“ALCOHOLS”
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
Chromic acid test Ethyl alcohol
Results
Explanation
I.
5% Potassium dichromate and sulfuric acid
-Ethyl alcohol took 15 sec to change the color from orange to blue green.
Ethyl takes only 15 seconds to change color because it is a primary alcohols .
-n-butyl 30 sec, clear on top, Blue green at the bottom
N-butyl is also a primary alcohols.
N-butyl
Sec-butyl
-sec-butyl 15sec, blue green.
Sec-butyl is a secondary alcohols.
Tert –butyl is a
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
II. Lucas test Tert butyl
Lucas Reagents
Sec butyl alcohol
Results
Explanation
Cloudy
Tertiary
5 minutes, cloudy
Secondary
Do not react
Primary
Cloudy
tertiary
N-butyl alcohol
Benzyl
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 III. Esterification Ethyl Alcohol
Tert- butyl alcohol
Reagents
Results
Explanation
Acetic Acid and conc. Sulfuric acid
30 seconds, strong pleasant odor
The odor of the vapor tells that there’s an ester formed.
35 seconds, mild odor
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
Produced a yellow precipitate
Pale yellow precipitate of idoform is given by an alcohol contains the grouping CH3CH-OH R
V. Iodoform test Ethyl alcohol 10% drop of NaCl Isopropyl alcohol
Produced a yellow precipitate
Methyl alcohol
When added with NaOH the color became light and when put in hot water it became colorless.
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
KHSO4 (Potassium Bisulfite)
Pungent odor
KHSO4 produce an unsaturated aldehyde called acrolein from the glycerol.acrolein is recognised by its pungent odour forms basis of test for
VI. Acrolein test 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.
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.
