CH3CN, haloalkane, etc. Different batches of solvents may have different water contents, which leads to unrepeatable reaction results.
In order to ensure the repeatability of experimental data, we explored and established a set of methods and standard reaction conditions for ligand purity inspection. Especially after ligand 30a showed excellent properties in several reactions, this requirement is especially critical for other studies.
After long-term practice, we have summarized the following experiences for reference:
First, the establishment of standard reaction conditions
The CH3CN, triethylamine and carbon tetrachloride used in the synthesis of 1. ligands are treated according to standard methods. After a small amount of reactions prove qualified (ligands can be synthesized), they are stored in activated molecular sieves for later use.
2. If the solvent used in the conditional experiment cannot be guaranteed to be anhydrous by the indicator, it should be treated in strict accordance with the standard method, further treated by activated molecular sieve, and then evaporated for use; For the best solvent that has been screened out, after each new treatment, it is tested by standard reaction, and the ee value can only be used after it meets the previous experiment.
3. During weighing, avoid electrostatic interference as much as possible.
B, the establishment of ligand purity testing method
1, which is used to synthesize new ligands. After the initial purity is determined, it is first used for some anti-? Obtain data about reaction rate and ee value; Then, after purifying the ligand again with different developing agents and taking the purest part, the same reaction as before was repeated under the same conditions. If the reaction situation (including rate and ee value) does not change much, it means that the purity of the ligand has been qualified; If the reaction results are obviously improved, it means that the purity of the ligand has been improved, which requires the ligand to be purified again until the difference of the reaction results is within the error range, which means that the purity of the ligand has been qualified. Example: For ligand 30a, petroleum ether and acetone (4∶ 1, v/v) were used as developing agents, and a yellow oily liquid was obtained by column chromatography. Although the liquid was identified by nuclear magnetic resonance, the purity was very good, but the most commonly used model reaction-DA reaction (EQ1)-was used to test the ligand and Cu was used to test it. After further purification with petroleum ether and ethyl acetate (1: 1, v/v), the reaction was completed within 1 hour, and the ee value was 36%. After the ligand was purified again, the reaction was retried, and the reaction time and ee value of the reaction remained unchanged. Therefore, it is considered that the ligand is very pure and can be used for screening reaction conditions. Every time the ligand is synthesized, it reacts under this reaction condition. When the reaction time and ee value are consistent with the above results, it shows that the ligand purity is qualified before it can be used in conditional reaction.
(3) First of all, from now on, if you have time, soak in the lab and observe how the brothers operate, and don't let go of every detail. Come to think of it, why do you want to do this? If you don't understand, just ask until you figure out why you did it. You can also think clearly about the reasons, and then communicate with other senior brothers to see what others think. Of course, when you first enter the lab, be sure to run more errands, so that you can befriend your brothers and they will be willing to communicate with you more.
Secondly, after entering the laboratory, there are frequent failures, but you must find out the cause of the failure. Don't blindly carry out the same experimental operation without knowing the reason. Remember, do an experiment after analyzing the reasons, and do an experiment once, and you must rule out a possible factor. Don't start a lot of experiments just because you are afraid that your tutor will say that you are not responding enough. The result is that you are trapped in a lot of physical labor and have no time to think, summarize and improve.
Before doing every experiment, don't look up a document, just try it according to the document method. Investigate the literature repeatedly, see what methods can get the target product, what are the advantages and disadvantages of each method, and choose the most convenient start after repeated comparison. This is not only a shortcut to improve work efficiency, but also can cultivate your judgment and accumulate your experience and knowledge. Do you think that you can accumulate a series of data in one experiment, and how much will you gain in one semester? This method is very tiring, but it is absolutely effective. I believe that as long as you persist, you will be completely transformed when you graduate.
For every detail of the literature and experimental steps of your method, you should ask to do this? If you don't do this, what will happen? Can you use other methods instead? Refer to other literature for the synthesis of the same product, and see what other people's experimental steps are? What changes have they made? Why do you want to change it like this? Because experiments are interlinked, once you master these problems and persist for one month, other problems will be solved.
There are many people around me who want to graduate with a doctorate. These problems have not been solved, and I have not seen them clearly.
I didn't expect that the anhydrous treatment method of DMF caused such a big controversy. Undeniably, different experiments have different requirements on the purity of reagents and solvents. There is no need for strict anhydrous reaction, and it is a waste of time for you to carry out strict anhydrous treatment; Or vice versa, I also admit that sometimes the existence of some trace impurities in the reagent often leads to unexpected results in the reaction. As far as I know, there are two such examples: Dr. Li (Dai Lixin Group) used an untreated domestic analytically pure CH3CN solvent in the first step of the reaction of aziridine with high stereoselectivity via the Yelide route. After this article was published in Angel. Chemistry. Ed inside, this caught the attention of a French scientist. However, in the process of repeated experiments, he found that the reaction results could not be repeated by directly using commercial analytical pure CH3CN solvent, and only a certain amount of water could be added to the reaction system, so he wrote an article to correct it. We analyze the reasons and think that the water content of domestic reagents is higher than that of imported reagents; The second example is: Dr. Yuan Yu found that the test results are not repeatable, and the purer the benzaldehyde used, the worse the reaction results. Therefore, it is considered that the initial benzaldehyde may be partially oxidized to benzoic acid, and it is found that using acid as an additive can greatly improve the reaction results (the article is published in Chem. Euro. j)。
However, this does not mean that our experiments do not need to strictly follow the standard methods. Especially when we explore the unknown, we need to sum up the reasons for success (or failure). If the reagent or solvent used in our reaction contains a small amount of impurities, how to ensure the repeatability of the test? How to analyze the experimental results, design the next experimental scheme and improve the experimental effect?
It is more important for freshmen to operate according to a set of standard experimental methods. Because failure is common for beginners, if you can't guarantee the purity of your test reagent and whether it meets the requirement of anhydrous, how can you find the reason once the experiment fails? Is it an operational error or other reasons?
As a graduating student, during several years of experimental career, I deeply felt the importance of testing according to standard methods.
It may be because the asymmetric catalysis I am engaged in is highly sensitive to impurities, so I have spent a lot of time repeating it in recent years to find out the reason.
I am glad that when I first entered the laboratory, I accepted the advice of a senior, that is, all solvents and reagents should be handled in strict accordance with standard methods, even if it is cumbersome. This method is the fourth edition of the book Purification of Laboratory Chemicals edited by W.L.F. Armarego and D.D. Perrin, and it is also strictly implemented by the tutors of various research groups in Shanghai Institute of Organic Machinery. Because this book is constantly synthesizing the latest processing methods in the literature and the latest findings on the shortcomings of various methods, it has been revised.
Six months after my first article was published (j.am. Chemistry. Soc), a Korean chemist, visited our institute and specifically mentioned that it took them half a year to synthesize a ligand exactly like me, but he was very disappointed to find that all our articles were published. Why should I thank the teacher elder sister? After I listened to her advice, all kinds of solvents were strictly treated, so it took me only two weeks to synthesize the ligand. In fact, after the publication of my article, there are still domestic colleagues who can't synthesize ligands repeatedly, and other students in our research group can't synthesize ligands repeatedly at first, because of their solvent treatment.
Some students mentioned that their handling method referred to some documents. In fact, the processing methods of many documents are imperfect and constantly changing. So there will be a special series to summarize. I think people who have been in the laboratory for a long time will find it difficult to repeat the results of some documents. If you carefully study their experimental methods, you will find that some operations are completely unnecessary and some are wrong. Of course, the author may have reservations.
One of the ways to improve our chemistry literacy is to judge the correctness of the literature according to our own knowledge, rather than blindly following it.
Tell me a question about vacuum distillation.
When I distilled a substituted phenylacetonitrile product under reduced pressure, some NaBr in the crude product could not be completely removed, probably because of the sublimation of NaBr during distillation, which led to a sharp decline in vacuum after a period of time. I didn't notice the problem at that time. So I have nearly 1kg of products, so KO! Tragedy!
Therefore, please be more careful when carrying out vacuum distillation. The most important thing is: don't leave during vacuum distillation ~! We should always pay attention to the change of pressure in order to take positive measures!
Doing experiments is always troublesome, and I don't like wearing rubber gloves. Because concentrated nitric acid and hydrogen peroxide are often used, it hurts the skin, and the skin is either white or yellow. Especially the recent report about shaped calcium hydrogen peroxide, I'm really afraid that it was also hydrogen peroxide that day ... I hope XDJM won't disturb you and must take care of yourself.
Also, we should pay attention to similar problems when using potassium permanganate. In the dermatology department of the hospital, potassium permanganate is often prescribed as an external washing drug, and the medical name is pp powder. So a PPMM asked her boyfriend to go to the chemistry department to take some back to wash ... and it turned yellow and hurt, mainly because she mixed too much concentration. Take a warning! ! !
Use aluminum-nickel alloy to drop concentrated alkali for hydrogenation reduction, and pay attention to the dropping speed must be slow! Because the reaction is strongly exothermic, it may lead to boiling or even explosion accidents!
In addition, in the experiment, the substance added in the reaction flask should not exceed 2/3 of the solvent in the flask. Once I added too much, the volume of the material increased a little after heating during the reaction, and all of it overflowed, so my oil bath pot was scrapped. .....
In order to remove the residual sodium after the reaction, sodium must be treated with anhydrous ethanol to avoid explosion.
Another experimental lesson is that DMF should not be dehydrated and dried with Na. Once, a colleague in our laboratory did this operation on a 5-liter flask and got a pot of porridge. Estimates that two people have to react!
Drying polyethylene glycol with magnesium sulfate results in a pot of porridge! ! !
The catalyst used for catalytic hydrogenation must be fire-proof! ! !
I don't know if there was any mistake when installing the rubber cover on the mixing sleeve. I saw with my own eyes that a colleague was punctured by the handle of the glass sleeve because of excessive force. The most cruel thing is that a colleague actually punctured the tendon of his wrist when connecting the rubber sleeve to the condenser tube. This is by no means alarmist. This is a bloody reality!
I don't know if you often use autoclave to react. Personally, I think this guy has a large risk factor, so we should always pay attention to the change of pressure. I have done ammonolysis experiment for a long time, and it has always been good, so I let my guard down. As a result, once the pressure suddenly became 120kg, but fortunately it didn't explode, otherwise I would be finished.
I don't feel any danger from high pressure. The autoclave in our unit is 120kg, 500l, no problem. When there is a mutation, anything is possible. I have been engaged in the chemical industry for 8 years and have witnessed no less than 8 fires and explosions.
When my colleague filtered with a glass syringe filter, the glass syringe broke, cut his palm and almost shortened his nerve.
When drying the dropping funnel and the separating funnel, it is best to take out the piston and dry it, otherwise the piston will burst the funnel due to different expansion coefficients.
I baked several constant-pressure funnels, and as a result, I wasted a lot of money on my boss. A 1000ml constant pressure funnel costs 40 yuan, and my heart is broken.
Chemistry is particularly dangerous. A brother upstairs in our laboratory made azide the other day. It was summer, and he kept cooking at room temperature. There is nothing wrong, but I don't know what happened that day. I just shook it and the blood came out. Fortunately, he wore goggles and the mirror was broken, but fortunately, it didn't hurt my eyes.
Therefore, everyone must not be lucky when doing experiments, and must kill one thousand by mistake and not let go of one. Hehe, be careful.
What I can't understand most is that many graduate students can throw untreated sodium into the trash can. My teacher has caught fire on the laboratory furniture of the group opposite me twice, and the teacher who just caught fire in our group saw it and helped them put it out (there was no one in their laboratory). This kind of low-level mistake may be made by few people.
If you want to use the acidity meter in the experiment, you must observe the working conditions of the acidity meter, such as temperature/humidity.
I remember that I suffered a loss in the experiment and the analysis result was wrong. I searched all the way from the buffer-reagent, and finally found that it was just cold.
Be sure to keep in mind the concept of temperature and accurately record the temperature of each reaction step, which is not the general room temperature or even the post-treatment temperature. Many technologies can't be repeated after they arrive at the factory, which may be due to the temperature.
I have a project that I did well in summer and suddenly failed in winter. Later, I changed the reaction conditions and recrystallization conditions to get it. Pretty scary. There is something wrong with the 654.38+00,000 project, so I have to finish class.
High pressure reactor must be equipped with explosion-proof plate;
Flammable and explosive gas, leakage test must be strict (use' electronic pen');
Don't repair electrical equipment yourself (someone in our unit almost died);
The toxic experimental environment must be well ventilated and wear anti-virus appliances;
The laboratory should have good experimental habits, strict operating procedures and responsibility system.
Don't forget to open the condensed water during distillation or rectification, but some serious and unremarkable mistakes may lead to irreparable losses!
I have seen someone pour the residue into the sink after doing the experiment of the reaction between anhydrous ethanol and sodium metal. As a result, the metal sodium that did not react completely just touched the residual acid in the sink and exploded. A fireball flew out. Fortunately, no one was hurt! ! !
Before drying the test tube with CaCl2 _ 2, be sure to check whether the drying test tube is open.
Because I didn't check it, I refluxed it several times. After the temperature rises, the drying pipe is pushed upward by the rising hot air and burst.
When one of my younger brothers contributed to silver perchlorate, there was a little residue in the bottle mouth, and the bottle stopper burst as soon as it was ground. Fortunately, a few grams of things in the bottle didn't explode, otherwise he would fly.
Everyone must be careful when using aluminum trichloride, aluminum trichloride will react strongly and even explode when it meets water!
When making NaH, the bottle broke and there was water on the table, which exploded at once. It is really dangerous.
When using oxidants such as hydrogen peroxide and m-chloroperoxybenzoic acid, the post-treatment must be thoroughly treated with reducing agent, and then it is very easy to explode.
When doing the experiment, I accidentally touched phenol and burned a layer of skin. What a good lesson! Was washed with dilute NaOH. Another time I forgot to turn off the water and came out the next day.
Speaking of which, I'm ashamed. I also experienced an experiment that almost had an accident. I once borrowed someone else's alcohol burner. Because of the long time, the interface between the plastic pipe (which should be a rubber pipe) and the blowtorch caught fire. Fortunately, there was not much alcohol, so I pinched one end of the pipe (to prevent alcohol from flowing out) and put out the fire with a big wet rag. Although the accident was eliminated in time, I was still scared out in a cold sweat.
Do not operate under pressure when doing high pressure reaction experiments! When moving valves and screws, be sure to check whether the vent pipe is open or it may fly, which is very dangerous!
Everyone must be careful when doing experiments. Once I did vacuum distillation and failed to repair the condensation system. As a result, the solvent was sprayed out of the bottle mouth and the product was sprayed out!
Do not pour LaNi5 powder which has been tested by hydrogen storage directly into the trash can, because the particles are extremely fine and easy to oxidize and burn. I have seen it several times in our laboratory, but fortunately someone was there, otherwise the consequences would be unimaginable. Better wrap it in wet paper.
When you need to control the PH value, you must use an acid meter instead of a test paper. I did an experiment, and the difference was 3-4. Haha, the result can be imagined.
The format reaction requires anhydrous tetrahydrofuran, and sodium metal is used to remove water. After steaming out, I left the flask for a few days. I mistakenly thought that sodium had completely reacted, so I added water directly without adding alcohol. At first, there was nothing unusual. After a while, it started to smoke ... and then it exploded! Fortunately, this is only a minor injury. I have a lingering fear!
Sodium peroxide reacts with water, and sparks are detected by wood strips. Because my personal chemistry experiment accomplishment is not very good. They are all greedy! I took three teaspoons of sodium peroxide, but only added a few drops of water. I tested it with a piece of wood with Mars, and it was successful. Later, out of curiosity about the new heart, I put a piece of wood with Mars in the bottom of the test tube, and the result-explosion! Fortunately, when I took the test tube, I took a big hard test tube. Or you will die! The reason is that there is a lot of sodium peroxide and a little oxygen at the bottom of the test tube. Stretching the wood strip with Mars to the bottom of the test tube first produces carbon dioxide, which reacts with sodium peroxide to produce oxygen, and the wood strip with Mars reacts with oxygen to produce carbon dioxide ... thus producing a large amount of gas and exploding at one time.
So when we do the experiment, we must do it in strict accordance with the dose.
It was originally a very simple middle school experiment, but it almost killed a college student because of the dose problem!
Be sure to deal with the new sand core funnel before use, or wait and hear!
Let me talk about using pickling reaction solution. If it is neutralized with NaHCO3, it should be washed with water first, otherwise a large amount of gas will be produced during liquid separation.
Be careful when handling desiccant. Never judge by appearances. Be sure to find out what it is. Once when I was treating it, I saw that it was invalid calcium oxide. There was sodium in it, boy. I almost died. Be careful, be careful, especially those left by others.
Acrylic acid is also dangerous. Last time, a senior filled half a bottle with a grinding mouth and put it in a place with strong sunshine. It exploded and almost disfigured.
Remember not to leave people when the temperature rises slowly. I don't know how many experiments have been ruined! It is easy to get stuck in the hot water cock of the separatory funnel. Last month, I crushed one, so I had to put several band-AIDS on my hand and struggled for another three days!
I also want to say a few words. In organic synthesis, it is sometimes impossible to do it in the final quaternization stage, because the acid-base neutralization quickly releases heat to produce foam, and then defoaming agent is added in the middle and early stage, and the effect is good.
When pressurizing the chromatographic column, pay attention to prevent the eluent from rushing out due to excessive pressure. Especially when the eluent is added.
Hydrogenation reduction means that palladium carbon or raney nickel must be careful not to put it in the air. When I was doing synephrine synthesis, some palladium carbon was exposed to the air under the protection of ethanol, causing combustion and explosion. Fortunately, the rescue was timely, otherwise there would be more than one ton of ethanol in the next kettle, and the consequences would be unimaginable. You must be careful.
After vacuum distillation, it is best to cool and vacuum.
A factory exploded because it didn't cool down, and I caught fire once.
Also pay attention to the nitrification of food samples. Generally, the mixed acid method of sulfuric acid, nitric acid and perchloric acid is used for digestion, so the digestion must not be fast, otherwise an explosion will occur when processing a large number of starch samples.
The Friedel-Crafts reaction was carried out with anhydrous aluminum trichloride as catalyst, and the released hydrogen chloride was absorbed by circulating water. Once, after the reaction was completed, the temperature was cooled down from 80 degrees to 40 degrees. Because it was not emptied in time, the water returned to the substance, and the substance rushed to the ceiling, which was so scary! I'm scared to think of it. You should pay attention to negative pressure.
Recently, I was doing a synthetic experiment for two weeks, according to the literature, but the literature only used four words (ethanol precipitation) to explain the post-treatment of the product. In order to remove products from PH and NaCl above ph 14, I had to do the last experiment first. At first, I thought ethanol was enough, so I tried my best to add ethanol. I was exhausted and wasted 5-6 bottles of anhydrous ethanol. Of course, later, NACL could not be used. Later, I thought about it. Isn't it precipitated with ethanol? Precipitation means settling down. What should I use for analysis? Absolute ethanol, of course. In what solution should I dissolve and precipitate? So I thought, I have to keep adding water, and then ethanol, so as to get the final result. Soluble β -cyclodextrin product has strong solubility in water, and it will precipitate out in ethanol and become sticky immediately, but when I add some ethanol and stir for a while, it will not be sticky, and when I stir again, there will be particles without viscosity at all.