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CBSE Class 12 Compartment Exam Syllabus 2025
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CBSE Class 12 Compartment Exam Syllabus 2025
March 6, 2025CBSE Class 12 Important Dates 2025
March 3, 2025CBSE Class 12 Previous Year Question Papers
March 3, 2025CBSE Class 12th Important Topics 2025
February 28, 2025CBSE Syllabus for Class 12 Chemistry 2025
February 27, 2025CBSE Class 12 Important Chapters with Exam Strategy
February 27, 2025CBSE Class 12 Biology Notes: Important Chapters
February 27, 2025CBSE Important Questions Class 12 Maths
February 27, 2025CBSE Class 12 Mock Test Series 2025 – Attempt Latest Papers
February 27, 2025CBSE Class 12 Physics Notes 2024-25: Download PDF
February 27, 2025Test for Alcohols: Alcohols are organic compounds with the functional group
While naming alcohols, the suffix
The general formula of alcohol homologous series is
The homologous series of alcohols consists of methanol, ethanol, propanol, and butanol with chemical formulas of
Study Structure of Alcohol Here
Based on the number of hydroxyl groups attached to the parent chain, alcohols are classified as monohydric (contain only one
When the
To distinguish alcohols from other functional groups, the following tests are performed-
Alcohols react with active metals like sodium with a brisk effervescence to liberate hydrogen gas. A colourless solution of sodium ethoxide,
The absence of phenyl or carboxyl groups favours this reaction.
Alcohol reacts with
A fruity-smelling compound called esters is formed when alcohols react with carboxylic acids. The reaction between alcohol and carboxylic acid is known as esterification and is a slow and reversible reaction catalysed by an acid such as concentrated sulphuric acid.
The chemical reaction is given below.
Alcohols react with ceric ammonium nitrate
The red colour also disappears after resting the reaction mixture.
The chemical reaction is given below.
Alcohols react with acid halides to form esters with the liberation of hydrogen chloride gas. The hydrogen chloride gas reacts with ammonium hydroxide to give white fumes of ammonium chloride.
The chemical equation is given below.
Secondary alcohols, ketones and acetaldehyde show a positive iodoform test. A yellow precipitate of iodoform is formed when the given compound is heated with sodium hydroxide solution and iodine.
The chemical reactions are given below
Primary, secondary and tertiary alcohols react with Lucas reagent (zinc chloride and concentrated hydrochloric acid) at different rates. This reagent forms a cloud-like appearance on reacting with alcohols. Tertiary alcohols react immediately; secondary alcohols react slowly to form a cloud-like appearance after
The chemical reactions are given below.
Cloudiness appears immediately
Cloudiness appears within five to ten minutes
Cloudiness does not appear
Victor Meyer’s test is an important test to distinguish between primary, secondary and tertiary alcohols. It is an organic compound that has a functional group
The reagents used in the Victor Meyers test are
In the test, three different colours are observed for different alcohols. These are listed below.
Blood Red Colour | Primary Alcohol |
Blue Colour | Secondary Alcohol |
No Colour Change | Tertiary Alcohol |
When primary alcohol reacts with the reagents (
Phenols are compounds that contain a hydroxyl group attached to an aromatic ring. The simplest phenol is
The following tests can detect the phenolic group:
Phenol is weakly acidic and gives a red colour with blue litmus paper. Phenol dissociates in water to form phenoxide ions and water. This is represented as follows:
Phenols react with neutral ferric chloride solution to give a coloured complex. For example, phenol gives a complex of violet colour as follows:
Observations:
Phenol in concentrated sulphuric acid reacts with sodium nitrite to form a deep blue or green coloured complex. The blue or green colour changes to red or brown colour on being treated with water. The red colour is due to the formation of indophenol, which changes to blue or green by adding strong alkali. The blue or green colour is due to the formation of indophenol anion.
Note:
This test is not given by Nitrophenols and
Phenols in the presence of concentrated
Red | |
Bluish Purple | |
No Colour | |
Catechol | Usually, blue takes a longer time to appear |
Resorcinol | Green Fluorescent Colour of Fluorescein |
The Tests for the alcohol group (Distinguishing test from other functional groups) are tabulated below:
Test | Procedure | Observation |
Sodium metal Test | Reagent: The organic compound to be tested is taken in a dry test tube. To it, To the above solution, a small piece of sodium metal is added. | A brisk effervescence indicates the presence of an alcoholic group |
Ester Test | To the above solution, The mixture is heated in a water bath for The hot mixture is poured into a beaker containing cold water. | A fruity smell confirms the presence of an alcoholic group. |
Ceric Ammonium Nitrate Test | Reagent: The reagent is prepared by dissolving A few drops of ceric ammonium nitrate reagent is added to the above solution and shaken. | A wine red coloured precipitate shows the presence of an alcoholic group |
Acetyl Chloride Test | To the above solution, To the filtrate, A glass rod dipped in ammonium hydroxide solution is brought near the mouth of the test tube. | The formation of white fumes indicates the presence of alcohol |
Iodoform Test | Reagent: A dilute solution of sodium hydroxide solution is added dropwise to the above solution until the brown colour of iodine is discharged. The mixture is heated gently in a water bath. | The formation of yellow precipitate shows the presence of alcohol |
Tests for distinguishing primary, secondary and tertiary alcohols
Test | Procedure | Observation |
Lucas Test | Dissolve | Cloudiness appears immediately Cloudiness appears within five to ten minutes Cloudiness does not appear |
Victor Meyer’s Test | To the given organic compound, concentrated hydrogen iodide or red phosphorus and iodine are added. To the above solution, silver nitrite is added to produce nitroalkane. Nitroalkane is then treated with nitrous acid | Primary alcohol – Blue red Secondary alcohol – red Tertiary alcohol – No change |
Q.1. Which alcohol gives red colour in Victor Meyer’s test?
Ans: Primary alcohols or
Q.2. Which alcohol gives Lucas test immediately?
Ans: Primary alcohols or
Q.3. What is acidic dehydration of alcohol?
Ans: Alcohol reacts with protic acids and loses a molecule of water to form alkenes. As the reaction involves the removal of the water molecule, these are generally known as dehydration of alcohols. It is an example of an elimination reaction. The rate of the reaction differs for the primary, secondary and tertiary alcohols.
Q.4. What are the qualitative tests for alcohol?
Ans: The qualitative tests for alcohols are –
(i) Chromic Acid Test (or Jones Oxidation)
(ii) Lucas Test using
(iii) Iodoform Test.
Q.5. Which alcohol gives a positive iodoform test?
Ans: Ethanol is the only primary alcohol to give the triiodomethane (iodoform) reaction. However, secondary alcohols with a methyl group attached to the carbon with the
Study Preparation of Alcohols Here
We hope this article on tests for alcohols is helpful to you. If you have any queries about this page or in general about the alcohols test, ping us through the comment box below and we will get back to you as soon as possible.
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