Preparation of ethyl acetate, in-depth expansion of core test points + preparation of ethyl acetate in the real questions of the college entrance examination, in-depth expansion of core test points + analysis of the real questions of the college entrance examination

Preparation of ethyl acetate Preparation of ethyl acetate

The preparation of organic ethyl acetate occupies a very important position in the college entrance examination. In recent years, it has appeared frequently in the college entrance examination questions in various provinces. The following is an analysis of the test centers of ethyl acetate and the real questions about this test center over the years. The preparation of organic ethyl acetate occupies a very important position in the college entrance examination. In recent years, it has appeared frequently in the college entrance examination questions in various provinces. The following is an analysis of the test centers of ethyl acetate and the real questions about this test center over the years.

[Test Center Breakthrough] [Test Center Breakthrough]

Experimental Principle Experimental Principle

Formula for the preparation of ethyl acetate: Formula for the preparation of ethyl acetate: CHA3COOH + CA2HA5OH − Concentrated HA2SOA4 Delta CHA3COOCA2HA5 + HA2O

Principle Deep Expansion (College Entrance Examination Deep Dig Test Center) Principle Deep Expansion (College Entrance Examination Deep Dig Test Center) : This reaction belongs to: This reaction belongs to nucleophilic substitution reaction (acyl substitution) nucleophilic substitution reaction (acyl substitution) , not a simple acid-base neutralization. The core mechanism of the reaction is: concentrated sulfuric acid protons carbonyl oxygen of acetic acid, enhances the positive electricity of carbonyl carbon, makes ethanol hydroxyl oxygen attack carbonyl carbon as a nucleophilic reagent, and generates esters and water through the addition-elimination process. The college entrance examination often implicit examination mechanism misunderstanding: In the reaction, it is not a simple acid-base neutralization. The core mechanism of the reaction is: concentrated sulfuric acid protons carbonyl oxygen of acetic acid, enhances the positive electricity of carbonyl carbon, and makes ethanol hydroxyl oxygen attack carbonyl carbon as a nucleophilic reagent, and generates ester and water through the addition-elimination process. The common hidden investigation mechanism of the college entrance examination: the water molecule removed by in the reaction is "acetic acid dehydroxy, ethanol dehydrogenation" , which can be verified by isotope tracer method (A18A2218O labeled ethanol), which is a high-frequency trap point for multiple-choice college entrance examination questions. At the same time, the equilibrium movement law of this reversible reaction is the core basis for experimental optimization, and all experimental operation details are centered on "promoting equilibrium forward movement and improving yield". Labelled ethanol) verification, which is the high-frequency trap point of the multiple-choice questions in the college entrance examination. At the same time, the equilibrium movement law of the reversible reaction is the core basis for experimental optimization, and all the experimental operation details are centered on "promoting the positive balance movement and improving the yield".

Experimental steps Experimental steps

Add 3mL of ethanol to a test tube, then slowly add 2mL of concentrated sulfuric acid and 2mL of acetic acid while shaking the test tube. Connect the device as shown in the figure, slowly heat it with an alcohol lamp, and pass the generated vapor through the conduit to the liquid surface of the saturated sodium carbonate solution to observe the phenomenon. Add 3mL of ethanol to a test tube, and then slowly add 2mL of concentrated sulfuric acid and 2mL of acetic acid while shaking the test tube. Connect the device as shown in the figure, slowly heat it with an alcohol lamp, and pass the generated vapor through the conduit to the liquid surface of the saturated sodium carbonate solution to observe the phenomenon.

Professional interpretation of steps Professional interpretation of steps : The essence of the reagent addition sequence is: The essence of the reagent addition sequence is Anti-explosion, anti-volatilization, anti-side reaction Anti-explosion, anti-volatilization, and anti-side reaction . Ethanol has the smallest density, low boiling point, and strong volatility. Adding ethanol first can be used as a dilution medium to avoid local overheating when mixed directly with acetic acid; concentrated sulfuric acid is slowly added dropwise and continuously shaken to uniformly dissipate heat and prevent side reactions such as carbonization of ethanol, elimination, and intermolecular dehydration caused by local high temperature; finally, acetic acid is added to minimize the premature volatilization loss of acetic acid, which is in line with the optimization logic of raw material utilization for reversible reactions... Ethanol has the smallest density, low boiling point and strong volatility. Adding ethanol first can be used as a dilution medium to avoid local overheating of concentrated sulfuric acid mixed directly with acetic acid. Concentrated sulfuric acid is slowly added dropwise and continuously oscillated to uniformly dissipate heat and prevent local high temperature from causing side reactions such as ethanol carbonation, elimination, and intermolecular dehydration. Finally, acetic acid is added to minimize the early volatilization loss of acetic acid, which is in line with the optimization logic of raw material utilization for reversible reactions.

Precautions Precautions

(1) Mixing of reactants: first ethanol, then concentrated sulfuric acid (adding broken porcelain to prevent boiling), finally acetic acid, and then heating. (1) Mixing of reactants: first ethanol, then concentrated sulfuric acid (adding broken porcelain to prevent boiling), finally acetic acid, and then heating.

(2) Concentrated sulfuric acid is used as both a catalyst and a water absorber. The amount of concentrated sulfuric acid used for catalysis is very small. Generally, the amount of concentrated sulfuric acid can be completed as long as the mass of sulfuric acid reaches 3% of the mass of ethanol, but in order to remove the water generated in the reaction, the amount of concentrated sulfuric acid should be slightly more. (2) Concentrated sulfuric acid is used as both a catalyst and a water absorber. The amount of concentrated sulfuric acid used for catalysis is very small. Generally, the mass of sulfuric acid can be completed as long as the mass of sulfuric acid reaches 3% of the mass of ethanol, but in order to remove the water generated in the reaction, the amount of concentrated sulfuric acid should be slightly

(3) When preparing ethyl acetate, the reaction temperature should not be too high. It should be kept at about 60 ℃~ 70 ℃. When the temperature is too high, impurities such as ether and sulfur dioxide will be generated. After the liquid is heated to boiling, it should be heated with a low fire. Several pieces of broken porcelain can be added to the test tube in advance to prevent the liquid from boiling. (3) When preparing ethyl acetate, the reaction temperature should not be too high. It should be kept at about 60 ℃~ 70 ℃. When the temperature is too high, impurities such as ether and sulfur dioxide will be generated. After the liquid is heated to boiling, it should be heated with a low fire instead. Several pieces of broken porcelain can be added to the test tube in advance to prevent the liquid from boiling.

(4) The inclined airway is longer, which plays the role of gas conduction and condensation at the same time; (4) The inclined airway is longer, which plays the role of gas conduction and condensation at the same time;

(5) Do not extend the airway into the sodium carbonate solution to prevent the sodium carbonate solution from being sucked into the test tube heating the reactant due to uneven heating. (5) Do not extend the airway into the sodium carbonate solution to prevent the sodium carbonate solution from being sucked into the test tube heating the reactant due to uneven heating.

(6) The functions of saturated sodium carbonate solution are: ① Condensing ester vapor to reduce the solubility of the ester in water (conducive to stratification); ② Dissolving ethanol mixed in ethyl acetate. ③ Can react with volatile acetic acid to generate sodium acetate, which is convenient for smelling the fragrance of ethyl acetate. (6) The functions of saturated sodium carbonate solution are: ① Condensing ester vapor to reduce the solubility of the ester in water (conducive to stratification); ② Dissolving ethanol mixed in ethyl acetate. ③ Can react with volatile acetic acid to generate sodium acetate, which is convenient for smelling the fragrance of ethyl acetate.

(7) Reasons for not using base (NaOH) with sodium carbonate: Although sodium hydroxide can also absorb acetic acid and ethanol, the base will catalyze the complete hydrolysis of ethyl acetate, resulting in the failure of the experiment. (7) Reasons for not using base (NaOH) with sodium carbonate: Although sodium hydroxide can also absorb acetic acid and ethanol, the base will catalyze the complete hydrolysis of ethyl acetate, resulting in the failure of the experiment.

(8) The esterification reaction is a reversible reaction. In order to increase the yield of esters, an excess of one of the reactant acids and alcohols is generally used. In the laboratory, an excess of ethanol is generally used. The mass fraction of ethanol is higher, and it is better to use absolute ethanol instead of ethanol with a mass fraction of 95%. (8) The esterification reaction is a reversible reaction. In order to increase the yield of esters, an excess of one of the reactant acids and alcohols is generally used. In the laboratory, an excess of ethanol is generally used. The mass fraction of ethanol is higher, and it is better to use absolute ethanol instead of ethanol with a mass fraction of 95%.

(9) In order to facilitate the formation of ethyl acetate, the following measures can be taken: ① When preparing ethyl acetate, the reaction temperature should not be too high. Do not make the liquid boil. ② It is best to use glacial acetic acid and absolute ethanol. At the same time, the method of excessive ethanol should be used. ③ The amount of concentrated sulfuric acid should be slightly more than the amount of ethanol. (9) In order to facilitate the formation of ethyl acetate, the following measures can be taken: ① When preparing ethyl acetate, the reaction temperature should not be too high. Do not make the liquid boil. ② It is best to use glacial acetic acid and absolute ethanol. At the same time, the method of excessive ethanol should be used. ③ The amount of concentrated sulfuric acid should be slightly more than the amount

[In-depth expansion: high-level core test points for the college entrance examination (exclusive refinement, no repetition) ] [In-depth expansion: high-level core test points for the college entrance examination (exclusive refinement, no repetition) ]

1. The underlying logic and propositional traps of reagent selection 1. The underlying logic and propositional traps of reagent selection

Many examinees only memorize the three functions of "saturated sodium carbonate", but ignore the underlying logic of the college entrance examination core test method. First, many examinees only memorize the three functions of "saturated sodium carbonate", but ignore the underlying logic of the college entrance examination core test method. First, must use saturated solution rather than dilute solution must use saturated solution rather than dilute solution : The high ionic concentration of saturated sodium carbonate solution can greatly reduce the salinity effect of ethyl acetate and minimize the solubility of esters; if dilute solution is used, the dissolution loss of esters is greatly increased and the yield is reduced. This is a high-frequency test point for experimental error analysis. Second, the saturated sodium carbonate solution has a high ion concentration, which can greatly reduce the salt-soluble effect of ethyl acetate and minimize the solubility of the ester; if a dilute solution is used, the dissolution loss of the ester increases significantly and the yield decreases, which is a high-frequency test point for experimental error analysis. Second, the hidden reasons for disabling sodium bicarbonate to replace sodium carbonate The hidden reasons for disabling sodium bicarbonate to replace sodium carbonate : sodium bicarbonate has low solubility, low concentration, and the efficiency of removing acetic acid is weaker than that of sodium carbonate, and the reaction generates: sodium bicarbonate has small solubility and low concentration, and the efficiency of removing acetic acid is weaker than that of sodium carbonate. Moreover, the COA2 generated by the reaction easily leads to foaming on the liquid surface, causing the ester layer to be layered and cloudy, which interferes with the observation of Third, the dual action weights of concentrated sulfuric acid are different: the catalytic action is the whole process, the water absorption is balanced regulation, and the water absorption removes the product water, which is the key to the positive movement of the reversible reaction, and is also the core reason for the excess of concentrated sulfuric acid, rather than the simple catalytic demand. It is easy to cause the liquid surface to bubble, causing the ester layer to be layered and turbid, which interferes with the observation of experimental phenomena. Third, the dual action weights of concentrated sulfuric acid are different: the catalytic action is the whole process, the water absorption is balanced regulation, and the water absorption removes the product water, which is the key to the positive movement of the reversible reaction. It is also the core reason for the excess of concentrated sulfuric acid, rather than the simple catalytic demand.

2. Professional principles and anomaly analysis of device design 2. Professional principles and anomaly analysis of device design

The conventional test center only mentions that the catheter does not extend into the liquid surface to prevent reverse suction, and the depth is expanded: The conventional test center only mentions that the catheter does not extend into the liquid surface to prevent reverse suction, and the depth is expanded: The double incentive of reverse suction in this experiment , one is that uneven heating causes a sudden drop in pressure in the reactor, and the other is that acetic acid and ethanol vapor are very soluble in aqueous solution, and the gas quickly dissolves in a short time to cause negative pressure. At the same time, the long catheter condenses, one is that uneven heating causes a sudden drop in pressure in the reactor, and the other is that acetic acid and ethanol vapor are very soluble in aqueous solution, and the gas quickly dissolves in a short time to cause negative pressure. At the same time, the long duct condensation is air condensation air condensation , which belongs to the simple condensation device and is suitable for the system with low boiling point of ethyl acetate (77 ° C); if the preparation of high boiling point esters (such as isoamyl acetate in the real question), it must be converted to condensation pipe condensation, which is the general rule of device selection and the migration test point of the college entrance examination., belongs to the simple condensation device, which is suitable for the system with low boiling point of ethyl acetate (77 ° C); if the preparation of high boiling point esters (such as isoamyl acetate in the real question), it must be converted to condensation pipe condensation, which is the general rule of device selection and the migration test point of the college entrance examination.

Depth analysis of common abnormal phenomena: The ester layer collected in the experiment is turbid, not a failure of the experiment. The core reason is that the ester layer is mixed with tiny water droplets and is not completely delaminated. Subsequent addition of anhydrous inorganic salt desiccant can be clarified. If the ester layer is too small and the yield is low, the main sources of error are: high temperature, volatilization of raw materials, consumption of reactants by side reactions, dissolution of some esters in sodium carbonate solution, insufficient condensation of ducts, etc. In-depth analysis of common abnormal phenomena: The ester layer collected in the experiment is turbid, not a failure of the experiment. The core reason is that the ester layer is mixed with tiny water droplets and is not completely delaminated. Subsequent addition of anhydrous inorganic salt desiccant can be clarified; if the ester layer is too small and the yield is low, the main sources of error are: high temperature raw material volatilization, side reaction consumption of reactants, sodium carbonate solution to dissolve part of the ester, insufficient condensation of the catheter, etc.

3. Equilibrium and kinetic dual regulation of reaction conditions 3. Equilibrium and kinetic dual regulation of reaction conditions

Core trend of the college entrance examination proposition: from "memory operation" to "understanding regulation logic". The esterification reaction is simultaneously affected by the core trend of the college entrance examination proposition: from "memory operation" to "understanding regulation logic". The esterification reaction is simultaneously affected by the kinetic rate kinetic rate and the thermodynamic equilibrium thermodynamic equilibrium . Heating up can accelerate the reaction rate (kinetics), but too high temperature will exacerbate the volatilization of raw materials and the occurrence of side reactions, and the esterification reaction exotherms, and heating up will inhibit the positive shift of equilibrium (thermodynamics). Therefore, the experiment chooses low temperature and low heat heating, which is the best compromise between rate and equilibrium. Double effect. Heating can accelerate the reaction rate (kinetics), but too high temperature will exacerbate the volatilization of raw materials and the occurrence of side reactions, and the esterification reaction will exothermic, and heating will inhibit the forward movement of equilibrium (thermodynamics). Therefore, the experiment chooses low temperature and low fire heating, which is the optimal compromise between rate and equilibrium.

Selection logic of excess raw materials: The laboratory chooses excess ethanol instead of excess acetic acid, not random selection, the core reason is the selection logic of excess raw materials: The laboratory chooses excess ethanol instead of excess acetic acid, not random selection, the core reason is Ethanol has a lower boiling point, stronger volatility, lower cost Ethanol has a lower boiling point, stronger volatility, and lower cost . Acetic acid has a higher price and controllable volatilization loss. Excessive ethanol can promote the positive movement of the balance at a low cost and maximize the conversion rate of expensive raw materials acetic acid. This is the general material selection logic for industrial and laboratory preparation, and it is also a necessary hidden knowledge point for yield calculation and experimental optimization questions... The price of acetic acid is higher, the volatilization loss is controllable, and excessive ethanol can promote the positive balance at low cost, maximizing the conversion rate of expensive raw material acetic acid. This is a general material selection logic for industrial and laboratory preparation, and it is also a necessary hidden knowledge point for yield calculation and experimental optimization questions.

4. Side reaction system and experimental error traceability (college entrance examination difficulties) 4. Side reaction system and experimental error traceability (college entrance examination difficulties)

The core side reactions of unrefined textbooks are the high-frequency test points for multiple-choice questions and experimental inquiry questions in the college entrance examination: ① Intramolecular dehydration of ethanol to produce ethylene (170 ° C) and intermolecular dehydration to generate ether (140 ° C), so strict temperature control 60-70 ° C can completely avoid two types of side reactions; ② Strong oxidizing side reactions of concentrated sulfuric acid: concentrated sulfuric acid oxidizes ethanol and acetic acid at high temperature to generate core side reactions that have not been refined in textbooks, which is the high-frequency test point for multiple-choice questions and experimental inquiry questions in the college entrance examination: ① Intramolecular dehydration of ethanol to produce ethylene (170 ° C) and intermolecular dehydration to generate ether (140 ° C), so strict temperature control of 60-70 ° C can completely avoid two types of side reactions; ② Strong oxidizing side reactions of concentrated sulfuric acid: oxidation of concentrated sul Ethanol and acetic acid generate SOA2 and COA2 impurities, resulting in the mixture of acidic impurities and solution discoloration of the product; ③ Ester hydrolysis side reactions: Excessive temperature and alkaline environment will accelerate the hydrolysis of the ester and reduce the yield. All error analyses of low yield and impure products can be carried out around the above side reactions. Impurities cause the product to be mixed with acidic impurities and discoloration of the solution; ③ Ester hydrolysis side reactions: Excessive temperature and alkaline environment will accelerate the hydrolysis of the ester and reduce the yield. All error analyses of low yield and impure products can be carried out around the above side reactions.

5. The complete process of product separation and purification (extended college entrance examination test center) 5. The complete process of product separation and purification (extended college entrance examination test center)

The basic experiment only examines stratified liquid separation, and the college entrance examination often expands the basic experiment only examines stratified liquid separation. The college entrance examination often expands the complete purification process of ethyl acetate . The complete purification process of ethyl acetate is a high-frequency test method for the big problem: after the reaction, the mixed liquid → saturated sodium carbonate washing (except acetic acid, sulfuric acid, ethanol) → standing liquid separation (taking the upper organic layer) → anhydrous sodium sulfate/magnesium sulfate drying (except for trace water) → filtering (except desiccant solids) → distillation (collecting fractions at 77 ° C to obtain pure products). Core details: Drying must be done before distillation. If distilled first and then dried, water vapor will be mixed into the fraction, and anhydrous pure esters cannot be obtained. When separating liquids, keep in mind that "esters are light and heavy, up and down" to avoid misunderstandings in liquid separation operations., High-frequency test method for the big question: mixed liquid after reaction → saturated sodium carbonate washing (except acetic acid, sulfuric acid, ethanol) → standing liquid separation (take the upper organic layer) → anhydrous sodium sulfate/magnesium sulfate drying (except for trace water) → filtering (except desiccant solids) → distillation (collect fractions at 77 ° C to obtain pure products). Core details: Drying must be done before distillation. If distilled first and then dried, water vapor will be mixed into the fraction, and anhydrous pure esters cannot be obtained. When separating the liquid, keep in mind that "the ester is light and the water is heavy, up and down" to avoid the misunderstanding of liquid separation operation.

[College Entrance Examination Real Questions] [College Entrance Examination Real Questions]

2015 Jiangsu Volume 2015 Jiangsu Volume

The experimental scheme designed below can achieve the experimental purpose () The experimental scheme designed below can achieve the experimental purpose ()

A. Preparation of Al (OH) 🥰 Suspension: Add an excess of 6mol · L ¬ NaOH solution to 1mol · L ¬ AlCl 🥰 Solution A. Preparation of Al (OH) 🥰 Suspension: Add an excess of 6mol · L ¬ NaOH solution to 1mol · L ¬ AlCl 🥰 Solution

B. Purification of ethyl acetate containing a small amount of acetic acid: Add an excess of saturated sodium carbonate solution to ethyl acetate containing a small amount of acetic acid, shake and let stand to separate and remove the water from the organic phase B. Purification of ethyl acetate containing a small amount of acetic acid: Add an excess of saturated sodium carbonate solution to ethyl acetate containing a small amount of acetic acid, shake and let stand to separate and remove the water from the organic phase

C. Test whether the solution contains Fe ³: Take a small amount of the solution to be tested, add a small amount of new chlorine water to it, and then add KSCN solution dropwise to observe the experimental phenomenon C. Test whether the solution contains Fe ³: Take a small amount of the solution to be tested, add a small amount of new chlorine water to it, and then add KSCN solution dropwise to observe the experimental phenomenon

D. Explore the effect of catalysts on the decomposition rate of H _ 2O _ 2: Under the same conditions, add 2 ml of 5% H _ 2O _ 2 and 1 ml of H _ 2O _ 2 to one test tube, and add 2 mL of 5% H _ 2O _ 2 and 1 mL of FeCl _ 2 to another test tube to observe and compare experimental phenomena D. Explore the effect of catalysts on the decomposition rate of H _ 2O _ 2: Under the same conditions, add 2 ml of 5% H _ 2O _ 2 and 1 ml of H _ 2 to one test tube, and add 2 mL of 5% H _ 2O _ 2 and 1 mL of FeCl _ 2 to another test tube to observe and compare experimental phenomena.

Answer Answer : BD: BD

Analytical analysis : A, Al (OH) is a catalyst, which accelerates the reaction rate, so it is correct.: A, Al (OH) is an amphoteric hydroxide, which can react with excess sodium hydroxide Sodium aluminate is raw, so aluminum hydroxide suspension cannot be prepared, which is wrong; B, the acidity of acetic acid is stronger than that of sodium carbonate, saturated sodium carbonate removes acetic acid, and can also reduce the solubility of ethyl acetate to precipitate, and then separate the liquid, so it is correct; C, chlorine water has strong oxidation, and may oxidize Fe ² to Fe ³, which will also occur, so it is wrong; D, two test tubes do a comparative experiment. If the second test tube produces more bubbles than the first one, it means that FeCl is a catalyst, which accelerates the reaction rate, so it is correct.

True question depth expansion True question depth expansion : Option B is the motif of the college entrance examination purification question type, core extension test point: Purification of ethyl acetate: Option B is the motif of the college entrance examination purification question type, core extension test point: Purification of ethyl acetate Absolutely cannot use NaOH solution Absolutely cannot use NaOH solution , NaOH can catalyze the hydrolysis of ethyl acetate at room temperature, resulting in product loss; can not be purified with distilled water, because ethyl acetate is slightly soluble in water, the impurity removal efficiency is extremely low and the product loss. At the same time, "removing the water from the organic phase" is a key step in purification, corresponding to the above-mentioned extended drying operation, which is a score point missed by many candidates and the core embodiment of the rigor of the experiment., NaOH can catalyze the hydrolysis of ethyl acetate at room temperature, resulting in product loss; it cannot be purified with distilled water, because ethyl acetate is slightly soluble in water, the impurity removal efficiency is extremely low and the product is lost. At the same time, "removing the water from the organic phase" is a key step in purification, corresponding to the above-mentioned extended drying operation, which is a score point missed by many candidates and the core embodiment of the rigor of the experiment.

2014 National New Curriculum Standard I 2014 National New Curriculum Standard I

Isoamyl acetate is one of the constituents of bee pheromones and has the fragrance of rubber. The reaction, device schematic diagram and related information for laboratory preparation of isoamyl acetate are as follows: Isoamyl acetate is one of the constituents of bee pheromones and has the fragrance of rubber. The reaction, device schematic diagram and related information for laboratory preparation of isoamyl acetate are as follows:

Experimental steps: Experimental steps:

Add 4.4 g of isoamyl alcohol, 6.0 g of acetic acid, a few drops of concentrated sulfuric acid, and 2 to 3 pieces of broken porcelain to A, start heating A slowly, reflux for 50 minutes, and after the reaction liquid is cooled to room temperature, pour it into a separation funnel, wash it with a small amount of water, a saturated sodium bicarbonate solution, and water respectively. Add a small amount of anhydrous magnesium sulfate solid to the separated product, let it stand for a while, filter to remove the magnesium sulfate solid, and purify it by distillation. Collect a fraction of 140 to 143 ° C to obtain isoamyl acetate 3.9 g. Answer the following questions: Add 4.4 g of isoamyl alcohol, 6.0 g of acetic acid, a few drops of concentrated sulfuric acid, and 2 to 3 pieces of broken porcelain to A, start heating A slowly, reflux for 50 minutes, and after the reaction liquid is cooled to room temperature, pour it into a separation funnel, wash it with a small amount of water, saturated sodium bicarbonate solution, and water respectively. Add a small amount of anhydrous magnesium sulfate solid to the separated product, let it stand for a while, filter to remove the magnesium sulfate solid, carry out distillation and purification, and collect fractions at 140 to 143 ° C to obtain isoamyl acetate 3.9 g. Answer the following questions:

(1) The name of device B is: (1) The name of device B is:

(2) In the washing operation, the main purpose of the first washing is:; The main purpose of the second washing is:. (2) In the washing operation, the main purpose of the first washing is:; The main purpose of the second washing is:.

(3) In the washing and liquid separation operation, it should be fully shaken and then left to stand, after delamination (fill in the label), (3) In the washing and liquid separation operation, it should be fully shaken and then left to stand, after delamination (fill in the label),

A. Pour isoamyl acetate directly from the top of the separation funnel A. Pour isoamyl acetate directly from the top of the separation funnel

B. Directly release isoamyl acetate from the lower mouth of the separation funnel B. Directly release isoamyl acetate from the lower mouth of the separation funnel

C. First release the water layer from the lower port of the separation funnel, and then release the isoamyl acetate from the lower port C. First release the water layer from the lower port of the separation funnel, and then release the isoamyl acetate from the lower port

D. First release the water layer from the lower port of the separation funnel, and then release the isoamyl acetate from the upper port D. First release the water layer from the lower port of the separation funnel, and then release the isoamyl acetate from the upper port

(4) The purpose of adding excess acetic acid in this experiment is: (4) The purpose of adding excess acetic acid in this experiment is:

(5) The purpose of adding a small amount of anhydrous magnesium sulfate in the experiment is: (5) The purpose of adding a small amount of anhydrous magnesium sulfate in the experiment is:

(6) In the distillation operation, the instrument selection and installation are correct: (fill in the label) (6) In the distillation operation, the instrument selection and installation are correct: (fill in the label)

(7) The yield of this experiment is: (7) The yield of this experiment is:

A, 30% B, 40% C, 50% D, 60% A, 30% B, 40% C, 50% D, 60%

(8) During the distillation operation, if the distillate is collected from 130 ° C, the yield is biased (high or low) because (8) During the distillation operation, if the distillate is collected from 130 ° C, the yield is biased (high or low) because

Answer Answer :

(1) Spherical condenser (1) Spherical condenser

(2) Wash off most of the concentrated sulfuric acid and acetic acid; wash off the sodium bicarbonate. (2) Wash off most of the concentrated sulfuric acid and acetic acid; wash off the sodium bicarbonate.

(3) d. (3) d.

(4) Increase the conversion rate of isoamyl alcohol (4) Increase the conversion rate of isoamyl alcohol

(5) Dry (5) Dry

(6) b (6) b

(7) c (7) c

(8) High, a small amount of unreacted isoamyl alcohol will be collected. (8) High, a small amount of unreacted isoamyl alcohol will be collected.

Parsing Parsing :

(1) Instrument B is a spherical condenser tube (1) Instrument B is a spherical condenser tube

(2) The first wash mainly washes off concentrated sulfuric acid and excess acetic acid. The second wash mainly washes off the saturated NaHCO added in the previous step. Mainly consider the solubility of the substance and the presence of impurities. (2) The first wash mainly washes off concentrated sulfuric acid and excess acetic acid. The second wash mainly washes off the saturated NaHCO added in the previous step. Mainly consider the solubility of the substance and the presence of impurities.

(3) Isoamyl acetate is lighter than water. When separating, the lower layer must be released from the lower port, and the upper liquid must be poured out from the upper port. So choose d. (3) Isoamyl acetate is lighter than water. When separating, the lower layer must be released from the lower port, and the upper liquid must be poured out from the upper port. So choose d.

(4) Due to the lowest boiling point of acetic acid, there will be more volatile loss of acetic acid. Adding excess acetic acid can ensure that more isoamyl alcohol is converted into products (4) Due to the lowest boiling point of acetic acid, there will be more volatile loss of acetic acid. Adding excess acetic acid can ensure that more isoamyl alcohol is converted into products

(5) Anhydrous MgSO has fast water absorption and does not react with isoamyl acetate, which can absorb water for the next distillation. (5) Anhydrous MgSO has fast water absorption and does not react with isoamyl acetate, which can absorb water for the next distillation.

(6) The position of the thermometer of a and d is wrong, and the condensation pipe should use a straight condenser pipe. If a spherical condenser pipe is used, the condensed liquid cannot all flow down, so b should be used. (6) The position of the thermometer of a and d is wrong, and the condensation pipe should use a straight condenser pipe. If a spherical condenser pipe is used, the condensed liquid cannot all flow down, so b should be used.

(7) If an excess of acetic acid can be seen from the reaction equation, it is calculated as isoamyl alcohol. Theoretically, isoamyl acetate can be generated 6.6g. The yield is: 3.9g/6.5g × 100% = 60%. (7) If an excess of acetic acid can be seen from the reaction equation, it is calculated as isoamyl alcohol. Theoretically, isoamyl acetate can be generated 6.6g. The yield is: 3.9g/6.5g × 100% = 60%.

(8) Will make the yield higher, and the isoamyl alcohol soluble in isoamyl acetate will enter the product. (8) Will make the yield higher, and the isoamyl alcohol soluble in isoamyl acetate will enter the product.

Deep Expansion of True Questions (College Entrance Examination Migration Thinking) Deep Expansion of True Questions (College Entrance Examination Migration Thinking) : This question is the final motif of the college entrance examination for esterification reaction, which perfectly reflects the logic of the college entrance examination proposition of "Basic Experiment Migration Unfamiliar Ester Preparation". First,: This question is the final motif of the college entrance examination for esterification reaction, which perfectly reflects the logic of the college entrance examination proposition of "Basic Experiment Migration Unfamiliar Ester Preparation". First, Core Law of Condenser Tube Selection Core Law of Condenser Tube Selection : Use a spherical condenser tube for reflux reaction (heating reflux in this question) to increase the condensation contact area, and the condensation effect is good; use a straight condenser tube for distillation and purification to avoid liquid retention in the pipe wall. This is the absolute test point for instrument selection, and all organic experiments are universal Second, the washing process layer logic: washing with water to remove strong acids, soluble organic acids, weak alkaline solutions to remove residual weak acids, secondary washing to remove residual salts, layer by layer to remove impurities, to avoid impurity residues, is a general process of organic purification. Third, the nature of yield error: collect fractions in advance and mix them with low boiling point impurities, which belong to: use a spherical condenser tube for reflux reaction (heating reflux in this question) to increase the condensation contact area, and the condensation effect is good; use a straight condenser tube for distillation and purification to avoid liquid retention in the tube wall, which is an absolute test point for instrument selection, and is universal for all organic experiments. Second, the washing process layer logic: washing with water to remove strong acids, soluble organic acids, weak alkaline solutions to remove residual weak acids, secondary washing to remove residual salts, layer by layer to remove impurities, to avoid impurity residues, is a general process of organic purification. Third, the nature of yield error: collecting fractions in advance mixed with low boiling point impurities belongs to false high physical yield false high physical yield , not the increase in reaction conversion rate, is the concept of high-frequency error-prone analysis point of the college entrance examination, which is different from the decrease in yield caused by side reactions., is not the increase in reaction conversion rate, but the concept of high-frequency error-prone analysis point of the college entrance examination, which is different from the decrease in yield caused by side reactions.

[Ultimate Proposition Law Summary (Exclusive) ] [Ultimate Proposition Law Summary (Exclusive) ]

1. Proposition trend: Abandon simple memory test questions, focus on 1. Proposition trend: Abandon simple memory test questions, focus on principle transfer, operation logic, error analysis, unfamiliar ester preparation principle transfer, operation logic, error analysis, unfamiliar ester preparation , using ethyl acetate experiment as a template to examine the general law of similar esterification reactions., using ethyl acetate experiment as a template to examine the general law of similar esterification reactions.

2. High-frequency demarcation points: confusion of isotope tracer mechanism, confusion of desiccant and impurity remover effect, condenser selection error, yield error causal inversion, incorrect operation sequence of liquid separation. 2. High-frequency demarcation points: confusion of isotope tracer mechanism, confusion of desiccant and impurity remover effect, incorrect selection of condenser tube, yield error causal inversion, incorrect operation sequence of liquid separation.

3. Problem-solving core thinking: All operations, reagents, and devices are selected around 3. Problem-solving core thinking: All operations, reagents, and devices are selected around to accelerate the reaction rate, promote the positive movement of the balance, reduce the loss of raw materials, avoid side reactions, efficient impurity removal and purification to accelerate the reaction rate, promote the positive movement of the balance, reduce the loss of raw materials, avoid side reactions, and efficient impurity removal and purification The five core logics are expanded to solve all esterification reaction experimental problems universally. The five core logics are expanded to solve all esterification reaction experimental problems universally.

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