Plus Two Chemistry Notes Chapter 12 Aldehydes, Ketones and Carboxylic Acids is part of Plus Two Chemistry Notes. Here we have given Plus Two Chemistry Notes Chapter 12 Aldehydes, Ketones and Carboxylic Acids.
|Text Book||NCERT Based|
|Chapter Name||Aldehydes, Ketones and Carboxylic Acids|
|Category||Plus Two Kerala|
Kerala Plus Two Chemistry Notes Chapter 12 Aldehydes, Ketones and Carboxylic Acids
Aldehydes and Ketones
Structure of C = O group
Since +ve charge on carbon atom attracts nucleophile, major reaction of these compounds are nucleophilic reactions.
Nomenclature of Aldehydes and Ketones
The IUPAC name of is
1. From alcohols.
2. From alkenes (ozonolysis).
3. From alkynes.
4. From nitriles (Stephen reaction).
Preparation of aromatic aldehydes and ketones
2.By side chain chlorination and hydrolysis:
3. By Gatterman-Koch reaction:
4. By Rosenmund’s reduction:
5. By Friedel-Crafts acylation:
Nucleophilic addition reactions
Write the structures of products of the following reactions :
Relative Reactivity of Aldehydes and Ketones
Note: As numbers of ‘R’ increases, +ve charge on ‘C’atom decreases, ie, reactivity decreases, (R → + l effect group)
HCHO > R-CHO > R-CO-R ; order of reactivity.
1. Addition of NaHSO3.
2. Addition of Grignard reagent.
Note: por more, refer ‘preparation of aicohols’ in the previous chapter.
3. Addition of alcohols.
4. Addition of Ammonia derivatives
a. Clemmensen reduction:
b. Wolff-Kishner reduction:
7. Aldol condensation
Only aldehydes having atleast one ∝-H can undergo this reaction.
8. Cannizzaro reaction
- Aldehydes without ∝-H undergo this reaction.
- Products are alcohol and acid salt.
The compound that does not undergo Cannizzaro reaction Is
acetaldehyde contains ∝-hydrogens and I hence does not undergo aldol condensation
Test to distinguish between Aldehydes & Ketones
1. Tollen’s test:
Aldehydes+Tollen’s reagent → Silver mirror
CH3-CHO+ 2[Ag(NH3)2]+ + 3OH– → CH3COO– + 2Ag + 2H2O + 4NH3
2. Fehling’s test:
Aldehydes+Fehling’s solution → Brown ppt
H-CHO + 2CU2+ 5OH– → HCOO– + Cu2O + 3H2O (brown ppt)
Why are aldehydes more reactive than ketons?
Aldehydes are more reactive than ketones due to the following reason:
Due to smaller +l -effect of one alkyl group in aldehydes as compared to larger + l-effect of two alkyl groups, the magnitude of positive charge on the carbonyl carbon is more in aldehydes than in ketons. As a result, nucleo-philic addition reactions occur more readily in aldehydes than in ketones.
R-COOH → RCOO- + H+ ∴ AClD
7. Acid chlorides:
The IUPAC name of is
Hell-Volhard- Zelinsky reaction:
∝-H is replaced by Cl,Br in red phosphorus
Ring reactions :
All ring reactions occur at meta position.
Other reactions are:
Compounds with (-CO-CH3-) group react with l2/NaOH to give yellow precipitate (Iodoform).
Also alcohols (-CH3-CO-) group react with l2/NaOH to give yellow precipitate.
eg., (CH3COCH3, CH3CHO, CH3CH2OH) etc.
Test for carboxylic acids:
RCOOH + NaHCO3 → RCOONa + H2O + CO2 ↑
Note: CO2 ↑→ (Brisk effervescence)
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