Sunday, June 14, 2009

Chem.070 Lab.Assignments and Review Sheets

LATTC Dr.DARMANYAN
Chem70
Lab Report Outline

Page 1 (3 pts)

• Student’s Name, class, date, #
• Objectives
• Assignment
• Materials
• Chemicals
• Safety precautions
• Apparatus with specification of the parts.


Page 2 (7 pts)
Procedure and Observations

No Step Observation


Do not copy the entire procedure.
For each step use 1-2 sentences (main points)

Page 3 (5 pts)
Table of Results


No Step Result/Equation



• Give the title to the table.
• If necessary, make two or more tables
• In the “Step” column, indicate only the name of step taken
• In the Result/Equation column, use 1-2 sentences to formulate the result of the step.
• For the chemical reaction that occurs, write down the equation.

Page 4 (5 pts)
• Discussion
Discuss the results of the experiment, trends, regularities, relationships, etc

• Conclusion
Make conclusion about what you have learned from this lab.



LATTC
Chemistry 70 Dr.Darmanyan

Lab. # 1: HYDROCARBONS I
(Saturated HC)


Assignment:
1. Investigate physical and chemical properties of alkanes
2. Discuss how physical and chemical properties of alkanes depend on their structure


Materials: Porcelain evaporating dishes, tongs, test tubes, test tube holder, test tube rack, Bunsen burner, 10-mL graduated cylinder, plastic droppers


Chemicals: Alkane (pentane), bromine solution, potassium permanganate solution, conc. sulfuric acid

Safety precautions:1. Wear safety goggles!
2. Hydrocarbons are extremely flammable and should not be handled near open flames. Avoid inhaling the vapor, contact with skin and closing, and do not ingest.
3. Concentrated sulfuric acid is very dangerous. Follow the safety rules and instructor’s recommendations.
4. Dispense bromine solution under the hood, and be especially careful not to spill bromine on your hands.


Procedure:

Part I. Physical Properties of Alkanes
1. Observing physical properties of alkanes
Observe the following physical properties of alkanes: state of matter, color, odor.
2. Interaction with water
A. Solubility Test
Test the solubility of alkanes in water by adding 10 drops (about 0.4 mL) of tested hydrocarbon to about 2 mL portions of water in a test tube. Shake each mixture for a few seconds and note whether they are soluble.

B. Relative density
Note the relative density of the alkane with respect to water.

Part II. Chemical Properties of Alkanes
2.I. Substitution reactions
A. Bromination
Take a clean dry test tube. Place 20 drops of alkane in test tube and add 1 drop of bromine solution. Stopper the tube and note for 1 min how fast (fast, slow, or no disappearance) the color disappears.
Take another clean dry test tube. Repeat the above procedure. After 1 min, expose the test tube to a strong electric light for an additional 2 min. Note the color change.

B. Sulfonation

Take a clean dry test tube. Place 10 drops of concentrated sulfuric acid in test tube and add 20 drops of alkane. Shake the test tube by gently striding the bottom of the tube. Note is the hydrocarbon dissolves or there is a color change.


2.2. Oxidation
A. Reaction with potassium permanganate

Place 20 drops of alkane in the test tube. Add 4 drops of potassium permanganate solution and note how the color changes.

B. Combustion
1) Combustion of gaseous alkanes
Use Bunsen burner under for combustion of natural gas (methane or propane). Note the characteristic of the flame.

2) Combustion of liquid alkane
Place 5 drops of liquid alkane in an evaporating dish and start it burning by carefully bringing a lighted splint to it. Note the characteristics of the flame.



Lab # 2: HYDROCARBONS II
(Unsaturated and Aromatic HC)


Assignment:
1. Investigate physical and chemical properties of unsaturated and aromatic HC
2. Discuss how physical and chemical properties of HC depend on their structure
3.Compare and contrast chemical properties of alkanes, alkenes, and aromatic HC


Materials: Porcelain evaporating dishes, tongs, test tubes, test tube holder, test tube rack, 10-mL graduated cylinder, plastic droppers

Chemicals: Alkene (cyclohexene), aromatic HC (benzene), bromine solution, potassium permanganate solution, conc. sulfuric acid, calcium carbide

Safety precautions:
1. Wear safety goggles!
2. Hydrocarbons are extremely flammable and should not be handled near open flames. Avoid inhaling the vapor, contact with skin and closing, and do not ingest.
3. Concentrated sulfuric acid is very dangerous. Follow the safety rules and instructor’s recommendations.
4. Dispense bromine solution under the hood, and be especially careful not to spill bromine on your hands.


Procedure:

Part I. Physical Properties of Alkenes and Aromatic HC

1. Observing physical properties of hydrocarbons
Observe the following physical properties of HC: state of matter, color, odor.

2. Interaction with water
A. Solubility Test
Test the solubility of HC (cyclohexene and benzene) in water by adding 10 drops (about 0.4 mL)of tested hydrocarbon to about 2 mL portions of water in a test tube. Shake each mixture for a few seconds and note whether they are soluble.

B. Relative density
Note the relative density of tested HC with respect to water.

C. Miscibility
Test the miscibility of two hydrocarbons with each other by mixing 10 drops of alkene (cyclohexene) with 10 drops of aromatic HC (benzeneene) in dry test tube.

Part II. Chemical Properties of Alkenes and Aromatic HC

2.I. Addition reactions of alkenes
A. Bromination (test for the presence of double bond)
Take a clean dry test tube. Place 20 drops of alkene in test tube and add 1 drop of bromine solution. Stopper the tube and note for 1 min how fast (fast, slow, or no disappearance) the color disappears.

B. Sulfonation

Take a clean dry test tube. Place 10 drops of concentrated sulfuric acid in test tube and add 20 drops of alkene. Shake the test tube by gently striding the bottom of the tube. Note is the hydrocarbon dissolves or there is a color change.

2.2 Substitution reactions of aromatic HC
A. Bromination
Place 20 drops of benzene in test tube and add 1 drop of bromine solution. Stopper the tube and note for 1 min how fast (fast, slow, or no disappearance) the color disappears.

B. Sulfonation
Place 10 drops of concentrated sulfuric acid in test tube and add 20 drops of benzene. Shake the test tube by gently striding the bottom of the tube. Note is the hydrocarbon dissolves or there is a color change.

2.3. Oxidation of alkenes and aromatic HC
A. Reaction with potassium permanganate (The Baeyer’s test for double bond presence)

Place 20 drops of alkene in one test tube and 20 drops of benzene in another test tube. Add 4 drops of potassium permanganate solution in each test tube and note how the color changes.

B. Combustion
Place 5 drops of alkene in one evaporating dish and 5 drops of benzene in another evaporating dish. Start it burning by carefully bringing a lighted splint to it. Note the characteristics of the flame.


2.4. Preparation and properties of acetylene (This will be done as a demonstration by your instructor)
A. Preparation of acetylene
Acetylene can easily be obtained by the reaction of calcium carbide with water as follows:
CaC2 + 2H2O = Ca(OH)2 + HC=CH
C. Physical properties of acetylene
Observe the state of matter, color, and odor of acetylene
D. Chemical properties of acetylene
1) Addition reaction (bromination): Note the color change
2) Oxidation reaction (with potassium permanganate): Note the color change
3) Combustion: Note the characteristics of the flame


Lab # 3: FUNCTIONAL GROUPS I
(Hydroxyl group
)
Assignment:
1. Investigate chemical properties of alcohols and phenols.
2. Compare primary, secondary, and tertiary alcohols and state the relationship between their structure and chemical activity
3. Compare alcohols and phenols, and state the relationship between their structure and chemical activity.

Materials: Test tubes, beaker 400 mL, plastic droppers, hot plate, thermometer

Chemicals: Alcohols (1-butanol, 2-butanol, t-butanol), phenol ,acetone, Lucas reagent, chromic anhydride,
10% solution of NaOH, bromine solution

Safety precautions: Wear safety goggles!

Procedure:

1. Substitution reactions
1.1. Substitution of hydroxyl group (Lucas Test - comparing primary, secondary,
and tertiary alcohols)

Take 3 clean and dry test tubes. Place 25 drops (about 1.0 mL)of the prepared Lucas reagent (anhydrous zinc chloride dissolved in concentrated hydrochloric acid) in each test tube. Add 5 drops of tested alcohol and shake briefly. As the reaction occurs, a clear solution become cloudy because the chloride formed is not soluble in the reagent. Wait several minutes and then put the test tubes with no reaction into a beaker of water of 60oC. The tertiary alcohol should react at room temperature, the secondary alcohol at 60oC, and the primary alcohol won’t react unless heated for some time
Tested compounds: 1-butanol, 2-butanol, t-butanol

1.2. Substitution of hydrogen in hydroxyl group (Reaction of alcohol and phenol
with sodium hydroxide)

A. Reaction with alcohol
Place 20 drops of an alcohol (1-butanol) in the test tube. Add 20 drops of 10% solution of NaOH. Note any change.

b. Reaction with phenol
Place 20 drops of water in the test tube. Add 10 drops of phenol. Describe the mixture. Then add 30 drops of 10% solution of NaOH. Note any change.

1.3. Substitution of hydrogen in carbon chain of alcohols and phenols
(Bromination reaction)

Place 20 drops of an alcohol (1-butanol) in the test tube. Add 2 drops of bromine solution. Note any change.
Place 20 drops of water and 10 drops of phenol in another test tube. Add 3 drops of bromine solution to the mixture. Note any change.

2. Oxidation reaction of alcohols (comparing primary, secondary, and tertiary alcohols)
Take 3 clean and dry test tubes. Place 25 drops of acetone to each test tube. Add 2 drops of the tested alcohol and then add an equal amount of chromic acid reagent. The yellow color should change immediately to the greenish blue of the chromic ion. If the solution remains yellow for 2 sec, the test is negative. Be sure to do a blank on the acetone (with no alcohol added).
Tested compounds: 1-butanol, 2-butanol, t-butanol

Lab # 4: FUNCTIONAL GROUPS II
(Carbonyl group)

Assignment:
1. Investigate chemical properties of aldehydes and ketones
2. Compare aldehydes and ketons, and state the relationship between their structure and chemical activity.


Materials: Test tubes, beaker 400 mL, plastic droppers, hot plate, thermometer.

Chemicals: 2,4-dinitrophenylhydrazine (2,4-DNP), cinnamaldehyde (3-phenylpropanal), 1% glucose solution, acetone, 3-pentanone

Safety precautions: Wear safety goggles!
Be careful with 2,4-DNP reagent. It stains!


Procedure:

I. Addition reaction (Qualitative test on carbonyl group with 2.4-DNP)
Place 20 drops of the 2,4-DNP reagent (2,4-Dinitrophenylhydrazine in sulfuric acid) in a test tube (be careful, it stains!). Add 3 drops of tested compound and shake carefully.
Make a conclusion about presence of the carbonyl group.
Tested compounds: acetone, cinnamaldehyde (3-phenylpropenal), 3-pentanone


2. Oxidation reactions
2.1.Fehling’s test (presence of aldehyde group)
Take 25 drops of Fehling’s A and 20 drops of Fheling’s B solutions and mix them.
Place 3 drops of the compounds to be tested to each tube and place the tubes in the
warm-water bath. Also, place one tube in the bath that has only the reagent init for a blank. Examine for any change in color or for a red precipitate on the bottom of the tube.
Tested compounds: acetone and glucose

2.2. Tollens’ test (presence of aldehyde group)
Place 20 drops of 0.1 M silver nitrate solution into a test tube. Add 6 M dilute ammonia dropwise until the brown precipitate that forms at first almost redissolves. Shake the tube between each drop so that you do not add too much ammonia.
Place 25 drops1 of prepared solution in a test tube and add 2 drops of the compound to be tested.
You may warm it gently, but be careful as you may just decompose the reagent. You may test this by warming a sample of the reagent alone with an aldehyde, you will observe a fine black precipitate, or if you are lucky and the tube is clean, you may observe silver the inside of the tube, giving a mirror that you can see from the outside.
Tested compounds: acetone and glucose

2.3. Benedict’s test (presence of aldehyde group)
Place 20 drops of a 1% tested compound and 20 drops of Benedict’s solution in a test tube.
Prepare a control using 20 drops of distilled water instead of glucose. Place the two tubes in a boiling water bath for 2-3 min. Observe the color of the solution and note whether a precipitate has formed.
The formation of an insoluble copper (I) oxide precipitate serves as a criterion of a positive reaction indicating the presence of aldehyde group. The color of the precipitate can vary from green to yellow to brick red because of the varying sizes of the precipitatied particles and their differing absorption of visible light.

Tested compounds: 1% solution of glucose, cynnamaldehyde, acetone.


Lab. # 5 :FUNCTIONAL GROUPS III
(carboxyl group)


Assignment:
1. Investigate chemical properties of carboxylic acids.
2. Compare acidic properties of alcohols, phenols, and acids.


Materials: Test tubes, beaker 400 mL, plastic droppers, hot plate.

Chemicals: Acetic acid, benzoic acid, salicylic acid, 10% NaOH solution, 6 N HCl solution, NaHCO3 solution, methanol, 1-propanol, propanoic acid, conc. H2SO4, bromine solution

Safety precautions: Wear safety goggles!

Procedure:

1. Acidic properties

1.1. Dissociation reaction
Place 1 drop of acetic acid on pH paper. Record the pH value.

1.2. Neutralization reaction

A. With acetic acid
Place 20 drops of 10% of NaOH solution in the test tube. Add 1 drop of indicator phenolphthalein.
Add a few drops of acetic acid until solution becomes colorless.

B. With benzoic acid
Place 35 drops of water in a test tube. Add ~ 0.1 g of benzoic acid. Observe the solubility of benzoic acid in water.
Place about half of the test tube content into another test tube and add 10% of sodium hydroxide solution dropwise until the acid dissolves.
Place about half of this test tube content into another test tube and add
Add 6 N hydrochloric acid dropwise to recover benzoic acid.

1.3. Reaction with sodium hydrogen carbonate, NaHCO3
Place 20 drops of 10% of NaHCO3 solution in the test tube. Add 1 drop of indicator phenolphthalein. Add a 20 drops of acetic acid. Note any change.

2. Substitution reaction (esterification)

2.1. Synthesis of propyl propanoate
Place 25 drops each of 1-propanol (note odor) and propanoic acid (note odor carefully) in a test tube.
Add 3 drops of concentrated sulfuric acid, and place the test tube in a hot-water bath. After 15 or more minutes, add 2 to 3 mL of ice water. Observe an oily layer separated. Note the odor.

2.2. Oil of Wintergreen
Fill a 10 x 75 mm test tube to a height of about 1.5 cm with salicylic acid. Add about 5 mL of methanol and about 1 mL of concentrated sulfuric acid. Heat in a boiling-water bath for 5 to 10 min. Pour into asmall beaker containing about 20 mL of crushed ice. Check the fragrance.



Lab # 6: CRYSTALLIZATION

Assignment:
1. Use crystallization method to purify benzoic acid
2. Find out a percent yield by using the following formula:

Mass of dried purified product
% Yield = ------------------------------------------ x 100%
Mass of the crude product

3. Save your product for the next lab.
4. Answer the discussion questions:
a. Where will be the impurities after you complete your experiment?
b. Explain why you result (% Yield) is below 100%.

Introduction
Crystallization is a method of purification of organic compounds that are solid at room temperature. The general technique involves dissolving the material to be crystallized in a hot solvent and cooling the solution slowly.
For the successful purification, the two requirements should be met:
1. Choose an appropriate solvent
Ideally, the appropriate solvent is the one in which the material to be crystallized is sparingly soluble at room temperature and yet quite soluble at the boiling point of solvent selected. A successful crystallization depends on large difference in the solubility of a material in a hot solvent and its solubility in the same solvent cold. A material can be purified by crystallization when both the desired substance and the impurities have similar solubility, but the desired substance will crystallize on cooling while the impurities will not. Also, the proper solvent should not react with the solid substance.

2. Cool down the solution slowly
To produce a very pure material, too rapid process should be avoided. Too slow process should also be avoided. The time scale for crystal formation should cover tens of minutes or hours, rather than seconds or days.

Procedure

1. Weigh about 0.50 g (0.48-0.52 g) of crude product (benzoic acid). Record your measurement to 0.01 g.
2. Place your sample into a 50-mL Erlenmeyer flask.
3. Add a minimal amount (about 2 mL) of the hot solvent (water).
4. Place the flask on hot plate and cover it with a watch glass with ice on top to prevent water to evaporate from the flask.
5. Heat the flask slowly until water starts to boil, then turn off the hot plate and let the crystals dissolve.
6. If undissolved solid still present, then slowly (0.5 mL at a time) add more hot solvent until all the product dissolves. Take care not to leave any traces of slid in the flask.
7. Set the solution aside and allow the flask to cool slowly to room temperature until crystals are formed.
8. Transfer the crystals from the flask on a Hirsh funnel. Use a small amount of ice-cold water if needed.
9. Using vacuum filtration on a Hirsch funnel, collect the crystals.
10. Rinse the crystals with a small amount of ice-cold original solvent.
11. Put the crystals on the watch glass for drying at the temperature between
60-70oC.
12. Measure the mass of the dried purified product.


Lab # 7A: MELTING POINT

Assignment:

1. Determine the melting point of your product (dried purified benzoic acid)
2. Compare you experimental value with a true value of the melting point of your substance.
t fus theor - t fus exp.
% error = -------------------------- x 100%
t fus theor

3. Explain the possible sources of the error.

Introduction
The melting point of a pure crystalline substance is a physical property of that substance. This melting point can be used to identify a given substance as well as check the level of its purity.
A small amount of material is heated slowly in a special apparatus equipped with a thermometer, a heating coil (or a heating bath), and usually a magnifying eyepiece for observing the sample. Two temperatures are noted. The first is the point at which the first drop of liquid forms among crystals; the second is the point at which the whole mass of crystals turns to a clear liquid. The melting point is then recorded, giving this range of melting. For example, if you say that melting point is 51 to 54oC, that is the substance melted over a 3o range.

Procedure
Packing the melting-point tube
Melting point usually is determined by heating the sample in a piece
of thin-walled capillary tubing (1mm x 100 mm) that has been sealed
at one end. To pack the tube:
1. Press the open end gently into a pulverized sample of the
crystalline material. Crystals will stick in the open end of the tube.
The amount of solid pressed into the tube should correspond to
a column of about 1 mm high.
2. To transfer the crystals to the closed end of the tube, drop the
capillary, closed end first, down a 2/3-m length of glass tubing,
which is held upright on the desk top. The crystals will pack down
into the bottom of the tube.
3. Repeat the procedure if necessary. Tapping the capillary on the
desk top with the fingers is not recommended.

Determining the melting point1.
The electrical apparatus (heat and thermometer) is used to determine the melting point. The capillary tube is inserted in apparatus. Make a sketch of this apparatus in your lab report.
2. If the melting point is unknown, the approximate melting point can be determined by rapid heating of the sample. The capillary tube is disposed in an appropriate receptacle.
3. For accurate determination of the melting point, the second sample can be heated rapidly to about 20oC below the approximate melting point observed in step. Then the heating rate is reduced to 1-2oC/min. The range of the melting process and other observations are noted in the lab notebook.
4. The melting-point apparatus is turned off and the melting point capillary is disposed in he glass trash.


Lab # 7B: Boiling point:

Assignment:
1. Determine the boiling point of unknown liquid.
2. Identify the unknown liquid (its name) by comparing your experimental
value with the true value (assigned by the instructor) and calculate the percent error.
3. Analyze the possible sources of error
4. By using the chart of boiling point values of different liquids used in the lab, state the effect of the structure of liquids on their boiling points:
- the type of carbon skeleton (straight, branched, etc)
- the length of carbon chain
- the type of functional group (hydroxyl, aldehyde, keto)

Introduction
The boiling point is a temperature at which the vapor pressure of the liquid equals the applied pressure (usually atmospheric pressure). At this point, the liquid will be observed to boil, and both liquid and vapor are at equilibrium. The normal boiling point is measured at 760 mm Hg (1 atmosphere). At a lower applied pressure, the vapor pressure needed for boiling is also lowered, and the liquid boils at a lower temperature.
Boiling point is used as a physical characteristic of a liquid to identify an unknown substance, as well as to determine the level of its purity. The presence of impurities lowers the boiling point of the substance.

Procedure
1. Set up an apparatus without thermometer (see the picture).
2. Place about 2-3 mL of the unknown liquid (assigned by the instructor) in a flask.
3. Add one piece boiling stone to the liquid, and attach the thermometer.
4. Heat up the water in a beaker (do not allow water to boil!).
5. Do not allow the liquid in the flask to evaporate completely during the process.
6. As the temperature does no longer increases, and range fluctuates only + 1.0oC, record the temperature as the boiling point.

Lab. #8: THIN-LAYER CHROMATOGRAPHY

Assignment:
1. Separate the mixture of dyes by TCL.
2. Indicate the number of components in the mixture and determine Rf for each component.
3. Identify each of them (find the name) by comparing Rf value for individual dyes (model) with Rf of the components of the mixture.
4. Identify the unknown sample (one dye or mixture of two dyes) and name it (them) by comparing the value of Rf for models) with Rf of your unknown.

Introduction
Chromatography in its various forms is perhaps the most important known method for the chemical analysis of mixtures. The more modern technique of thin-layer chromatography (TCL)uses a thin coating of aluminum oxide or silicagel on a glass microscope slide or plastic sheet, to which the mixture to be resolved is applied. The TCL slide coating used in chromatography is not inert, but consists of molecules that may interact with the molecules of the components of the mixture being separated. The coating of the TCL slide adsorbs molecules on its surface to differing extents, depending on the structure and properties of the molecules involved.
To place a TLC separation on a quantitative bases. A mathematical function called the retention factor, Rf, is defined:

Distance traveled by spot d(c)
Rf = ---------------------------------------- = -------
Distance traveled by solvent d(s)

In this experiment, you will perform a thin-layer chromatographic analysis of a mixture of the dyes bromcresol green, methyl red, and xylenol orange. These dyes have been chosen because they have significantly different retention factors, Rf, and a nearly complete separation should be possible in the appropriate solvent system. You will also investigate the effect of the solvent on TLC analyses
by attempting the separation in several different solvent systems. Finally, by using TCL, you will be able to identify an unknown dye.

Materials:
Bakerflex plastic TLC slides, latex surgical gloves, ruler, pencil. Plastic wrap or Parafilm, micropipets, hotplate, heat gun.

Chemicals:
Ethanolic solutions of the indicator dyes (methyl red, xylenol orange, bromcresol green), solvent (50% acetone/50% ehtylathetate).

Safety precautions:
Wear safety glasses at all times while in the laboratory.
• The organic indicator dyes used in this experiment will stain skin and clothing if spilled. Many such dyes are toxic or mutagenic.
• The solvent used for the chromatographic separation is highly flammable and its vapors are toxic. No flames should be burning in the room while the solvent is in use. Use the solvent only in the exhaust hood.

Procedure

Part I. Separation
1. Place 10 mL of the solvent into a jar, screw a cap, and measure height of the liquid.
2. Draw the staring line on the absorbent part of the plate 1.0 cm above the solvent height.
3. Draw the ending line 1.0 cm below top of the plate.
4. Using capillary, apply a single small droplet of the mixture to its pencil starting spot. Also, apply one droplet of each dye to their labeled spots.
5. Dry out spots for no longer than 5 min.
6. Place a plate into the jar and screw a cap.
7. As the solvent reaches the ending line, take the plate out and dry it out for 5 min.
8. Enclose each spot, mark the center of the spot and measure d(c) and d(s) Record your measurement in Date Table.
9. Calculate Rf and record it in Table of Result.

Part II. Identification
1. Prepare another slide as it is described in steps 1-3.
2. Repeat the procedure (steps 4) using your unknown instead of the mixture.
3. Follow the steps 5-9 to identify your unknown.
4. Attach the slide to your lab report.

Lab. # 9: CARBOHYDRATES I (Monosaccharides)

Assignment:
1. Investigate the chemical properties of monosaccharides (MS).
2. State the purpose of each test.
3. Compare the chemical properties of aldoses and ketoses.

Introduction
The chemical tests employed to detect carbohydrates and to distinguish among them.

Tests based on the production of furfural or a substituted furfural
(Molisch Test, Bial’s Test, Seliwanoff’s Test)

When a monosaccharide is treated with a concentrated acid solution, dehydration of the monosaccharide occurs. If the monosaccharide is a pentose, the dehydrated product is furfural; dehydration of a hexose yields hydroxymethylfurfural.
In presence of acid, various phenolic compounds (see below) will react with the furfural or hydroxymethylfurfural to form colored condensation products. The formation of these colored compounds constitutes a positive test for carbohydrates.

Tests based on the reducing property of carbohydrates
(Benedict’s Test, Barfoed’s Test)

Monosaccharides and those disaccharides possessing a potential aldehyde group (reducing sugars) will reduce certain oxidizing reagents such as cupric ion (as a complex with citrate ion – Benedict’s solution; as a complex with tartrate ion – Fehling’s solution), dinitrosalicylic acid, and picric acid. The amount of sugar present can be roughly estimated from the amount of precipitate and the color formed.
_
Materials:
10 mL graduated cylinder, 400 mL beaker, droppers, test tubes, hot plate.

Chemicals:

Tested carbohydrates: 1% solution of each: xylose, arabinose, glucose, fructose
Reagents: Molisch, Bial’s, Seliwanoff’s, Benedict’s, and Barfoed’s.

Solutions: concentrated sulfuric acid.

Safety Rules:
Wear safety goggles!

Procedure:
I. Molisch Test

The Molisch test is the most general test for carbohydrates. Compounds that are dehydrated by concentrated sulfuric acid to form furfural or hydroxymethylfurfural will react with alpha-naphthol to yield a purple condensation product. A negative result is a good evidence of the absence of carbohydrates.

1. Mix 12 drops of distilled water and 1 drop of the Molisch reagent in a test tube. This tube will serve as the control.

2. Place 12 drops of a 1% arabinose solution in a second test tube. Add 1 drop of the Molisch reagent, and mix the contents by gently shaking the test tube.

3. Incline the tube and cautiously add 25 drops (about 1 mL) of concentrated sulfuric acid, allowing the acid slowly to run down the side of the tube. Sulfuric acid has a greater density than water and thus it will form a layer under the arabinose solution. Note the color of the ring formed at the juncture of the two liquids.

4. In the same manner add sulfuric acid to the control tube. What do you observe?

5. Repeat the above test with 1% samples of other tested carbohydrates.

II. Bial’s Test

Bials’s test is important in the determination of pentoses and nucleotides that contain pentose sugars. It is based on the observation that furfural, which is formed from pentoses, yields a blue-green compound when treated with orcinol in the presence of ferric ions. Hydroxymethylfurfural, formed from hexoses, reacts with orcinol to give a yellow-brown condensation product. Therefore, observation of the color produced after addition of the test reagent allows one to distinguish pentoses from hexoses.

1. Place 12 drops of a 1% arabinose solution in a clean test tube.

2. Prepare a control test tube with 12 drops of distilled water.

3. To each tube add 15 drops of Bial’s reagent.

4. Carefully heat each tube over a Bunsen flame until the solution just begins to boil.

5. Note the color of the product formed in the sample tube.

6. Repeat the above test with 1% samples of glucose.


III. Seliwanoff’s Test

The dehydration of ketohexoses with hot hydrochloric acid occurs much faster than the dehydration of the corresponding aldohexoses. During the same time interval in which the dehydrated ketohexose reacts with resorcinol to form a bright red condensation product, the aldohexose yields only a pale pink coloration. Seliwanoff’s test, therefore, is essentially a test based upon differential rates of reaction. Prolonged heating of samples should be avoided. This test is useful for distinguishing fructose (a ketohexose) from glucose or any other aldohexose.

1. Place in separate labeled test tubes 12 drops each of three tested carbohydrate solutions (arabinose, glucose, fructose).

2. Prepare a control tube with 12 drops of distilled water.

3. To each test tube add 25 drops (about 1 mL) of Seliwanoff’s reagent.

4. Place the tubes in a beaker of boiling water for exactly 60 sec.

5. Note and record which sample tube gives the test in the shortest time.

6. Continue heating and observe the color change at 1 min intervals for 5 min.


IV. Benedict’s Test

The formation of an insoluble cuprous oxide precipitate serves as a criterion of a positive reaction indicating the presence of aldehyde group. The color of the precipitate can vary from green to yellow to brick red because of the varying sizes of the precipitatied particles and their differing absorption of visible light.

1. Place 12 drops of a 1% glucose solution and 15 drops of Benedict’s solution in a test tube.

2. Prepare a control using 20 drops of distilled water instead of glucose.

3. Place the two tubes in a boiling water bath for 2-3 min.

4. Observe the color of the solution and note whether a precipitate has formed.

5. Repeat the above test with 1% samples of fructose.



Lab # 10: CARBOHYDRATES II (Di- and Polysaccharides)

(Di- and Polysaccharides)

Assignment:

1. Investigate the chemical properties of di- and polysaccharides.
2. State the purpose of each test.
3. Compare chemical properties of reducing and nonreducing disaccharides.
4. Identify the unknown carbohydrate (either MS or DS) and name it.

Materials:
10 mL graduated cylinder, 400 mL beaker, droppers, test tubes, hot plate.

Chemicals:
Tested carbohydrates:
1% solution of each: arabinose, glucose, fructose, sucrose, maltose, starch.

Reagents: Molisch, Bial’s, Seliwanoff’s, Benedict’s, and Barfoed’s, red litmus paper

Solutions: 10% NaOH , conc. sulfuric acid, conc. hydrochloric acid, diluted iodine solution

Safety Rules:
Wear safety goggles!

Procedure:

I. Barfoed’s Test
The Barfoed’s Test is used to distinguish between reducing monosaccharides and disaccharides. This test differs from Benedict’s test in that the oxidation-reduction reaction is carried out in an acidic rather than a basic solution. Within the same time interval (10 min), only monosaccharides will reduce the cupric ion in the reagent. If heating is prolonged, the disaccharides may be hydrolyzed by the acid and the resulting monosaccharides will give a positive test.

1. Place 12 drops of a 1% glucose solution in a test tube # 1, 12 drops of a 1% maltose solution in a test tube # 2,and 12 drops of distilled water (a control) in a test tube # 3.

2. Add 1 mL of Barfoed’s reagent in each test tube.

3. Place the tubes in a boiling water bath for 10 min. Record your observations.

II. Hydrolysis of Sucrose
1. Mix together 3 mL of sucrose solution and 2 drops of concentrated hydrochloric acid.
2. Place the test tube in a beaker of boiling water for about 10 min.

3. Cool the solution and neutralize the acid with 10% NaOH solution (requires 5-7 drops of base). Use red litmus paper as an indicator.

4. Place 12 drops sample of the hydrolyzed sugar solution in a test tube # 1, and another 12 drops of the sample solution in a test tube # 2.

5. Use the solution in the test tube # 1 to run Benedict’s test (add 15 drops of the test reagent), and the solution in the test tube # 2 to run Seliwanoff test (add 25 drops of the test reagent).

6. As control experiment, use sucrose solution and mix it with Benedict’s and Seliwanoff’s reagent separately. Do not heat the solutions up.

III. Reducing properties of disaccharides
1. Place 12 drops sample of the maltose solution in a test tube # 1, and 12 drops of the sample of sucrose solution in a test tube # 2.

2. Add 15 drops (about 1 mL) of Benedict’s reagent in each test tube.

3. Place the two tubes in a boiling water bath for 2-3 min.

IV. Hydrolysis of Starch
1. Place about 250 mL of water into 400-ml beaker and heat it to gentle boiling (water bath).

2. Place about 5 mL of the starch solution into the test tube labeled #1.

3. Take about 1 mL of the starch solution from the test tube #1 and place it into test tube #2.

4. Add 1 drop of dilute iodine solution to the test tube #2 to test the starch solution before the hydrolysis.

5. Add 3 drops of concentrated HCl to the starch solution in the test tube #1.

6. Place the test tube #1 into 400-mL beaker with boiling water (water bath) for
10 min.

7. Take about 1 mL of the solution from the test tube #1 and place it into the test tube #3.

8. Return the test tube #1 back into 400-mL beaker with boiling water and let it stay in water bath for additional 10 min.

9. Cool the test tube #3 solution down to room temperature and add 1 drop of dilute iodine solution to test the starch after 10 min of hydrolysis.

10.After heating the test tube #1 solution for additional 10 min, take it out from the water bath and cool it down to room temperature.

11. Take about 1 mL of the solution from the test tube #1 and place it into the test tube #4.

12. Add 1 drop of dilute iodine solution to the test tube #4 to test the starch solution after 20 min of hydrolysis.

13. Neutralize the acid in the test tube #1 with 10 drops of 10% NaOH (check the end point of neutralization with red litmus paper).

14. Take 12 drops of the solution from the test tube #1 and run Benedict’s test (add 15 drops of the test reagent) to check the presens of maltose or glucose.

II. A Carbohydrate Unknown

Obtain an unknown carbohydrate from your laboratory instructor. Using the carbohydrate tests, determine which carbohydrate you have been given. The unknown will contain one of the carbohydrates tested, but polysaccharides will not be included. Use the following scheme of analysis by means of which various possible carbohydrates may be eliminated.
For each test use 12 drops of your unknown solution.


Lab.# 11: LIPIDS

Assignment:
1. Investigate the physical and chemical properties of lipids.
2. Prepare soap and investigate its physical and chemical properities.

Objective:
To learn and compare physical and chemical properties of different types of lipids.

Materials:
10 mL graduated cylinder, test tubes, 400 mL beaker, 50 mL beaker, 50 mL flask,
glass rod, plastic droppers

Chemicals:
Solids: cholesterol, coconut oil, stearic acid
Liquids: glycerol, vegetable oil, oleic acid, acetone, hexane
Solutions: 5% bromine in carbontetrachloride, NaOH pellets, 0.1 M HCl, 0.1 M NaOH, 5% MgCl2, 5% CaCl2
Indicators: pH paper

Safety rules:
Wear safety goggles

Procedure:
1. Solubility
Place about 0.1 g of cholesterol in test tube #1, 12 drops (about 0.5 ml) of glycerol in # 2, 12 drops of oleic acid in # 3, 12 drops of vegetable oil in # 4. Add 2 mL of water in each test tube and shake. Repeat the procedure by using organic solvent - acetone.

2. Reaction with bromine
Place 6 clean, dry test tubes in a rack, and add 2 mL of a solvent (hexane)to each.
Add nothing to # 1 (control), about 0.5 g of cholesterol to # 2, 5 drops of glycerol to # 3, about 0.5 g of stearic acid to # 4, 5 drops of oleic acid to # 5, and 5 drops of vegetable oil to # 6. Add 2 drops of bromine solution to tube #1. Mix and note whether the bromine color has faded at 10 to 30 seconds interval following the bromine addition. Repeat the procedure for each of the 5 remaining tubes in succession, and record your observation.

3. Saponification (preparing a soap)
Place about 20g of coconut oil into 50 mL beaker. Heat the beaker with oil gently in a hot water bath. A 400 mL beaker containing about 150 mL of hot tap water can serve as a water bath. Accurately weigh about 3.5 g of NaOH pellets (do not touch them with your fingers!), put them into 50 mL flask and dissolve completely into 10 mL of distilled water. Add the warm prepared NaOH solution to the warm oil and stir to ensure complete mixing of the two layers. Maintain mixing (for 20-30 minutes) until the mixture gets uniform and begins to thicken. If the mixture still is not uniform, place 50-mL beaker with the mixture on a top of hot plate and continue heat it up and mixing for edditional 5-10 min. Cool the mixture down and take about 5g of it (one spatulaful) for the next experiment #4.
If desired, stir 1 drop of perfume and 1 drop of coloring into the rest part of soup and immediately pour the mixture into a cup. Place a cup on the ice bath to solidify the product.


4. Properties of soap

A. Preparing of soap solution

Place about 5 g of the soap you prepared in a 100 mL beaker containing 50 mL of water. Warm the beaker with its content to dissolve the soap.

B. Basicity

Test the soap solution with pH paper. Is solution acidic, basic, or neutral? What is the approximate pH value of the solution?

C. Effect of acid on soap

Place about 5 mL of a soap solution into a test tube # 1. Place the same amount of the soap solution into a test tube # 2 and add 5 mL of 0.1 M HCl solution. Take about half of the solution from test tube # 2 and place it into the test tube # 3. Add 3 mL of 0.1 M NaOH solution to the test tube # 3.

Effect of hard water on soap

Place 5 mL of a soap solution into each of four test tubes (# 1-4). Add 5 mL of distilled water to # 1; 5 mL of tap water to # 2; 2 drops of 5% MgCl2 solution to # 3; and 2 drops of 5% CaCl2 solution to # 4.



Lab. # 12: AMINO ACIDS AND PROTEINS

Assignment:
1. Compare physical properties of aminoacids (AA) and proteins.
2. Investigate chemical properties of AA.
3. State the purpose of each test for proteins.
4. Explain the effect of each factor (temperature, organic solvents, salts of heavy metals) on changing structure of protein during its denaturation.

Objective:
To learn and compare physical and chemical properties of amino acids and proteins.

Materials: 10 mL graduated cylinder, test tubes, 100 mL beakers, glass rod, plastic droppers

Chemicals:
Solutions: Amino acids: 1% glycine; 1% glutamic acid; 1% lysine;
Proteins: 1% albumin, 1% gelatin, 1% whey protein;
0.1 M HCl; 10% NaOH; 5% CuSO4; 6M HCl; concentrated HNO3;
0.1 M lead(II) acetate solution, Pb(C2H3O2)2
Indicators: pH paper
Organic solvents: ethanol, acetone

Safety rules:
Wear safety goggles

Procedure:
1. Acidity/basicity of amino acids and proteins

Place 1 drop of the glycine solution on the pH paper. Is solution acidic, basic, or neutral? What is the approximate pH value. Repeat the procedure for the other amino acids and for the protein solutions.

2. Reaction of amino acids with Cu2+

Place 10 drops of CuSO4 solution into a test tube # 1. Add 5 drops of NaOH solution. Take about half of the test tube content into test tube #2 and add 5 drops of glycine solution to the test tube.

3. Tests for proteins

A. Biuret test (the presence of peptide linkage)

Place 3 mL of the albumin, gelatin and whey protein solution into the each test tube
# 1, # 2, and # 3 respectively. Add 3 mL of 10% NaOH solution to each test tube, and then add 2 mL of the CuSO4 solution to each test tube. Do not shake the test tubes! The appearance of violet color of the solution indicates the positive test result.

B. Xanthoproteic test (the presence of the phenyl group, – C6H5)

Prepare three test tubes with protein solutions as in previous step. Add 3 drops of concentrated HNO3 to each test tube. Heat the content of the test tubes in water bath until solutions change color.

C. Test for sulfur in proteins

Prepare three test tubes with protein solutions as in previous step. To each test tube add 2 mL of the NaOH solution. Heat the test tubes in a boiling water bath for 1 to 2 minutes. Remove the test tubes from the water bath and add 4 drops of lead(II) acetate solution, Pb(C2H3O2)2 and note the results. Add 2 to 3 mL of diluted (6M) HCl with light warming until the dark color disappears. Carefully smell and note the odor of the solution.

5. Denaturation of proteins

A. Temperature

Prepare three test tubes with protein solutions as in previous step. Heat the test tubes in a boiling water bath for 5 min.

B. Organic solvents

Prepare three test tubes with protein solutions as in previous step. To each test tube add 3 mL of ethanol. Repeat the procedure by using acetone instead of ethanol.

C. Salt of heavy metals

To a clean test tube add 3 mL of each of the protein solutions. Add 2 mL of
lead (II) acetate solution, Pb(C2H3O2)2. Repeat the procedure by using 5% CuSO4 solution.


LATTC

Chem 70

Dr.Darmanyan

EXAM # 1
(Ch.19,20,21)

Review sheet

A. Introduction
Organic compounds (definition, properties of carbon atom, classification of hydrocarbons, functional groups)

B. Alkanes
1. Homologous series
2. Structure (hybridization, sigma bond, bond angle)
3. Isomerism
4. Nomenclature. Alkyl groups.
5. Physical properties
6. Chemical properties (substitution, elimination, oxidation, combustion, cracking)
7. Sources and preparation

C. Cycloalkanes
(structural formulas, positional isomerism)

D.Alkenes
1. Classification of unsaturated hydrocarbons
2. Homologous series
3. Isomerism (carbon skeleton, positional, geometrical: cis-trans)
4. Nomenclature. Alkyl groups
5. Structure (hybridization, sigma and pi bonds, bond angle)
6. Physical properties
7. Chemical properties (addition, oxidation, combustion)

E. Alkynes
1. Homologous series
2. Isomerism
3. Nomenclature
4. Structure (hybridization, sigma and pi bonds, bond angle)
5. Chemical properties (addition, oxidation, combustion)

F. Arenes
1. Structure of benzene
2. Isomerism (o-, m, p- isomers)
3. Nomenclature
4. Chemical properties (substitution, side chain oxidation, combustion, addition)

G. Macromolecules

1. Classification
2. Polymerization reaction (addition polymerization, copolymerization, condensation)
3. Usage of polymers


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EXAM # 2
(Ch.22, 23)

Review sheet

A. Alcohols

1. Classification
2. Isomerism
3. Nomenclature
4. Physical properties
5. Chemical properties
a. Acidic properties
b. Esterification
c. Substitution of OH-group
d. Oxidation
e. Intramolecular dehydration (Saytzeff’s rule)
f. Intermolecular dehydration (ethers formation)
6. The important alcohols for living systems
a. Ethanol
b. Glycerol

B. Phenols
1. Classification
2. Nomenclature
3. Chemical properties
a. Acidic properties
b. Substitution of hydrogen in benzene ring

C. Ethers
1. Nomenclature
2. Preparation
3. Specific properties

D. Thiols
1. Nomenclature
2. Specific properties

E. Aldehydes

1. Classification
2. Isomerism
3. Nomenclature
4. Physical properties
5. Chemical properties
a. Addition
b. Self addition (aldol condensation)
c. Reaction with amino group containing substances
d. Oxidation

F. Ketones
1. Nomenclature
2. Specific properties

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EXAM # 3
(Ch. 24, 25)

Review sheet

A. Carboxylic acids
1. Classification
2. Isomerism
3. Nomenclature
4. Physical properties
5. Chemical properties
a. Acidic properties (dissociation, neutralization reactions)
b. Substitution of OH-group (esterification, formation of
acylchlorides and amides)
c. Anhydrides formation
6. Preparation of carboxylic acids
a. Oxidation of hydrocarbons, alcohols, aldehydes
b. Hydrolysis of esters, amides, acylchlorides

B. Esters
1. Nomenclature
2. Physical properties
3. Chemical properties
a. Hydrolysis (by enzymes, acids, bases)
b. Condensation (formation of polyesters)
4. Preparation of esters
a. Esterification reaction
b. Reaction between alkylhalides and salts of carboxylic acids

C. Amides
1. Nomenclature
2. Chemical properties
a. Hydrolysis
b. Condensation with carbonic acids

D. Amines
1. Classification
2. Isomerism
3. Nomenclature
4. Chemical properties
a. Basic properties (dissociation, salts formation)
b. Formation of amides
5. Preparation of amines
a. Alkylation (ammonia, amines)
b. Reduction (amides, nitriles, nitrocompounds)

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EXAM # 4
(Ch. 26, 27)

Review sheet

A. Stereoisomerism
1. Chiral atom
2. Optical properties
3. Enantiomers
4. Diastereomers
5. Racemic mixtures
6. Meso compounds

B. Monosaccharides
1. Classification
2. Fisher projection formulas
3. Enantiomers (D- and L-forms)
4. Opened- and cyclo- forms
5. Epimers
6. Anomers (α- and β- forms)
7. Pyranose and furanose forms
8. Systematic names
9. Reactions:
a) oxidation (Cu2+ + OH- , warm HNO3)
b) reduction (H2)
c) ether formation (CH3OH)
10. MC in living organisms

C. Disaccharides
1. Reducing and Nonreducing
2. Maltose, Lactose, Sucrose (formulas, names)
3. Reactions:
a) hydrolysis
b) oxidation (Cu2+ + OH-)

D. Polysaccharides
1. Starch
a) amylose
b) amylopectin
2. Glycogen
3. Cellusose
4. Physical properties
5. Chemical properties:
a) hydrolysis
b) reactions of OH group


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FINAL EXAM
(CH.28, 29, 30, 31)

Review sheet

Lipids
(function, structure, properties)

Simple lipids
 Fatty acids (palmitic, oleic, linoleic, linolenic, -3, -6)
 Fats and oils (mono- and triacylglycerols, physical properties, hydrogenation, saponification, soaps)
 Waxes

Compound lipids
 Phospholipids (phosphatidic acids, lecitins, cephalins)
 Sphingolipids (sphingomyelins,glycolipids)

Steroids
Fat soluble vitamins (A,D,E,K)

Amino acids

Classification (-, -, - …, aliphatic, aromatic, heterocyclic, mono- and diamino acids,
mono- and dicarbonic acids, hydroxy- and sulfur containing amino acids)
Structure glycine, alanine, phenylalanine,glutamic acid, lysine, serine, cyctein,
tryptophan;
bipolar ion, stereoisomerism)
Properties
(physical properties, amphoterism, acidity/basicity)
Functions (
essential amino acids, protein formation)

Peptides (peptide bond, nomenclature,, functions)

Proteins
Functions
Structure of protein component (primary, secondary, tertiary, quaternary, shapes, types of bonding)
Properties (solubility, denaturation, hydrolysis)

Nucleic acids
Nucleotides (structure)
Polynucleotides (DNA, RNA – structure, shape, hydrogen bonding)
Functions (heredity, genes, synthesis of protein)

Enzymes Function
Classification and Nomenclature
Properties (specificity, transition state, temperature and pH factors, inhibition and activation)

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