“ALCOHOLS”Activity no. 5

Objectives:

a.) To differentiate primary, secondary and tertiary alcohols.

b.) To distinguish the different classes of alcohols based on Lucas test.

c.)To classify the alcohols based on chromic acid test

Results and Discussions

Name of the Test Reagents Results Explanation

I. Chromic acid test

Ethyl alcohol

N-butyl

Sec-butyl

Tert-butyl

5% Potassium dichromate and sulfuric acid

-Ethyl alcohol took 15 sec to change the color from orange to blue green.

-n-butyl 30 sec, clear on top, Blue green at the bottom

-sec-butyl 15sec, blue green.

-tert-butyl does not change color.

Ethyl takes only 15 seconds to change color because it is a primary alcohols .

N-butyl is also a primary alcohols.

Sec-butyl is a secondary alcohols.

Tert –butyl is a tertiary alcohols.

Discussions:

Chromic acid test

-Used as a qualitative analytical test for the presence of primary and secondary alcohols. Primary alcohols are oxidized to carboxylic acid and secondary alcohols are oxidized to ketones while tertiary alcohols there is no reaction. In this test, 5% potassium dichromate and sulfuric acid removed the hydrogen from the -OH group, and a hydrogen from the carbon atom attached to the -OH. Tertiary alcohols don't have a hydrogen atom attached to that carbon.

Table and Results

Name of the test

Reagents Results Explanation

II. Lucas testTert butyl

Sec butyl alcohol

N-butyl alcohol

Benzyl

Lucas ReagentsCloudy

5 minutes, cloudy

Do not react

Cloudy

Tertiary

Secondary

Primary

tertiary

Discussion:

• In this test, Tertiary alcohols react immediately with Lucas reagent as evidenced by turbidity owing to the low solubility of the organic chloride in the aqueous mixture. Secondary alcohols react within five or so minutes (depending on their solubility). Primary alcohols do not react appreciably with Lucas reagent at room temperature. Hence, the time taken for turbidity to appear is a measure of the reactivity of the class of alcohol, and this time difference is used to differentiate between the three classes of alcohols.

- Tert-butyl and benzyl is a tertiary alcohols because it became cloudy in just a seconds, sec-butyl is a secondary alcohols because it takes 5 minutes to become cloudy. And n- butyl do not react therefore it is a primary alcohols.

Table and Results

Name of the test

Reagents Results Explanation

III. EsterificationEthyl Alcohol

Tert- butyl alcohol

Acetic Acid and conc. Sulfuric acid

30 seconds, strong pleasant odor

35 seconds, mild odor

The odor of the vapor tells that there’s an ester formed.

Discussion:

Esterification

• - The process in which an alcohol and an acid are converted to an ester and water.

• - Acetic acid reacts with ethyl alcohol in the presence of concentrated sulphuric acid as a catalyst to produce the ester, ethyl ethanoate. The reaction is slow and reversible. To reduce the chances of the reverse reaction happening, the ester is distilled off as soon as it is formed.

• - Tertiary alcohols don't work well with Fischer Esterification to yield a ester.

Table and Results

Name of the test

Reagents Results Explanation

IV. Special test for methyl alcohol

Water, resorcinol, conc. Sulfuric Acid.

It is hot in temperature with three layers, colorless, reddish, and light brown layer at the bottom.

Methyl alcohol is soluble in water that’s why it formed 3 layers.

Table and Results

Name of the test

Reagents Results Explanation

V. Iodoform test

Ethyl alcohol

Isopropyl alcohol

Methyl alcohol

10% drop of NaCl

Produced a yellow precipitate

Produced a yellow precipitate

When added with NaOH the color became light and when put in hot water it became colorless.

Pale yellow precipitate of idoform is given by an alcohol contains the grouping CH3CH-OH R

Discussion:

• Ethyl alcohol is the only primary alcohol to give the iodoform reaction. If "R" is a hydrocarbon group, then you have a secondary alcohol. Lots of secondary alcohols give this reaction, but those that do all have a methyl group attached to the carbon with the -OH group. No tertiary alcohols can contain this group because no tertiary alcohols can have a hydrogen atom attached to the carbon with the -OH group. No tertiary alcohols give positive test to the iodoform reaction.

Table and results

Name of the test

Reagents Results Explanation

VI. Acrolein test

Glycerol KHSO4(Potassium Bisulfite)

Pungent odor KHSO4 produce an unsaturated aldehyde called acrolein from theglycerol.acrolein is recognised by its pungent odour formsbasis of test for the presence of glycerol. 

Discussion:

• The importance of the acrolein test is to find out whether there is a presence of glycerin or fats in a compound. The method to perform the test is to heat a sample with potassium bisulfate. The test is positive if acrolein is released.

Answers to Questions

1.) What are the classes of alcohol based on the alkyl groups in them? Differentiate them

through their general formulas.

-The classes of the alcohol based on the alkyl groups are the primary, secondary, and

tertiary.

2.) Compare the relative ease oxidation primary, secondary, and tertiary butyl alcohol toward

acid dichromatic based on the time required for the solution to change color.

- Primary and secondary alcohols are oxidized rapidly to acids and ketones, respectively by

Cr+6 and the appearance of green color due to the reduced Cr+3 ion. Tertiary alcohols are not

easily oxidized, (however, over time in an acidic environment, they are dehydrated to alkanes).

3.) What is the significance of the Lucas test?

- In Lucas test, we use the Lucas reagent. Lucas reagent is a solution of zinc chloride in

concentrated hydrochloric acid, used to classify alcohols of low molecular weight. So the significance

of this test is that, we can classify if a compound is a primary, secondary, or tertiary alcohol.

4.) How will you distinguish ethyl alcohol from methyl alcohol?

- Ethanol (Ethyl Alcohol) is the portable form of alcohol found in alcoholic beverages. Ethyl alcohol

is obtained from the fermentation of sugars and starches, unlike methanol (methyl alcohol), which is

industrial solvent, is poison when swallowed.

5.) What is responsible for the characteristics odor of the acrolein test?

- The responsible for the characteristic odor of the acrolein test is to distinguish what odor it is, if it

is strong or mild odor.

6.) Give one important commercial method of preparing ethyl alcohol in the Philippines. Write the

chemical reaction involved.

- One important commercial method of preparing ethyl alcohol is making a wine form grapes. The

chemical reaction involved is, (sugar) C6H12O6 -> 2 C2H5OH + 2 CO2

Conclusion:

• We therefore conclude that based on chromic acid test, Ethyl Alcohol and n-butyl are primary alcohols because it oxidized to carboxylic acid and sec- butyl is a secondary alcohol because it oxidized to ketones. Tert-butyl is a tertiary alcohol, it does not react because of the absence of alpha hydrogen. Based on lucas test, Tertiary alcohols react immediately with lucas reagent, secondary alcohols takes 5 minutes or more to react with the reagent and primary alcohol do not react at all. In this experiment, we are able to differentiate the classes of alcohols based on the alkyl groups. Primary alcohols are attached to 1 carbon atom, secondary alcohols are attached to two carbon atoms and tertiary alcohols are attached to three carbon atoms.

GROUP 6

Abdurahman, Raiza Ayana I.

Paharul, Nurfaina A.

Tagayan, Arlyn H.