1.27: Experiment_727_Organic Compound Functional Groups__1_2_0

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Student Name

Laboratory Date:

Date Report Submitted:

___________________________

Student ID

Experiment Number and Title

Experiment 727: Organic Compound Functional Groups

Section 1: Purpose and Summary

Determine the solubility of different organic compounds.
Determine the reactivity of functional groups with various test reagents.
Identify an unknown organic compound based on its functional group.

The functional group in an organic compound is the part of the molecule that undergoes a structural change during a chemical reaction. It also influences the solubility of the compound in water or in organic solvents. Certain chemical tests will allow the identification of a specific functional group in a compound. The functional groups that will be analyzed in this experiment are alcohols, phenols, aldehydes, ketones, carboxylic acids, and amines.

In this experiment, students will determine the solubility of different organic compounds in water, dilute acid, or dilute base. This solubility can provide information on what functional group is present or whether the compound has a high or low formula mass. Students will perform chemical tests for known organic compounds to suggest the presence or determine the absence of a specific functional group in the compound. Students will use the results of both solubility and functional group tests to generate experimental data that will help them identify an unknown sample.

Section 2: Safety Precautions and Waste Disposal

Safety Precautions:

Use of eye protection is recommended for all experimental procedures.

Wash your hands after working with organic reagents and solutions. Do not eat in the laboratory.

Waste Disposal:

While you are doing the experiment, collect all waste into a beaker.

When you are finished with the experiment, pour the contents of the waste beaker into the organic waste container in the fume hood.

Section 3: Procedure

Important: Use clean, dry and labeled small or medium-size test tube for each test.

Known compounds include: 2-butanone, benzaldehyde, n-butyl bromide, cyclohexene, 2-propanol, tert-butyl alcohol, isobutyl alcohol, propanoic acid, triethyl amine, phenol.

Part 1: Solubility Tests

Low molecular weight hydrocarbons are soluble in water, while high molecular weight ones are not. Carboxylic acids are soluble in basic solutions, while amines are soluble in acidic solutions.

A. Solubility in water

Into a small test tube, place 5 drops of known sample. If the compound is in solid form, add a pea-sized sample into the test tube.

To each sample, add 10 drops of laboratory water and mix thoroughly by holding the top of the test tube and flicking the bottom with your finger. Does the sample dissolve in water? (Note: A liquid sample that is insoluble in water forms a second liquid layer.) Record your observations.

If the compound is soluble in water, test its acidity or basicity using litmus paper. If blue litmus turns red, it is acidic. If red litmus turns blue, it is basic. Record your observations.

B. Solubility in 5% NaOH

Into a small test tube, place 5 drops of known sample. If the compound is in solid form, add a pea-sized sample into the test tube.

To each sample, add 10 drops of 5% NaOH. Mix thoroughly by holding the top of the test tube and flicking the bottom with your finger. Record your observations.

C. Solubility in 5% HCl

Into a small test tube, place 5 drops of known sample. If the compound is in solid form, add a pea-sized sample into the test tube.

To each sample, add 10 drops of 5% HCl. Mix thoroughly by holding the top of the test tube and flicking the bottom with your finger. Record your observations.

Part 2. Functional Group Tests

A. Silver Nitrate Test for Alkyl Halides and Carboxylic Acids

n-butyl bromide, propanoic acid

Into a clean, dry small test tube, place 20 drops of 0.1 M solution of AgNO₃ in 95% ethanol.

Add one drop of known sample and mix thoroughly. Observe for the formation of white or yellow precipitate.

If no reaction is observed within five minutes at room temperature, warm the mixture in a beaker of boiling water (on a hot plate and add boiling chips to the bath), and observe any change. Record your observations.

If precipitate forms, add several drops of 1 M HNO₃ and note any changes, particularly dissolution of precipitate. Record your observations.

B. Chromic Acid Test for Alcohols and Aldehydes

2-propanol, tert-butyl alcohol, isobutyl alcohol, benzaldehyde

Into a small test tube, place 20 drops of known sample.

Add one drop of the chromic acid reagent. Mix thoroughly by holding the top of the test tube and flicking the bottom with your finger. Note the color change of the solution. A positive test gives a change in color of the reagent from orange to green. A blue color may also be observed and is a positive test. Record your observations.

C. Bromine Test for Alkanes and Alkenes

cyclohexene

Into a small test tube, add 5 drops of known sample.

To each sample, add 1 drop of 2% solution of bromine in dichloromethane. Mix thoroughly by holding the top of the test tube and flicking the bottom with your finger. Note the time required for the decolorization of the bromine solution. Record your observations.

D. Ferric chloride Test for Phenols

Phenol

Into a small test tube, mix 2 – 3 drops of known sample and 2 drops of laboratory water.

Add 1 – 2 drops of 2.5% FeCl₃. Stir the mixture well with a stirring rod. Observe immediately and note the color change of the solution. A positive test is indicated by the change in color of the FeCl₃ solution from yellow to a blue green, violet, grey, or red.

E. Iodoform Test for Ketones (carbonyl on C-2) or 2^o Alcohols (OH on C-2)

2-propanol, 2-butanone

Into a small test tube, add 2 – 3 drops of known sample and 1 mL of laboratory water. Mix thoroughly by swirling.

Add 1 mL of 10% NaOH, followed by 1.5 mL of 0.1 M I₂/KI solution. Note the disappearance of the brown color of the I₂/KI solution followed by the formation of a light-yellow precipitate. Record your observations.

F. 2,4-DNP Test for Aldehydes and Ketones

benzaldehyde, 2-butanone

Into a small test tube, place 20 drops of 2,4-DNP solution.

Add 2 drops of the known sample and mix thoroughly by swirling. Observe for the formation of an orange or red-orange precipitate. Record your observations.

G. TCICA Test for Alcohols

2-propanol, tert-butyl alcohol, isobutyl alcohol

Into a small test tube, add 10 drops of the TCICA solution in acetonitrile (30 mg/mL), one drop of 1 M HCl, and one drop of the known sample.

Mix thoroughly by holding the top of the test tube and flicking the bottom with your finger. Note the time required for the precipitate to form. Record the elapsed time.

Part 3: Unknown Compound

Obtain a sample of an unknown compound from your instructor. Record the identification code of the unknown. This is very important! With no identification, your work cannot be graded.

Perform solubility and functional group tests and tabulate your results.

Identify the functional group of the unknown sample based on your results.

Section 4: Data and Results

KNOWN Compound Solubility and Functional Group Tests

Part 1: Solubility Tests

Known Compounds	Observations			Conclusions
Known Compounds	Water/Litmus	5% NaOH	5% HCl	Conclusions
n-butyl bromide
isobutyl alcohol
2-propanol
tert-butyl alcohol
phenol
benzaldehyde
2-butanone
propanoic acid
triethylamine
cyclohexene

Part 2: Functional Group Tests

Silver Nitrate Test

Compounds Tested	Observations
n-butyl bromide
propanoic acid

Chromic Acid Test

Compounds Tested	Observations
isobutyl alcohol
2-propanol
tert-butyl alcohol
benzaldehyde

Bromine Test

Compound Tested	Observations
cyclohexene

Lucas Test

Compounds Tested	Observations
isobutyl alcohol
2-propanol
tert-butyl alcohol

Ferric Chloride Test

Compound Tested	Observations
phenol

Iodoform Test

Compound(s) Tested	Observations
2-propanol
2-butanone

2,4-DNP Test

Compound(s) Tested	Observations
benzaldehyde
2-butanone

TCICA Test

Compound(s) Tested	Observations
isobutyl alcohol
2-propanol
tert-butyl alcohol

UNKNOWN Compound Solubility and Functional Group Tests

Identification Code for the Unknown: _______________________

Fill the following table, where applicable.

Chemical Test	Observations	Conclusions
Water solubility/Litmus
5% NaOH solubility
5% HCl solubility
Silver Nitrate Test
Chromic Acid Test
Bromine Test
Ferric Chloride Test
Iodoform Test
2,4-DNP Test
TCICA Test

Functional group present in unknown: __________________________

High or low molecular weight? _______________________________

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