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Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Aldehyde and  Ketones
Preparation of Aldehydes 
a. Oxidation of primary alcohols
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Preparation of Ketones:
a) Oxidation of Secondary alcohols:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
d)  With Organometallics
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Reactions of Aldehydes and Ketones:
(a)  Aldol condensation
Aldehydes and ketones having alpha hydrogen atom:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

(b) Cannizzaro reaction:
Aldehydes and ketones having  no alpha hydrogen atom:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
When two carbonyl groups are present within a molecule, think of intramolecular reaction.
OH- will attack more positively charged carbon. In this case, it is right  >c=0 group.
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

(c) Formation of Keto Esters
Esters having a-hydrogen on treatment with a strong base e.g. C2H5ONa. Undergo self condensation to produce b-keto esters. This reaction is Claisen Condensation.
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

(d) Reformatsky Reaction
This is the reaction of a-haloester, usually an a-bromoester with an aldehyde or ketone in the presence of Zinc metal to produce b-hydroxyester.
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

(e) Pinacol-pinacolone Rearrangement
The acid catalysed rearrangement of 1,2 diols (Vicinal diols) to aldehydes or ketones with the elimination of water is known as pinacol pinacolone rearrangement.
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

(a) Wittig-Ylide Reaction
Aldehydes and Ketones react with phosphorus Ylides to yield alkenes and triphenylphosphine oxide. An Ylide is a neutral molecule having a negative carbon adjacent to a positive hetero atom. Phosphorus ylides are also called phosphoranes.
(b) Preparation of Ylides
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
(c) Reaction of Ylide with >C=O
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Above things happens in BVO (Bayer Villiger oxidation). Reagents are either per acetic acid or perbenzoic acid or pertrifluoroacetic acid or permonosulphuric acid.
(e) Addition of cyanide
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
(f) Addition of bisulfite:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
In H3O+, RCHO is regenerated because acetals undergo acid catalyzed cleavage much more easily than do ethers. Since acetals are stable in neutral or basic media, they are used to protect the – CH = O group.
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
k) Tischenko reaction:
All aldehydes can be made to undergo the Cannizzaro reaction by treatment with aluminium ethoxide. Under these conditions the acids and alcohols are combined as the ester, and the reaction is then known as the Tischenko reaction; eg, acetaldehyde gives ethyl acetate, and propionaldehyde gives propyl propionate.
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Oxidation of Aldehydes and Ketones
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Tollen’s test chiefly used for the detection of aldehydes.
Tollen’s reagent doesnot attack carbon-carbon double bonds.
c) Strong Oxidants: Ketones resist mild oxidation, but with strong oxidants at high temperature they undergo cleavage of C – C bonds on either sides of the carbonyl group.
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
d)   Haloform Reaction
CH3COR   are readily oxidised by NaOI (NaOH + I2) to iodoform, CHI3, and RCO2Na
Example:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

  • Reduction:

a)  Reduction to alcohols
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Carboxylic Acids:

Carboxylic Acids
Common Names
HCOOH    
Formic acid 
CH3COOH 
Acetic acid 
CH3–CH2–COOH 
Propionic acid 
CH3(CH2)COOH 
Butyric acid 
CH3(CH2)3COOH 
Valeric acid 
CH3(CH2)14COOH 
Palmitic acid 
CH3(CH2)16COOH
Stearic Acid

Physical Properties of Carboxylic Acids

  • The first three acids are colourless, pungent smelling liquids.
  • First four members are miscible in water due the intermolecular hydrogen bonding whereas higher members are miscible in non – polar solvents like ether.
  • Benzene or ethanol but immiscible in water due to the increase in the size of lyophobic alkyl chain.
  • The b.p. of carboxylic acids are higher than alcohols because carboxylic acids exist as dimers due to the presence of intermolecular H-bonding
  • Increase in the number of Halogen atoms on a-position increases the acidity, eg.
    CCl3COOH > CHCl2COOH > ClCH2COOH > CH3COOH
  • Increase in the distance of Halogen from COOH decreases the acidity e.g
    CH3 – CH2 – CH(Cl) – COOH > CH3 – CH(Cl) – CH2 – COOH > CH– CH2 – CH– COOH           
  • Increase in the electro negativity of halogen increases the acidity.
    FCH2COOH > BrCH2COOH > ICH2COOH

Methods of Preparations of Carboxylic Acids
a. Oxidation of Aldehydes & Ketones
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Chemical Reactions of Carboxylic Acids
a. Salt formation:
2CH3COOH + 2Na → 2CH3COO–Na+ + H2
CH3COOH + NaOH → CH3COO–Na+ + H2O
CH3COOH + NaHCO3 → CH3COO–Na+ + H2O + CO2
b. Conversion into Acid Chlorides:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Esters
a) Transesterification :
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
c) Reduction:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Acid Chlorides:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
c) Conversion of Acid Chlorides into Acid Derivatives:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

Amides
a. Hydrolysis:
Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8
b. Acidic Character of Amides:
2RCONH+ HgO → (RCONH)2Hg + H2O
c. Basic Character of Amides:
Amides are very feebly basic and form unstable salts with strong inorganic acids. e.g. RCONH2HCl. The structure of these salts may be I or IIAldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

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FAQs on Aldehydes, Ketones & Carboxylic Acids Class 12 Notes Chemistry Chapter 8

1. What are the common properties of aldehydes, ketones, and carboxylic acids?
Ans. Aldehydes, ketones, and carboxylic acids are all organic compounds that contain a carbonyl group (-C=O). They differ in the arrangement of atoms attached to the carbonyl carbon. Aldehydes have a hydrogen atom attached to the carbonyl carbon, ketones have two alkyl or aryl groups attached, and carboxylic acids have a hydroxyl group (-OH) attached to the carbonyl carbon. They all exhibit some common properties such as being polar due to the presence of the carbonyl group, having higher boiling points compared to hydrocarbons of similar molecular weight, and being soluble in polar solvents.
2. How are aldehydes and ketones named?
Ans. Aldehydes are named by replacing the -e ending of the corresponding parent alkane with -al. The longest continuous carbon chain containing the carbonyl group is numbered, and the carbon atom of the carbonyl group is assigned the lowest possible number. Ketones, on the other hand, are named by replacing the -e ending of the corresponding parent alkane with -one. The longest continuous carbon chain containing the carbonyl group is numbered, and the carbon atom of the carbonyl group is assigned the lowest possible number. If there are multiple carbonyl groups, they are indicated by using numerical prefixes such as di-, tri-, etc.
3. What are some common uses of carboxylic acids?
Ans. Carboxylic acids have a wide range of applications. Some common uses include their use as food preservatives, flavoring agents, and acidifying agents in the food industry. They are also used in the production of pharmaceuticals, dyes, and polymers. Carboxylic acids are often used as solvents for various reactions and as intermediates in the synthesis of other compounds. They are also important components of biological systems, playing vital roles in metabolic processes and as signaling molecules.
4. How do aldehydes and ketones react with nucleophiles?
Ans. Aldehydes and ketones can undergo nucleophilic addition reactions with various nucleophiles. The nucleophile attacks the electrophilic carbon of the carbonyl group, leading to the formation of a new bond and the creation of an intermediate. This intermediate can then undergo further reactions, such as protonation or elimination, to yield different products. The nucleophilic addition reactions of aldehydes and ketones are important in organic synthesis, as they allow the introduction of new functional groups and the formation of more complex molecules.
5. What is the difference between a primary, secondary, and tertiary alcohol?
Ans. The difference between primary, secondary, and tertiary alcohols lies in the number of carbon atoms attached to the carbon atom bearing the hydroxyl group. A primary alcohol has one carbon atom attached to the carbon bearing the hydroxyl group, a secondary alcohol has two carbon atoms attached, and a tertiary alcohol has three carbon atoms attached. This classification is important as it affects the reactivity of alcohols. Primary alcohols are more reactive than secondary alcohols, which are in turn more reactive than tertiary alcohols, due to the ease of access to the hydroxyl group by reactants or reagents.
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