Revision Notes for CBSE Class 12 Chemistry Chapter 8 (Aldehydes, Ketones and Carboxylic Acids) - Free PDF Download
Section-A (1 Mark Questions)
The formula of chloral is _______?
Ans. The formula of chloral is CCI3CHO.
Why is there a large difference in the boiling points of butanal and butan-1-ol?
Ans. Boiling points of aldehydes are lower than those of alcohols of similar molecular masses due to absence of intermolecular hydrogen bonding. This bonding makes the alcohol more stable at certain level of temperatures.
Formalin is an aqueous solution of ________?
Ans. Formalin is the aqueous solution of formaldehyde, specifically 40% aqueous solution of formaldehyde. Or we can say that in 100 ml of solution, 40 ml is formaldehyde and 60 ml is water.
Write a chemical test to distinguish between aldehyde and ketone.
Ans. Aldehydes and ketones can be distinguished By Tollen’s test. Aldehydes give a silver mirror on reacting with Tollen’s reagent whereas ketones will not react.
What is the function of $BaSO_{4}$ in rosenmund reaction?
Ans. $BaSO_{4}$ acts as a catalytic poison which prevents further reduction of aldehyde to alcohol.
Why HCOOH does not give HVZ reaction while CH3 COOH does?
Ans. CH3 COOH contains α-hydrogen and hence give HVZ reaction but HCOOH does not contain α-hydrogen and hence does not give HVZ reaction.
Why is oxidation of alcohols to get aldehyde carried out under controlled conditions?
Ans. It is because aldehydes get further oxidised to acids so, oxidation of alcohols to aldehydes needs to be controlled.
What type of aldehydes undergo Cannizaro reaction?
Ans. Aromatic and aliphatic aldehydes which do not contains α-hydrogen give cannizaro reaction.
Name the reagents used in the following reaction.
Ans. LiA1H4
Section-B (2 Marks Questions)
Arrange the following in decreasing order of their acidic strength. Give explanation for the arrangement. C6H5COOH, FCH2COOH, NO2CH2COOH.
Ans. NO2CH2COOH > FCH2COOH > C6H5COOH
Electron withdrawing groups increase the acidity of carboxylic acids by stabilizing the conjugate base through delocalization of the negative charge by inductive and/or resonance effects.
Which reagent is used in Gattermann Koch aldehyde synthesis ?
Ans. Gattermann-Koch reaction is a process in which the benzene is converted into benzaldehyde. When benzene is reacted with carbon monoxide and hydrochloric acid in presence of AlCl3 or CuCl, there is formation of benzaldehyde. The reaction is given below:
How to convert Toluene to m-nitro benzoic acid
Ans.
Nucleophilic addition reaction will be most favoured in CH3CHO or (CH3)2C=O?
Ans. Both aldehydes and ketones are very reactive towards the Nucleophilic addition reaction, because carbonyl group is a very reactive group. So, the reactivity of the carbonyl group can be decided on the magnitude of the positive charge on the carbonyl group. So, the compound that have least methyl group will have the highest positive charge and will have highest reactivity. So, CH3CHO will have highest reactivity.
Write the product in the following reaction.
Ans.
Why aromatic compounds does not undergoes Fehling’s test
Ans. In aromatic aldehyde, the -CHO group is attached to the benzene ring. Due to resonance, carbonyl group’s C acquires a double bond character with benzene which is very strong to break. The oxidizing agents like Cu2+ are unable to break that bond, so such aldehydes are unable to show Fehling’s test.
Product in following reaction is $CH_{3}MgI+HCHO\rightarrow$ Product
Ans. Here CH3MgI is a Grignard reagent. This reagent is used for alkylation. Upon addition of water, an alcohol is obtained.
The reaction is: $CH_{3}MgI+HCHO\xrightarrow[H^{+}]{H_{2}O}CH_{3}CH_{2}OH$
When ethanal is treated with Fehling’s solution, which precipitate is obtained?
Ans. Fehling’s test is used for the presence of aliphatic aldehyde in the compound. Alkaline solution of $CuSO_{4}$ containing some Rochelle salt is known as Fehling’s solution. When the aliphatic aldehyde like ethanal, is treated with Fehling’s solution, red ppt. is formed. And this red precipitate is formed by the compound cuprous oxide having formula $(Cu_{2}O)$ .
Write the products formed when ethanal react with $C_{6}H_{5}CHO$ in the presence of dilute NaOH.
Ans.
PDF Summary - Class 12 Chemistry Aldehydes, Ketones and Carboxylic Acids Notes (Chapter 8)
While going through class 12 revision notes chapter 8 students will find themselves getting comfortable with the terms and concepts of the chapter. The NCERT solutions chapter 8 class 12 chemistry revision notes are prepared to clear any doubts students might have thus given students a better grasp over the subject.
Given below is the list of subtopics included in the chapter. For a detailed explanation of these topics, refer to class 12 chemistry revision notes solution chapter 8. This chapter comes under organic chemistry, which can be complex and overwhelming when first starting. Students can go through the class 12 chemistry revision notes solution chapter 8 to understand these concepts better. This chapter talks about the compound with a carbonyl group. A carbonyl group contains a carbon-oxygen double bond.
Aldehydes and Ketones.
Nomenclature.
Nature of carbonyl groups.
Physical and chemical properties.
Nucleophilic addition.
Carboxylic acids.
Preparation of carboxylic acids.
Properties and uses.
Revision Notes Class 12 Chemistry Chapter 8
Given below is a brief explanation of the important concepts in the chapter. For a detailed explanation of the same, refer to aldehydes, ketones and carboxylic acids class 12 chemistry revision notes. revision notes class 12 chemistry chapter 8 contains a comprehensive explanation of all the topics and solutions of the questions.
Aldehydes and Ketones
Aldehydes and ketones are commonly named by adding an aldehyde or phenone to the compound name.
In IUPAC nomenclature, we substitute the -e with an -al and -one in the case of aldehyde and ketone respectively.
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By oxidation of primary and secondary alcohols, we obtain aldehydes and ketones. Also, the dehydrogenation of alcohols gives us aldehyde and ketones. Also, we can obtain aldehyde and ketone on ozonolysis of alkenes and hydrolysis of alkynes.
Carboxylic Acids
Carboxylic acids are commonly named by adding the suffix -ic acid. In IUPAC nomenclature the -e is replaced by -oic acid.
Preparations:
On oxidising primary alcohols and aldehydes with common oxidising agents such as potassium permanganate or potassium dichromate, we readily obtain carboxylic acids.
RCH2OH ⟶ RCOOH
On oxidation of alkylbenzenes and further hydrolysis of the intermediate formed, we obtain carboxylic acids.
Nitriles are hydrolysed to corresponding amides and on further reacting with H+ or OH- we obtain carboxylic acids. Amides readily give carboxylic acids on hydrolysis.
Grignard reagents on reacting with dry ice in the presence of ether give carboxylic acids salts which on hydrolysis gives us carboxylic acids
Hydrolysis of esters in the presence of an acid readily gives carboxylic acids.
CBSE Class 12 Revision Notes and Key Points
Class 12 Chemistry Revision Notes for Chapter 8 - Aldehydes, Ketones and Carboxylic Acids are extremely important and helpful for students appearing for CBSE Class 12 Chemistry exam. These revision notes provide important key points, formulas, equations and concepts that students should go through to enhance the effectiveness of preparation while revising the syllabus.
These notes will save your time during exam days by giving you an overview of Chapter 8 - Aldehydes, Ketones and Carboxylic Acids. The revision notes are available in PDF format so you can download them now and take a printout to study later. Check out Vedantu’s revision notes for all of the following subjects.
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FAQs on Aldehydes Ketones and Carboxylic Acids Class 12 Notes CBSE Chemistry Chapter 8 (Free PDF Download)
1. How are Aldehydes Prepared?
Aldehydes can be prepared by any of the following reactions.
Rosenmund Reaction
From the hydrogenation of acid chloride with palladium and barium sulphate as catalysts we prepare aldehydes.
Benzoyl chloride ⟶ benzaldehyde (catalyst - H2, Pd-BaSO4)
Stephen Reaction
Nitriles reacting with stannous chloride in the presence of hydrochloric acid is reduced to imine, and its hydrolysis gives us aldehyde.
RCN + SnCl2 + HCl ⟶ RCH = NH ⟶ RCHO
Etard Reaction
Methylbenzene on reacting with chromyl chloride gives a chromium complex which on hydrolysis gives us the corresponding benzaldehyde.
Methyl benzene + CrO2Cl2 ⟶ Chromium complex ⟶ benzaldehyde
2. What are the Uses of Aldehydes, Ketones and Carboxylic Acids?
Some common uses of these compounds are:
Aldehydes and Ketones - These are commonly used as solvents. Butyraldehyde, acetophenone and camphor are used for their odours and flavours. Acetone and ketones are commonly used as industrial solvents. Formaldehyde is commonly used in the production of formalin solutions which is used in preserving biological specimens. Acetaldehyde is used as a starting material in the manufacture of commonly used drugs and polymers.
Carboxylic Acids - In perfumes, esters of benzoic acid are used. It is also used in preserving food and fatty acids are commonly used in the production of soaps and detergents.
3. What are aldehydes, ketones and carboxylic acids?
Aldehydes, Ketones and Carboxylic acids are discussed in Chapter 8 of Class 12 Chemistry. The definitions for these terms are clearly stated in the following points:
The organic compounds which have a carbonyl group attached to a hydrogen atom and alkyl group forms aldehydes.
The organic compounds in which the carbonyl group is attached to two alkyl groups form ketones.
The hydrocarbon compounds whose carboxyl group substitutes one or more of the hydrogen atoms in the hydrocarbon forms carboxylic acids.
4. What are the name reactions in Aldehydes, Ketones and Carboxylic acids?
Name reactions are those chemical reactions that are named after the people who discovered them and the chapter of ‘Aldehydes, Ketones and Carboxylic Acids’ of Chapter 8 of Chemistry for Class 12 students seems to be full of them. Students need to be thorough with all the name reactions to score well for their organic chemistry part of the exam:
Rosemund’s Reduction Reaction
Itard Reaction
Wolf-Kishner Reaction
Clemmenson’s Reduction Reaction
Cannizzaro Reaction
Kolbe-Schmitt Reaction
Hell-Volhard Zelinsky Reaction
5. Which of the functional groups is common to aldehydes, ketones and carboxylic acids?
Aldehydes have one carbonyl group while ketones have two. The functional group common to both Aldehydes and Ketones is the carbonyl group. For carboxylic acids, their weak nature makes the hydrogen of the hydroxyl group ionizable. Thus, carboxylic acids have a carboxyl group. In the case of aldehydes and ketones, their carbonyl group is at the end and the middle respectively. The carboxyl functional group is denoted as -CO, while the carboxyl group is denoted as -COOH.
6. How do NCERT Solutions benefit students in learning Chapter 8 of Class 12 Chemistry?
The chapter “Aldehydes, Ketones and Carboxylic Acids” necessitates a good comprehension of ideas to attempt and answer problems. The revision notes from Vedantu have fragmented the relevant concepts that assist students to understand and comprehend the subjects better. The chapter is embellished with ideas, equations, diagrams and other visual aids, and the answers are created under expert guidance. The answers are correct, and they are easily available on the Vedantu app also. The resources are free of cost.
7. What are the important topics in Chapter 8 of Class 12 Chemistry?
The chapter ‘Aldehydes, Ketones and Carboxylic Acids’ forms an important and major part of Class 12 Organic Chemistry. Thus, this becomes a chapter that students can not skip and as such, the chapter is full of important topics that students need to be thorough with. The important topics are as follows.
Aldehydes
Ketones
Carboxylic acids
Hydration of Alkynes
Friedel Crafts Reactions
Formation of Cyanohydrins
Formation of Alcohols
Wolff-Kishner Reduction
Halogenation
Cannizzaro Reaction
Chemical test- Tollen’s reagent and Ferric Chloride
Other reactions.