The nature of the reagent
1. Sodium amide The purity of the commercially available granulated sodium amide is 80 to 90%. The sodium amide is not easily ground, and is usually ground in a mortar containing a hydrocarbon inert solvent such as toluene, xylene or the like. Exposure of sodium amide to air at room temperature for 2 to 3 days can create a dangerous mixture. For safety, the open sodium amide should be used immediately and the container should not be placed for more than 12 hours. When sodium amide forms an oxide (the color turns yellow or brown) it is very explosive and can no longer be used. A small amount of unused sodium amide was added to toluene to completely cover it, and ethanol diluted with toluene was slowly added under stirring to decompose it.
The laboratory prepared sodium amide from sodium and liquid ammonia under the catalysis of ferric ions: 300 mL of anhydrous liquid ammonia was added to a 500 mL three-necked flask. The three-necked flask is provided with a glass stopper, a sealed stirring rod, and a reflux condenser equipped with a soda lime drying tube. With stirring, 0.5 g of sodium was added to the solution, and the solution was blue. Then 0.5 g of ferric nitrate powder catalyst was added and 13.3 g of cut sodium was added over 30 minutes. When sodium is converted to sodium amide, the solution is changed from blue to gray suspension, and a sufficient amount of anhydrous diethyl ether is added from the dropping funnel to keep the liquid volume at about 300 mL. The ammonia was distilled off at elevated temperature. After almost all of the ammonia was distilled off, the sodium amide suspension was stirred, heated to reflux for 5 min, and then cooled to room temperature to obtain an ether suspension of 23.4 g of sodium amide, which was almost quantitative.
The laboratory prepared sodium amide from sodium and liquid ammonia under the catalysis of ferric ions: 300 mL of anhydrous liquid ammonia was added to a 500 mL three-necked flask. The three-necked flask is provided with a glass stopper, a sealed stirring rod, and a reflux condenser equipped with a soda lime drying tube. With stirring, 0.5 g of sodium was added to the solution, and the solution was blue. Then 0.5 g of ferric nitrate powder catalyst was added and 13.3 g of cut sodium was added over 30 minutes. When sodium is converted to sodium amide, the solution is changed from blue to gray suspension, and a sufficient amount of anhydrous diethyl ether is added from the dropping funnel to keep the liquid volume at about 300 mL. The ammonia was distilled off at elevated temperature. After almost all of the ammonia was distilled off, the sodium amide suspension was stirred, heated to reflux for 5 min, and then cooled to room temperature to obtain an ether suspension of 23.4 g of sodium amide, which was almost quantitative.
2. Ammonia Gas ammonia is generally contained in a cylinder, and gaseous ammonia can be obtained by a pressure reducing device during use. The flow rate of the gas can be controlled by a bubble meter containing a small amount of concentrated potassium hydroxide solution (12 g of potassium hydroxide dissolved in 12 mL of water). A safety bottle should be added between the meter and the reactor. Drying through a drying tower containing loose soda lime or bulk calcium oxide.
If a small amount of ammonia is required, it can be prepared by adding concentrated ammonia water to a round bottom flask equipped with a reflux condenser at the upper end, slowly heating, and drying the gas through a drying tower equipped with loose soda lime or massive calcium oxide, and then passed through A safety bottle is introduced into the reaction flask.
3. The boiling point of benzene is 80.1 ° C, the density is d = 0.8791, it is insoluble in water and can be miscible with ethanol. The melting point is 5.2 ° C. Industrial benzene often contains thiophene, and the boiling point of thiophene (84 ° C) is close to that of benzene and cannot be separated by distillation. Check the presence or absence of thiophene in benzene. Add 5 mL of benzene to a solution of 10 mL of blush and 10 mL of concentrated sulfuric acid. Shake for a while. When thiophene is present, the acid layer will be light blue.
To prepare anhydrous thiophene-free benzene, it is generally possible to wash with concentrated sulfuric acid at room temperature. Take a concentrated sulfuric acid washing with a volume equivalent to 15% by volume of benzene, repeat the operation until the acid layer is colorless or light yellow, then wash with water until neutral, dry with anhydrous calcium chloride, distill, collect 79-81 ° C The fraction is finally dehydrated to anhydrous benzene with sodium metal.
4. The pyridine has a boiling point of 115.5 ° C, a density d = 1.5095, and a refractive index n 20D = 0.9819. The pure pyridine is analyzed to contain a small amount of water. If an anhydrous pyridine is to be prepared, the pyridine and the granular potassium hydroxide may be refluxed together, and then the moisture is distilled off to be used. The dried pyridine is very absorbent and should be sealed with paraffin when stored.
5. Palladium Catalysts Palladium catalysts are very effective hydrogenation catalysts and are relatively expensive. The laboratory can prepare palladium catalyst from palladium chloride.
(1) Preparation of Pd-C (5% Pd): 1.7 g of palladium chloride and 1.7 mL of concentrated hydrochloric acid were added to 20 mL of water, heated in a water bath for 2 hours to dissolve completely, and then it was added to dissolve 30 g in 200 mL of water. In a solution of sodium acetate, it was placed in a 500 mL flask. 20 g of acid washed activated carbon was added and hydrogenated in a hydrogen atmosphere until the end of the reaction. The catalyst was collected by filtration, washed with 5 portions of 100 mL of water and suction filtered. Dry with potassium hydroxide at room temperature or dry with anhydrous calcium chloride in a vacuum desiccator. The catalyst was ground to a powder and stored in a reagent bottle that was stoppered.
(2) Preparation of Pd-C (30% Pd): 8.25 g of palladium chloride and 5 mL of concentrated hydrochloric acid were added to 50 mL of water. Under ice cooling, 50 mL of 40% acetaldehyde solution was added, followed by 11 g of acid washed activated carbon. A solution of 50 g of potassium hydroxide dissolved in 50 mL of water was added under mechanical stirring to maintain the temperature below 50 °C. After the addition, the temperature was raised to 60 ° C for 15 min, and the catalyst was thoroughly washed with water, and then the water was poured out; washed with acetic acid, suction filtered, and washed with water until no Cl- and OH- ions. Dry at 100 ° C and store in a desiccator.
(3) Preparation of palladium black: 5 g of palladium chloride was dissolved in 30 mL of concentrated hydrochloric acid, diluted with 80 mL of water, and 35 mL of 40% acetaldehyde solution was added under cooling with an ice salt bath. Dissolve 35 g of potassium hydroxide in 35 mL of water and add it to the mixture over 30 min with vigorous stirring. After heating to 60 ° C, after 30 min, the water was decanted and the precipitate was washed 6 times with water, filtered onto a crucible, washed with 1 L of water, blotted dry, and dried in a desiccator to yield 3.1 g.
(4) Preparation of Pd-BaSO4 (5% Pd): Add a hot solution of 63.1 g of cesium hydroxide dissolved in 600 mL of water (t=80 °C) in a 2 L beaker, and add 60 mL of 3 mol at a time with rapid stirring. ? L-1 sulfuric acid. Add 3 mol? L-1 sulfuric acid to make the suspension acidic to litmus. Dissolve 4.1 g of palladium chloride in 10 mL of concentrated hydrochloric acid, dilute with 20 mL of water, add barium sulfate solution under mechanical stirring, and then add 4 mL of 40% acetaldehyde solution. Adjust to a weak alkaline with 30% sodium hydroxide solution, continue stirring for 5 min, and let stand. Pour out the upper layer of the night, wash with water, and then let stand, repeat 8 to 10 times. Filter, wash with 5 parts of 25 mL of water, blot as much as possible, dry at 80 ° C, grind fine catalyst, seal in bottle and set aside.
6. acetone
The boiling point of 56 ° C, density d = 0.7898, can be miscible with water, ethanol, ether. Industrial acetone contains impurities such as methanol, ethanol, acid, and water. In general, the acetone is purified by refluxing acetone and potassium permanganate until the purple color of the added potassium permanganate is no longer removed, and then the acetone is distilled off, dried with anhydrous potassium carbonate, and then distilled.
7. glacial acetic acid
The boiling point of 117 ° C, the commercially available acetic acid slowly crystallized at 4 ° C, filtered, and dried. A small amount of water can be removed by refluxing with phosphorus pentoxide for several hours. Glacial acetic acid has a corrosive effect on the skin. When it touches the skin or splashes on the eyes, it should be washed with plenty of water.
8. Nitrogen and nitrogen are generally stored in a cylinder in the form of compressed gas, generally containing traces of oxygen, which can be removed by the following methods: (1) by an alkali solution of gallic acid (15 g of gallic acid dissolved in 100 mL of 50% NaOH solution); (2) Preparation method of the solution by Fieser solution: 20 g of potassium hydroxide is dissolved in 100 mL of water, and 2 g of sodium sulfonate-2-sulfonate and 15 g of sodium hydrogen sulfite are slightly stirred to dissolve, when the blood is dissolved. The red solution can be used to cool to room temperature. The solution can absorb 750 mL of oxygen. When the color of the solution changes to brown or a precipitate forms, the solution loses its effect. There are also commercially available high purity nitrogen free of oxygen, but the price is more expensive.
9 . N,N-dimethylformamide (DMF)
The boiling point is 149 ~ 156 ° C, the density d = 0.9487, the refractive index n 20D = 1. 4305, colorless liquid, can be miscible with most organic solvents and water, is an excellent organic solvent. Commercially available DMF contains small amounts of impurities such as water, amines and formaldehyde. Some decomposition occurs during atmospheric distillation to produce dimethylamine and carbon monoxide. If acid or alkali is present, the decomposition is accelerated. After adding solid potassium hydroxide or sodium hydroxide, it is partially decomposed after being left at room temperature for several hours. Therefore, it is preferably dried with calcium sulfate, magnesium sulfate, cerium oxide, silica gel or molecular sieve, and then distilled under reduced pressure to collect a fraction of 76 ° C / 4.79 kPa (36 mmHg). If the water content is high, one tenth of the volume of benzene may be added, and water and benzene are distilled off under normal pressure and below 80 ° C, and then dried with magnesium sulfate or cerium oxide, and then distilled under reduced pressure.
10 . Dimethyl sulfoxide <br>Boiling point 189 ° C, melting point 18.5 ° C, density d = 1.100, refractive index n 20D = 1.4783. Dimethyl sulfoxide is miscible with water and can be dried by long-term placement with molecular sieves. Then, it was distilled under reduced pressure, and a fraction of 76 ° C / 1.6 kPa was collected. The temperature during distillation should not exceed 90 ° C, otherwise disproportionation will occur to form dimethyl sulfone and dimethyl sulfide. It may also be dried by using calcium oxide, cerium oxide or anhydrous barium sulfate, and then distilled under reduced pressure. When dimethyl sulfoxide is mixed with certain substances, it may explode, such as sodium hydride, periodic acid or magnesium perchlorate.
11 . Carbon dioxide Carbon dioxide can be produced in a chirp generator using calcium carbonate and dilute hydrochloric acid (1:1). The acid mist is removed by passing the gas through a gas cylinder containing sodium bicarbonate. If drying is required, the gas is passed to another two scrubbers containing concentrated sulfuric acid.
A large amount of carbon dioxide can be used in commercial cylinder gas, and the gas can be dried by two gas cylinders filled with concentrated sulfuric acid, and a small amount of air is present in the carbon dioxide gas.
In order to achieve certain experimental purposes (such as Grignard reaction), solid carbon dioxide (dry ice) can be used. Note that solid carbon dioxide cannot be taken directly by hand without protection, otherwise it will be frostbitten. If you want to use dry ice powder, wrap large chunks of dry ice in a cloth and mash. The carbon dioxide gas can be stably supplied when the dry ice is volatilized, and the appropriate size of dry ice can be placed in the flask, and the generated gas is connected to the reactor through a concentrated sulfuric acid gas cylinder and a safety bottle.
12 . The main use of manganese dioxide in manganese dioxide is to selectively oxidize 1o and 2o alcohols containing allyl and benzyl groups to the corresponding carbonyl compounds. The activity of manganese dioxide varies with the preparation method. Highly active manganese dioxide can be obtained by oxidizing divalent manganese ions with an excess of permanganate under basic conditions:
Dissolve 223 g (1 mol) of manganese sulfate tetrahydrate in 300 mL of water to form solution (a), prepare 240 mL of 40% aqueous solution of sodium hydroxide (b), and then dissolve 190 g (1.2 mol) in 1200 mL of water. Potassium permanganate was stirred with heating, and (a) and (b) were simultaneously added thereto over 1 hour, and finally a pure manganese dioxide brown precipitate was separated. The manganese dioxide is very fine, centrifuged, and thoroughly washed with water until the solution is colorless, and dried at 100 to 120 °C. It is also possible to extend the filtration time as much as possible to remove most of the water, and then distill the remaining water with 150 mL of benzene and 25 g of filter cake. The manganese dioxide reactivity obtained by the precipitation method is sufficient for the direct oxidation reaction. To evaluate the reactivity of a manganese dioxide sample, dissolve 0.25 g of pure phenylpropanol in 50 mL of dry petroleum ether (bp 30-60 ° C), and add 2 g of MnO2 sample previously dried with P2O5. The solution was shaken at room temperature for 2 hours. Filtration, evaporation of the solvent, the product was treated with sulfonic acid salt of 2,4-dinitrophenylhydrazine in methanol. The obtained cinnamaldehyde 2,4-dinitrophenylhydrazine was collected and recrystallized from ethyl acetate. The yield of the highly active manganese dioxide-derived derivative should exceed 0.35 g (60%) and the melting point was 255 °C.
13 . Dioxane <br> Boiling point 104.5 ° C, density d = 1.0336. It is miscible with water, colorless, flammable, and can form an azeotrope with water (content is 81.6%, boiling point 87.8 ° C). It usually contains a small amount of diacetal acetal and water. It can be refluxed with 10% concentrated hydrochloric acid for 3 hours. Nitrogen gas was slowly introduced to remove the generated acetaldehyde. After cooling, the granular potassium hydroxide was added until it was no longer dissolved, the aqueous layer was separated, and dried with granular potassium hydroxide for one day. Filtration, addition of sodium metal reflux for several hours, distillation. The long-lasting dioxane may contain peroxide, which should be removed and then treated.
14 . N,N-dicyclohexylcarbodiimide (DCC; C6H11N=C=NC6H11)
The melting point of 33 ~ 35 ° C, is a waxy low melting point solid, the agent is very corrosive to the skin, it can cause allergies, must be careful when using. High quality DCC (purity 99%) can be purchased, and the reagent bottle can be liquefied in a small amount of hot water for weighing.
This reagent is often used as a dehydrating agent and is removed as a dicyclohexylurea after the reaction. The recovered dicyclohexylurea (mp 234 ° C) can be recrystallized from ethanol and then converted to DCC by reaction with p-toluenesulfonyl chloride, phosphorus oxychloride or phosphorus pentoxide in a pyridine solution: 17.1 g (47 mL) with stirring. , 0.11 mol) of phosphorus oxychloride was added dropwise to a solution of 22.5 g (0.1 mol) of dicyclohexylurea in 50 mL of pyridine, and then heated to 60-90 ° C for 1.5 hours, and the reaction product was poured on crushed ice. The mixture was extracted with petroleum ether (bp 60-80 ° C), dried over anhydrous sodium sulfate, and then evaporated. The yield of the diimide is about 14 g (68%), bp 157 to 159 ° C / 2.0 kPa (131 ° C / 0.5 kPa).
15 . Potassium Fluoride <br>Anhydrous Potassium Fluoride can be prepared by the following steps: potassium fluoride crystals are finely ground, heated to 180-210 ° C with a heating mantle, and stored in a desiccator. Potassium fluoride was dried for three hours before use and then ground in a heated mortar (50 ° C).
16 . Chromium oxidants Cr(VI) is widely used as an oxidant in organic chemistry. Chromium oxide is a deliquescent red crystal that is easily soluble in water and sulfuric acid. It is a strong oxidant and must be handled with care. It is usually used in its acetic acid or acetic anhydride solution. Adding chromium oxide to ice-cold acetic anhydride can be formulated into a solution of chromium oxide in acetic anhydride. It is important not to add an acid anhydride to the chromium oxide. Adding the acid anhydride to a large amount of chromium oxide causes explosive decomposition. In the reaction of oxidizing a simple primary alcohol to an aldehyde, a secondary alcohol to a ketone, and an alkylborane to a ketone, an aqueous solution of sodium dichromate in sulfuric acid may also be used as the oxidizing agent. Since the aldehyde formed by the oxidation of the primary alcohol is continuously oxidized to a carboxylic acid, the acid chromate is generally not used to oxidize the primary alcohol to form an aldehyde. Cr(VI) can be selectively oxidized in an inert medium. Currently, Cr(VI) pyridine complexes (dichromate pyridinium and chlorochromate pyridinium) are widely used in primary alcohols and acid-sensitive group alcohols. Selective oxidation.
The step of oxidizing the primary alcohol and the secondary alcohol with dichromate pyridinium salt is: adding 6 g (60 mmol) of chromium trioxide to 150 mL of pyridine containing 9.49 g (12 mmol) of dichloromethane under magnetic stirring. Then, the flask was stoppered with a drying tube containing a desiccant, the solution was dark purple, stirred for 15 min, and a part of an alcohol solution (10 mmol) dissolved in a small amount of dichloromethane was added at the end of stirring, and a black precipitate was observed immediately. When the temperature of the solution was kept at room temperature, stirring was continued for 15 min. At this time, the solution and the residue were separated, and the residue was washed with 200 mL of diethyl ether. The organic layer was washed three times with three 100 mL portions of 5% aqueous NaOH solution, once with 100 mL of 5% aqueous HCl solution, once with 100 mL of 5% aqueous NaHCO3 solution, once with 100 mL of a saturated aqueous solution of NaCl, and then dried over magnesium sulfate. Finally, the layered methylene chloride was concentrated, and the residue was extracted with diethyl ether. The insoluble chromium salt was filtered, washed with dilute alkali and saturated brine, dried over magnesium sulfate, and evaporated to give a crude product of aldehyde and ketone. . The alcohol which can be oxidized by such a procedure is 2-octanol (97% yield of carbonyl compound), 1-octanol (90%), benzyl alcohol (89%), borneol (89%), cinnamyl alcohol (96). %).
Pyridinium chlorochromate is formed by the action of chromium trioxide and pyridine in the presence of hydrochloric acid. It has a weak acidity and easily reacts with a basic group, and it can replace the oxidic acid dichromate pyridinium salt. The pyridinium chlorochromate can be prepared by the following method: 100 g (1 mol) of chromium oxide (VI) is rapidly added to 184 mL of 6 mol?L-1 HCl (1.1 mol) during stirring, and the solution is cooled after 5 min. To 0 ° C, carefully add 79.1 g (1 mol) of pyridine (at least 10 min), re-cooled to 0 ° C, to give an orange-yellow solid, the solid was placed in a fritted glass funnel, and dried in vacuo for 1 hour to give the product 188.8 g (84%). It is not easy to measure whether the solid is completely dry with a moisture analyzer, so it needs to be left at room temperature for a while. The pyridinium chlorochromate can oxidize 1-heptanol to heptaldehyde.
The pyridinium chlorochromate adsorbed on alumina in some reactions is more effective. At 40 ° C, 6 g of chromium trioxide dissolved in 11 mL of hydrochloric acid (6 mol? L-1), 4.75 g of pyridine was added within 10 min, the solution was cooled to below 10 ° C until an orange-yellow solid formed, and then heated to 40 At ° C, the solid was dissolved, 50 g of alumina was added under stirring, the temperature was kept at 40 ° C, and the solvent was evaporated to give an orange solid, which was dried in vacuo for 2 hr. The reagent can be stored in a vacuum desiccator for several weeks in the dark, and its activity is unchanged.
If a small amount of ammonia is required, it can be prepared by adding concentrated ammonia water to a round bottom flask equipped with a reflux condenser at the upper end, slowly heating, and drying the gas through a drying tower equipped with loose soda lime or massive calcium oxide, and then passed through A safety bottle is introduced into the reaction flask.
3. The boiling point of benzene is 80.1 ° C, the density is d = 0.8791, it is insoluble in water and can be miscible with ethanol. The melting point is 5.2 ° C. Industrial benzene often contains thiophene, and the boiling point of thiophene (84 ° C) is close to that of benzene and cannot be separated by distillation. Check the presence or absence of thiophene in benzene. Add 5 mL of benzene to a solution of 10 mL of blush and 10 mL of concentrated sulfuric acid. Shake for a while. When thiophene is present, the acid layer will be light blue.
To prepare anhydrous thiophene-free benzene, it is generally possible to wash with concentrated sulfuric acid at room temperature. Take a concentrated sulfuric acid washing with a volume equivalent to 15% by volume of benzene, repeat the operation until the acid layer is colorless or light yellow, then wash with water until neutral, dry with anhydrous calcium chloride, distill, collect 79-81 ° C The fraction is finally dehydrated to anhydrous benzene with sodium metal.
4. The pyridine has a boiling point of 115.5 ° C, a density d = 1.5095, and a refractive index n 20D = 0.9819. The pure pyridine is analyzed to contain a small amount of water. If an anhydrous pyridine is to be prepared, the pyridine and the granular potassium hydroxide may be refluxed together, and then the moisture is distilled off to be used. The dried pyridine is very absorbent and should be sealed with paraffin when stored.
5. Palladium Catalysts Palladium catalysts are very effective hydrogenation catalysts and are relatively expensive. The laboratory can prepare palladium catalyst from palladium chloride.
(1) Preparation of Pd-C (5% Pd): 1.7 g of palladium chloride and 1.7 mL of concentrated hydrochloric acid were added to 20 mL of water, heated in a water bath for 2 hours to dissolve completely, and then it was added to dissolve 30 g in 200 mL of water. In a solution of sodium acetate, it was placed in a 500 mL flask. 20 g of acid washed activated carbon was added and hydrogenated in a hydrogen atmosphere until the end of the reaction. The catalyst was collected by filtration, washed with 5 portions of 100 mL of water and suction filtered. Dry with potassium hydroxide at room temperature or dry with anhydrous calcium chloride in a vacuum desiccator. The catalyst was ground to a powder and stored in a reagent bottle that was stoppered.
(2) Preparation of Pd-C (30% Pd): 8.25 g of palladium chloride and 5 mL of concentrated hydrochloric acid were added to 50 mL of water. Under ice cooling, 50 mL of 40% acetaldehyde solution was added, followed by 11 g of acid washed activated carbon. A solution of 50 g of potassium hydroxide dissolved in 50 mL of water was added under mechanical stirring to maintain the temperature below 50 °C. After the addition, the temperature was raised to 60 ° C for 15 min, and the catalyst was thoroughly washed with water, and then the water was poured out; washed with acetic acid, suction filtered, and washed with water until no Cl- and OH- ions. Dry at 100 ° C and store in a desiccator.
(3) Preparation of palladium black: 5 g of palladium chloride was dissolved in 30 mL of concentrated hydrochloric acid, diluted with 80 mL of water, and 35 mL of 40% acetaldehyde solution was added under cooling with an ice salt bath. Dissolve 35 g of potassium hydroxide in 35 mL of water and add it to the mixture over 30 min with vigorous stirring. After heating to 60 ° C, after 30 min, the water was decanted and the precipitate was washed 6 times with water, filtered onto a crucible, washed with 1 L of water, blotted dry, and dried in a desiccator to yield 3.1 g.
(4) Preparation of Pd-BaSO4 (5% Pd): Add a hot solution of 63.1 g of cesium hydroxide dissolved in 600 mL of water (t=80 °C) in a 2 L beaker, and add 60 mL of 3 mol at a time with rapid stirring. ? L-1 sulfuric acid. Add 3 mol? L-1 sulfuric acid to make the suspension acidic to litmus. Dissolve 4.1 g of palladium chloride in 10 mL of concentrated hydrochloric acid, dilute with 20 mL of water, add barium sulfate solution under mechanical stirring, and then add 4 mL of 40% acetaldehyde solution. Adjust to a weak alkaline with 30% sodium hydroxide solution, continue stirring for 5 min, and let stand. Pour out the upper layer of the night, wash with water, and then let stand, repeat 8 to 10 times. Filter, wash with 5 parts of 25 mL of water, blot as much as possible, dry at 80 ° C, grind fine catalyst, seal in bottle and set aside.
6. acetone
The boiling point of 56 ° C, density d = 0.7898, can be miscible with water, ethanol, ether. Industrial acetone contains impurities such as methanol, ethanol, acid, and water. In general, the acetone is purified by refluxing acetone and potassium permanganate until the purple color of the added potassium permanganate is no longer removed, and then the acetone is distilled off, dried with anhydrous potassium carbonate, and then distilled.
7. glacial acetic acid
The boiling point of 117 ° C, the commercially available acetic acid slowly crystallized at 4 ° C, filtered, and dried. A small amount of water can be removed by refluxing with phosphorus pentoxide for several hours. Glacial acetic acid has a corrosive effect on the skin. When it touches the skin or splashes on the eyes, it should be washed with plenty of water.
8. Nitrogen and nitrogen are generally stored in a cylinder in the form of compressed gas, generally containing traces of oxygen, which can be removed by the following methods: (1) by an alkali solution of gallic acid (15 g of gallic acid dissolved in 100 mL of 50% NaOH solution); (2) Preparation method of the solution by Fieser solution: 20 g of potassium hydroxide is dissolved in 100 mL of water, and 2 g of sodium sulfonate-2-sulfonate and 15 g of sodium hydrogen sulfite are slightly stirred to dissolve, when the blood is dissolved. The red solution can be used to cool to room temperature. The solution can absorb 750 mL of oxygen. When the color of the solution changes to brown or a precipitate forms, the solution loses its effect. There are also commercially available high purity nitrogen free of oxygen, but the price is more expensive.
9 . N,N-dimethylformamide (DMF)
The boiling point is 149 ~ 156 ° C, the density d = 0.9487, the refractive index n 20D = 1. 4305, colorless liquid, can be miscible with most organic solvents and water, is an excellent organic solvent. Commercially available DMF contains small amounts of impurities such as water, amines and formaldehyde. Some decomposition occurs during atmospheric distillation to produce dimethylamine and carbon monoxide. If acid or alkali is present, the decomposition is accelerated. After adding solid potassium hydroxide or sodium hydroxide, it is partially decomposed after being left at room temperature for several hours. Therefore, it is preferably dried with calcium sulfate, magnesium sulfate, cerium oxide, silica gel or molecular sieve, and then distilled under reduced pressure to collect a fraction of 76 ° C / 4.79 kPa (36 mmHg). If the water content is high, one tenth of the volume of benzene may be added, and water and benzene are distilled off under normal pressure and below 80 ° C, and then dried with magnesium sulfate or cerium oxide, and then distilled under reduced pressure.
10 . Dimethyl sulfoxide <br>Boiling point 189 ° C, melting point 18.5 ° C, density d = 1.100, refractive index n 20D = 1.4783. Dimethyl sulfoxide is miscible with water and can be dried by long-term placement with molecular sieves. Then, it was distilled under reduced pressure, and a fraction of 76 ° C / 1.6 kPa was collected. The temperature during distillation should not exceed 90 ° C, otherwise disproportionation will occur to form dimethyl sulfone and dimethyl sulfide. It may also be dried by using calcium oxide, cerium oxide or anhydrous barium sulfate, and then distilled under reduced pressure. When dimethyl sulfoxide is mixed with certain substances, it may explode, such as sodium hydride, periodic acid or magnesium perchlorate.
11 . Carbon dioxide Carbon dioxide can be produced in a chirp generator using calcium carbonate and dilute hydrochloric acid (1:1). The acid mist is removed by passing the gas through a gas cylinder containing sodium bicarbonate. If drying is required, the gas is passed to another two scrubbers containing concentrated sulfuric acid.
A large amount of carbon dioxide can be used in commercial cylinder gas, and the gas can be dried by two gas cylinders filled with concentrated sulfuric acid, and a small amount of air is present in the carbon dioxide gas.
In order to achieve certain experimental purposes (such as Grignard reaction), solid carbon dioxide (dry ice) can be used. Note that solid carbon dioxide cannot be taken directly by hand without protection, otherwise it will be frostbitten. If you want to use dry ice powder, wrap large chunks of dry ice in a cloth and mash. The carbon dioxide gas can be stably supplied when the dry ice is volatilized, and the appropriate size of dry ice can be placed in the flask, and the generated gas is connected to the reactor through a concentrated sulfuric acid gas cylinder and a safety bottle.
12 . The main use of manganese dioxide in manganese dioxide is to selectively oxidize 1o and 2o alcohols containing allyl and benzyl groups to the corresponding carbonyl compounds. The activity of manganese dioxide varies with the preparation method. Highly active manganese dioxide can be obtained by oxidizing divalent manganese ions with an excess of permanganate under basic conditions:
Dissolve 223 g (1 mol) of manganese sulfate tetrahydrate in 300 mL of water to form solution (a), prepare 240 mL of 40% aqueous solution of sodium hydroxide (b), and then dissolve 190 g (1.2 mol) in 1200 mL of water. Potassium permanganate was stirred with heating, and (a) and (b) were simultaneously added thereto over 1 hour, and finally a pure manganese dioxide brown precipitate was separated. The manganese dioxide is very fine, centrifuged, and thoroughly washed with water until the solution is colorless, and dried at 100 to 120 °C. It is also possible to extend the filtration time as much as possible to remove most of the water, and then distill the remaining water with 150 mL of benzene and 25 g of filter cake. The manganese dioxide reactivity obtained by the precipitation method is sufficient for the direct oxidation reaction. To evaluate the reactivity of a manganese dioxide sample, dissolve 0.25 g of pure phenylpropanol in 50 mL of dry petroleum ether (bp 30-60 ° C), and add 2 g of MnO2 sample previously dried with P2O5. The solution was shaken at room temperature for 2 hours. Filtration, evaporation of the solvent, the product was treated with sulfonic acid salt of 2,4-dinitrophenylhydrazine in methanol. The obtained cinnamaldehyde 2,4-dinitrophenylhydrazine was collected and recrystallized from ethyl acetate. The yield of the highly active manganese dioxide-derived derivative should exceed 0.35 g (60%) and the melting point was 255 °C.
13 . Dioxane <br> Boiling point 104.5 ° C, density d = 1.0336. It is miscible with water, colorless, flammable, and can form an azeotrope with water (content is 81.6%, boiling point 87.8 ° C). It usually contains a small amount of diacetal acetal and water. It can be refluxed with 10% concentrated hydrochloric acid for 3 hours. Nitrogen gas was slowly introduced to remove the generated acetaldehyde. After cooling, the granular potassium hydroxide was added until it was no longer dissolved, the aqueous layer was separated, and dried with granular potassium hydroxide for one day. Filtration, addition of sodium metal reflux for several hours, distillation. The long-lasting dioxane may contain peroxide, which should be removed and then treated.
14 . N,N-dicyclohexylcarbodiimide (DCC; C6H11N=C=NC6H11)
The melting point of 33 ~ 35 ° C, is a waxy low melting point solid, the agent is very corrosive to the skin, it can cause allergies, must be careful when using. High quality DCC (purity 99%) can be purchased, and the reagent bottle can be liquefied in a small amount of hot water for weighing.
This reagent is often used as a dehydrating agent and is removed as a dicyclohexylurea after the reaction. The recovered dicyclohexylurea (mp 234 ° C) can be recrystallized from ethanol and then converted to DCC by reaction with p-toluenesulfonyl chloride, phosphorus oxychloride or phosphorus pentoxide in a pyridine solution: 17.1 g (47 mL) with stirring. , 0.11 mol) of phosphorus oxychloride was added dropwise to a solution of 22.5 g (0.1 mol) of dicyclohexylurea in 50 mL of pyridine, and then heated to 60-90 ° C for 1.5 hours, and the reaction product was poured on crushed ice. The mixture was extracted with petroleum ether (bp 60-80 ° C), dried over anhydrous sodium sulfate, and then evaporated. The yield of the diimide is about 14 g (68%), bp 157 to 159 ° C / 2.0 kPa (131 ° C / 0.5 kPa).
15 . Potassium Fluoride <br>Anhydrous Potassium Fluoride can be prepared by the following steps: potassium fluoride crystals are finely ground, heated to 180-210 ° C with a heating mantle, and stored in a desiccator. Potassium fluoride was dried for three hours before use and then ground in a heated mortar (50 ° C).
16 . Chromium oxidants Cr(VI) is widely used as an oxidant in organic chemistry. Chromium oxide is a deliquescent red crystal that is easily soluble in water and sulfuric acid. It is a strong oxidant and must be handled with care. It is usually used in its acetic acid or acetic anhydride solution. Adding chromium oxide to ice-cold acetic anhydride can be formulated into a solution of chromium oxide in acetic anhydride. It is important not to add an acid anhydride to the chromium oxide. Adding the acid anhydride to a large amount of chromium oxide causes explosive decomposition. In the reaction of oxidizing a simple primary alcohol to an aldehyde, a secondary alcohol to a ketone, and an alkylborane to a ketone, an aqueous solution of sodium dichromate in sulfuric acid may also be used as the oxidizing agent. Since the aldehyde formed by the oxidation of the primary alcohol is continuously oxidized to a carboxylic acid, the acid chromate is generally not used to oxidize the primary alcohol to form an aldehyde. Cr(VI) can be selectively oxidized in an inert medium. Currently, Cr(VI) pyridine complexes (dichromate pyridinium and chlorochromate pyridinium) are widely used in primary alcohols and acid-sensitive group alcohols. Selective oxidation.
The step of oxidizing the primary alcohol and the secondary alcohol with dichromate pyridinium salt is: adding 6 g (60 mmol) of chromium trioxide to 150 mL of pyridine containing 9.49 g (12 mmol) of dichloromethane under magnetic stirring. Then, the flask was stoppered with a drying tube containing a desiccant, the solution was dark purple, stirred for 15 min, and a part of an alcohol solution (10 mmol) dissolved in a small amount of dichloromethane was added at the end of stirring, and a black precipitate was observed immediately. When the temperature of the solution was kept at room temperature, stirring was continued for 15 min. At this time, the solution and the residue were separated, and the residue was washed with 200 mL of diethyl ether. The organic layer was washed three times with three 100 mL portions of 5% aqueous NaOH solution, once with 100 mL of 5% aqueous HCl solution, once with 100 mL of 5% aqueous NaHCO3 solution, once with 100 mL of a saturated aqueous solution of NaCl, and then dried over magnesium sulfate. Finally, the layered methylene chloride was concentrated, and the residue was extracted with diethyl ether. The insoluble chromium salt was filtered, washed with dilute alkali and saturated brine, dried over magnesium sulfate, and evaporated to give a crude product of aldehyde and ketone. . The alcohol which can be oxidized by such a procedure is 2-octanol (97% yield of carbonyl compound), 1-octanol (90%), benzyl alcohol (89%), borneol (89%), cinnamyl alcohol (96). %).
Pyridinium chlorochromate is formed by the action of chromium trioxide and pyridine in the presence of hydrochloric acid. It has a weak acidity and easily reacts with a basic group, and it can replace the oxidic acid dichromate pyridinium salt. The pyridinium chlorochromate can be prepared by the following method: 100 g (1 mol) of chromium oxide (VI) is rapidly added to 184 mL of 6 mol?L-1 HCl (1.1 mol) during stirring, and the solution is cooled after 5 min. To 0 ° C, carefully add 79.1 g (1 mol) of pyridine (at least 10 min), re-cooled to 0 ° C, to give an orange-yellow solid, the solid was placed in a fritted glass funnel, and dried in vacuo for 1 hour to give the product 188.8 g (84%). It is not easy to measure whether the solid is completely dry with a moisture analyzer, so it needs to be left at room temperature for a while. The pyridinium chlorochromate can oxidize 1-heptanol to heptaldehyde.
The pyridinium chlorochromate adsorbed on alumina in some reactions is more effective. At 40 ° C, 6 g of chromium trioxide dissolved in 11 mL of hydrochloric acid (6 mol? L-1), 4.75 g of pyridine was added within 10 min, the solution was cooled to below 10 ° C until an orange-yellow solid formed, and then heated to 40 At ° C, the solid was dissolved, 50 g of alumina was added under stirring, the temperature was kept at 40 ° C, and the solvent was evaporated to give an orange solid, which was dried in vacuo for 2 hr. The reagent can be stored in a vacuum desiccator for several weeks in the dark, and its activity is unchanged.
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