Aldehyde, ketone or carboxylic Acids is one of the most important topics from CBSE examination & IIT-JEE point of view. Sp, make sure that you go through these important notes to score the most.
Aldehyde and Ketones
Preparation of Aldehydes
a. Oxidation of primary alcohols
Preparation of Ketones
a) Oxidation of Secondary alcohols:
ALSO READ :-
d) With Organometallics
Reactions of Aldehydes and Ketones
a) Aldol condensation
Aldehydes and ketones having alpha hydrogen atom:
ALSO READ :-
b) Cannizzaro reaction:
Aldehydes and ketones having no alpha hydrogen atom:
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.
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.
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.
ALSO READ :-
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.
a) Wittig-Ylide Reaction
Aldehydes and Ketones react with phosphorus Ylides to yield alkenes and triphenyl phosphine oxide. An Ylide is a neutral molecule having a negative carbon adjacent to a positive hetero atom. Phosphorus ylides are also called phosphoranes.
Preparation of Ylides
Reaction of Ylide with >C=O
Above things happens in BVO (Bayer Villiger oxidation). Reagents are either per acetic acid or perbenzoic acid or pertrifluoroacetic acid or permonosulphuric acid.
MUST READ :-
e) Addition of cyanide
f) Addition of bisulfite:
h) Addition of Alcohols; Acetal Formation
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.
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.
Oxidation of Aldehydes and Ketones
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.
d) Haloform Reaction: CH3COR are readily oxidised by NaOI (NaOH + I2) to iodoform, CHI3, and RCO2Na
a) Reduction to alcohols
|Carboxylic Acids||Common Names|
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 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 > CH2 – CH2 – CH2 – 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
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:
a) Transesterification :
c) Conversion of Acid Chlorides into Acid Derivatives:
b. Acidic Character of Amides:
2RCONH2 + 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 II
JEE Mains Crash Course offered by Eckovation
To prepare for the JEE main Exam, one needs a platform where all their problems should be solved with clear concepts. At Eckovation, you will find the following:
1. Chapter wise Notes
2. Chapter wise Practice Papers
3. Mock Tests
4. All India Test Series
5. Chapter wise Video Lectures
6.All India Test Series
8. Peer Discussion
To Join the crash course and study with IIT Delhi Graduates: Click Here