精品课程上网材料之六
有机化学实验习题
（Experimental Organic Chemistry,
Experiment 2
Questions）
Determination of Melting Point
1. What would be the effect of each of the following conditions on a melting –point
determination?
a. presence of an insoluble impurity such as silica.
b. temperature raised too rapidly.
c. incomplete drying (i,e,incomplete removal of volatile solvent).
d. oil level in The tube below upper connection of side loop.
Experiment 3
Recrystallization
1. How many steps does the process of recrystallization be involved? What is the purpose of
each step?
2. Why should the amount of the solvent consumed in recrystallization be neither too much
nor too little? How to do it exactly?
3. Why should the amount of the solvent added in dissolving the rude product be less than
that by calculations? What is the purpose of adding the solvent bit by bit until the solid
exactly dissolves at the boiling point?
Experiment 4
Simple distillation
1. Why are boiling chips added into a heated liquid?
2. Why should the distillation apparatus have an opening to the atmosphere at the end ?
Experiment 5
Fractional distillation
1. What is an azeotropic mixture? Why cannot its components be separated by fractional
distillation?
2. Describe the characteristics of simple distillation and fractional distillation respectively.
Experiment 6
Steam distillation
1. Please describe the basic principle of steam distillation?
2. What are the functions of T-tube and safety column?
3. How do you judge that steam distillation is complete?
1
Experiment 7
Vacuum Distillation
1. Using the nomograph in Figure 2-, approximate the boiling points of the following substances
at atmospheric pressure (760mmHg).
(1) 1,6-hexanediol, bp.132℃ (10mmHg, 1.33KPa)
(2) ethyl, bp.101.4℃ (20mmHg, 2.60KPa)
2. Explain why a vacuum distillation apparatus should be checked for leaks before the material to
be distilled is placed in the flask.
Experiment 8
Solvent Extraction and Solution Washing
1. What will influence the efficiency of extraction and how to select proper solvent?
2. What is the purpose of using the separatory funnel and what should we need to pay attention
to itsusage ?
3. When two kinds of immiscible liquids are in the separatory funnel, which layer does the
material of larger gravity lie in? Where does the lower layer realease from? How to prevent
the liquid from flowing too quickly when drain it? How to deliver the liquid of the higher
layer into another container?
Experiment 9
Measurement the Refractive Index of Liquids
1. A compound has a refractive index of 1.3968at 17.5℃, calculate its refractive at 20.0℃.
2. It is usually recommended that the glass surfaces of a refractometer be cleaned with ethanol or
methanol, and not with acetone, what is the reason for this?
3. White a stepwise summary of using an Abbe refractome？
Experiment 10
Thin –Layer Chromatography(TLC)
1. Which of the two isomers of azobenzene would you expect to be the more thermodynamically
stable? Why?
2. In a TLC experiment why must be the spot not be immersed in the solvent in the developing
chamber?
3. Explain why the Rf of anti-azobenzene is greater than the Rf of syn-azobenzene.
3.16 Experiment 11
Isolation of Caffeine From Tea Leaves
1. Assume that your crude caffeine is nearly pure caffeine. How does the percentage yield of crude
caffeine obtained in this experiment compare with the expected value of 3% caffeine in tea
leaves? Is there a discrepancy between your result and the normal value? Give a feasible
explanation.
2. Try to make a comparison between microwave-assisted and soxhlet extraction and describe
their features.
2
Experiment 12
Synthesis of n-Butyl Bromide
1. Sulfuric acid plays several roles in the reactions, can you describe them
2. Di-butyl ether, 1-butene and 2-butene can be obtained as by-products in the reactions, explain
how to be removed by sulfuric acid in the form of equations.
3. Why must the crude n-butyl bromide be dried carefully with calcium chloride prior to the final
distillation?
4 .Why must the organic layer be washed with water before washing with 10% NaOH (to remove
trace acid) in the work-up procedure for n-butyl bromide?
Experiment 13
Synthesis of Triphenylmethanol
3
2
=
1. In the preparation of the Grignard reagent, anhydrous conditions must be remained during the
reaction. What will happen if water gets into the system?
2. Provide methods for preparing the following compounds by the Grignard method.
O
(1)
(2)
CH CH CHCH
3
CH3CH2CH2COH
OH
(3)
(4)
CHCH3
OH
Experiment 14
CH3
CH3CH2
C CH2CH3
OH
Synthesis of Dibutyl Ether
1. What accounts for the difference between the principles and procedures of preparations of
diethyl ether and dibutyl ether?
2. How do you strictly control the temperature of the reaction and how do you know the reaction
is nearly completed?
3. What is the purpose of each washing step?
Experiment 15
Synthesis of benzoic acid and benzyl alcohol
1. The Cannizzaro reaction occurs much more slowly in dilute sodium hydroxide solution than in
concentrated solution. Why?
2. By what means would aqueous sodium bisulfite remove unchanged benzaldehyde from the
reaction mixture?
Experiment 16
Synthesis of adipic acid
1. Why is it strongly required to control the temperature of oxidation reaction?
Experiment 17
Preparation Of Cinnamic Acid
1.What can we get from the reaction of benzaldehyde with propionic anhydride in the presence of
3
anhydrous potassium propionate?
Experiment 18
Synthesis of Acetylsalicylic Acid (Aspirin)
1. What is the purpose of the concentrated sulfuric acid used in the acetylation reactions?
2. What is the product when salicylic acid reacts with excess ethanol in the presence of the
concentrated sulfuric acid?
Experiment 19
Synthesis of Ethyl Acetate
1 What is the purpose of the use of sulfuric acid in this experiment?
2 What methods can be used to shift the equilibrium in the esterification in order to favor
products?
3 Which impurities may be contained in the crude ester, and how can they be removed?
Experiment 20
Synthesis of
n-Butyl Acetate
1. Why must all the glassware and reagents using in this experiment be dry and absolutely
anhydrous?
2. In the work up procedure for ethyl acetoacetate, what is the purpose of adding 50% acetic acid
and saturated NaCl?
Experiment 21
Synthesis of Ethyl Acetoacetate
1. Why must all the glassware and reagents using in this experiment be dry and absolutely
anhydrous?
2. In the work up procedure for ethyl acetoacetate, what is the purpose of adding 50% acetic acid
and saturated NaCl?
Experiment 22
Synthesis of Acetanilide
1. In method one, why must the temperature of the distilling vapor be controlled to about 105℃?
2．In method two, why must sodium acetate be added immediately after the acetic anhydride is
dissolved? What is the function of sodium acetate?
3. Why is the ice-cold water rather than room temperature water used to wash the final product?
Experiment 23
Synthesis of p-Acetylaminobenzenesulfonyl Chloride
1. Why is chlorosulfonic acid a dangerous reagent when it comes in contact with water?
2. In the procedure of step 6, why must the reaction mixture be poured slowly onto the ice with
constant stirring?
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Experiment 24
Synthesis of p-aminobenzenesulfonamide (Sulfanilamide)
1. In the preparation of sulfanilamide from p-acetylaminobenzenesulfonyl chloride, is only the
acetamide group hydrolyzed? Give an explanation for the difference in reactivity of acetamide
and sulfonamide groups.
2. Assume that in the process of the converting the ammonium salt to the amine (the procedure 2),
you brought the pH only to 6 instead of 8, how would that effect you yield?
Experiment 25
Synthesis of
2-Furanmethanol and
2-Furoic acid
1. In this experiment, why the newly-distillated furfuraldehyde should be used?
2. Why the reaction solution should be extracted with ether four times? What product is to be
extracted？
Experiment 26
Synthesis of Methyl Orange
1. In this experiment, why the temperature of procedure 4 should be controlled below 5℃?
2. Why does the dimethylaniline coupling with diazonium salt at the paraposition of the ring?
3. What would be the result if cuprous chloride were added to the diazonium salt prepared in this
reaction?
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