基础综合化学实验佟庆笑汕头大学理学院化学系2011年
基础综合化学实验 佟庆笑 汕头大学理学院化学系 2011 年 1
目 录实验一、溴代环已烷的制备实验二、乙酰苯胺的制备.6实验三、从茶叶中提取咖啡因....8实验四、配合物键合异构体的制备及红外光谱测定..14实验五、离子型化合物的离子交换分离..1921实验六、常见有机化合物的化学鉴别实验七、乙酰二茂铁的制备与分离，222
目 录 实验一、溴代环己烷的制备.3 实验二、乙酰苯胺的制备.6 实验三、从茶叶中提取咖啡因.8 实验四、配合物键合异构体的制备及红外光谱测定.14 实验五、离子型化合物的离子交换分离.19 实验六、常见有机化合物的化学鉴别.21 实验七、乙酰二茂铁的制备与分离.22 2
实验一、溴代环已烷的制备SynthesisofbromocyclohaxanefromcyclohexenePreviewIn this reaction, we will beadding a concentrated HBr solutionto an alkenetoproduce an alkyl halide. This reaction proceeds by an acid-base reaction between thealkene and HBr to produce a carbocation, followed by an association reactionbetweenthe carbocation and bromide ion,Before comingtolab,pleaseread all of theprocedures given below.Write an introduction in your lab notebook.Fill out thefollowing table and include it in your introduction.HBrThen review the following techniaues."Refluxing a Reaction""Extraction and washing.MWreagentvolumedensitymassmmoleseq15mL1.0cyclohexenesoln:5ml.HBr48%1.490 g/mlHBr:xxbromocyclohexaneChemicalsCyclohexene, 48% HBrProcedureSet-up and run the reaction: Add the cyclohexene to a round-bottom flask using a graduatedpipette·Add theHBr solutiontothereaction usinga graduated cylinder.·Add a spin vane.3
实验一、溴代环己烷的制备 Synthesis of bromocyclohaxane from cyclohexene Preview In this reaction, we will be adding a concentrated HBr solution to an alkene to produce an alkyl halide. This reaction proceeds by an acid-base reaction between the alkene and HBr to produce a carbocation, followed by an association reaction between the carbocation and bromide ion. Before coming to lab, please read all of the procedures given below. Write an introduction in your lab notebook. Fill out the following table and include it in your introduction. Then review the following techniques: "Refluxing a Reaction," "Extraction and washing," "Drying and Organic Solvent," and "Evaporating an Organic Solvent. 1.5 mL 5 mL Chemicals Cyclohexene, 48% HBr Procedure Set-up and run the reaction: • Add the cyclohexene to a round-bottom flask using a graduated pipette. • Add the HBr solution to the reaction using a graduated cylinder. • Add a spin vane. 3
· Add a reflux condenser,clamping the condenser in place, and set up the tubing.. Turn on the water, then turn the stirring up until the two phases mix as much aspossible without causing the spin vane to just vibrate (it will help if you are careful tocenter the conical vial on the stirrer-hot plate).. Slowly heat the reaction until you can see it begin to reflux.. Heat at reflux for 1 hour (starting from the time you see it begin to reflux). (You areok as long as the bubbles don't get out of the top of the condenser.)Isolation oftheproduct:: Allow the reaction to cool. When it nears room temperature, remove it from thereflux condenser, and remove the spin vane with forceps. Cool the vial for a minute in an ice bath (don't put a hot vial in the ice bath or it willcrack!). You should be able to see a small layer of clear liquid on the top (density ofpure bromohexane: 1.349 g/cm') - this is the product, together with any unreactedcyclohexene.: Add some diethyl ether to dissolve the organic compounds - mix it up by drawing itin and out of a plastic pipette a few times - two layers should form.: With a pipette, carefully suck the aqueous layer (the bottom phase) out of the vialand into a separatory funnel (stopcock closed with beaker underneath). Set the vialcontaining the top layer aside where it won't get spilled.· Extract out any product that might remain in the water layer by adding several ml offresh ether to the separatory funnel and shaking carefully.Allow the layers to separate.Then drain off the water layer (bottom) into a beaker and set it aside for later disposal.· Now add the ether layer from the reaction to the separatory funnel, combining itwith the ether layer already there. This should contain the entire product.. Wash the ether layers to removing any remaining acid by adding a layer of saturatedNaHCOs to the ether solution. Add it slowly, as there will be a lot of bubbling as thebicarbonate reacts with the acid. When the bubbling dies down,put in the stopper andshake it carefully, venting frequently. Drain off the aqueous (bottom) layer· Add fresh bicarbonate solution and repeat.4
• Add a reflux condenser, clamping the condenser in place, and set up the tubing. • Turn on the water, then turn the stirring up until the two phases mix as much as possible without causing the spin vane to just vibrate (it will help if you are careful to center the conical vial on the stirrer-hot plate). • Slowly heat the reaction until you can see it begin to reflux. • Heat at reflux for 1 hour (starting from the time you see it begin to reflux). (You are ok as long as the bubbles don't get out of the top of the condenser.) Isolation of the product: • Allow the reaction to cool. When it nears room temperature, remove it from the reflux condenser, and remove the spin vane with forceps. • Cool the vial for a minute in an ice bath (don't put a hot vial in the ice bath or it will crack!). You should be able to see a small layer of clear liquid on the top (density of pure bromohexane: 1.349 g/cm3 ) – this is the product, together with any unreacted cyclohexene. • Add some diethyl ether to dissolve the organic compounds - mix it up by drawing it in and out of a plastic pipette a few times – two layers should form. • With a pipette, carefully suck the aqueous layer (the bottom phase) out of the vial and into a separatory funnel (stopcock closed with beaker underneath!). Set the vial containing the top layer aside where it won’t get spilled. • Extract out any product that might remain in the water layer by adding several ml of fresh ether to the separatory funnel and shaking carefully. Allow the layers to separate. Then drain off the water layer (bottom) into a beaker and set it aside for later disposal. • Now add the ether layer from the reaction to the separatory funnel, combining it with the ether layer already there. This should contain the entire product. • Wash the ether layers to removing any remaining acid by adding a layer of saturated NaHCO3 to the ether solution. Add it slowly, as there will be a lot of bubbling as the bicarbonate reacts with the acid. When the bubbling dies down, put in the stopper and shake it carefully, venting frequently. Drain off the aqueous (bottom) layer. • Add fresh bicarbonate solution and repeat. 4
·Drain the ether layer into a 50 ml beaker and dry the solution over sodium sulfate. Ifthe ether has evaporated so that you only have a small amount of solution, add moreether - if there is too little ether, it can be very hard to tell if it is free-flowing·Pour the dried ether solution into a clean,tared conical vial.Prepare a hot water bathin a small beaker at around 60°C. Evaporate the ether by setting the conical vial in thebath, with one end of your forceps inside to keep it from bumping. Don't fill it too fullor it may boil over. If you have too much to fit in the conical vial, add some, boil it off,then add somemore.When nomore bubbles form and thelevel of liquid doesn't seemto be going down, all of the solvent should be goneCharacterizetheproduct:. Note the appearance of your product, pure, authentic bromocyclohexane is a clear,colorless liquid.. Once it is cool, obtain its mass and calculate the % yield· Measure its refractive index and compare it with literature value (n 1.495)NotesConcentrated hydrogen bromide is corrosive and toxic; please do not remove from the fumehood, anduse care not to come in contact with thechemical.Questions(1) Draw the mechanism for this reaction. Is the addition regioselective in thiscase? Why or why not?(2) Why was it necessary to reflux this reaction?(3) Why did the reaction have two layers?(4) What is the purpose of extracting the water layer with ether?(5) What is the purpose of washing the ether layer with sodium bicarbonate?(6) Write the reaction that takes place when sodium bicarbonate reacts with HBr.What causes the bubbling?(7) What bands on the IR tell you if the product was formed? How would youknow if there was any starting material contaminating the product?5
• Drain the ether layer into a 50 ml beaker and dry the solution over sodium sulfate. If the ether has evaporated so that you only have a small amount of solution, add more ether – if there is too little ether, it can be very hard to tell if it is free-flowing. • Pour the dried ether solution into a clean, tared conical vial. Prepare a hot water bath in a small beaker at around 60o C. Evaporate the ether by setting the conical vial in the bath, with one end of your forceps inside to keep it from bumping. Don't fill it too full or it may boil over. If you have too much to fit in the conical vial, add some, boil it off, then add some more. When no more bubbles form and the level of liquid doesn't seem to be going down, all of the solvent should be gone. Characterize the product: • Note the appearance of your product; pure, authentic bromocyclohexane is a clear, colorless liquid. • Once it is cool, obtain its mass and calculate the % yield. • Measure its refractive index and compare it with literature value ( 1.495). Notes Concentrated hydrogen bromide is corrosive and toxic; please do not remove from the fume hood, and use care not to come in contact with the chemical. Questions (1) Draw the mechanism for this reaction. Is the addition regioselective in this case? Why or why not? (2) Why was it necessary to reflux this reaction? (3) Why did the reaction have two layers? (4) What is the purpose of extracting the water layer with ether? (5) What is the purpose of washing the ether layer with sodium bicarbonate? (6) Write the reaction that takes place when sodium bicarbonate reacts with HBr. What causes the bubbling? (7) What bands on the IR tell you if the product was formed? How would you know if there was any starting material contaminating the product? 5