The document discusses the nomenclature and structural properties of aldehydes, ketones, and carboxylic acids, highlighting their sp2 hybridization and polar carbonyl group. It also outlines various methods for preparing aldehydes and ketones, including oxidation of alcohols and reactions involving acyl chlorides, nitriles, and hydrocarbons. Additionally, it covers the physical properties, such as boiling points and solubility trends, which influence their use in perfumes and flavoring agents.

1. ALDEHYDES, KETONES
AND
CARBOXYLIC ACIDS

2. Nomenclature
• Common names

3. IUPAC Name

5. Structure of the Carbonyl Group
• Hybridisation: sp2
• Shape: trigonal planar
• Bond angle: 120
• The carbon-oxygen double bond is polarised due to higher
electronegativity of oxygen relative to carbon.
• Hence, the carbonyl carbon is an electrophilic (Lewis acid), and
carbonyl oxygen, a nucleophilic (Lewis base) centre.
• The high polarity of the carbonyl group is explained on the basis of
resonance involving a neutral (A) and a dipolar (B) structures as
shown.

6. Preparation of Aldehydes and Ketones
1. By oxidation of alcohols
2. By dehydrogenation of alcohols

7. 3. From hydrocarbons
(i) By ozonolysis of alkenes:
(ii) By hydration of alkynes:

8. Preparation of Aldehydes
• 1. From acyl chloride (Rosenmund reduction)
• 2. From nitriles and esters
: Stephen
reaction

9. 3. From hydrocarbons
(i) By oxidation of methylbenzene
(ii) (a) Use of chromyl chloride (CrO2Cl2):
This reaction is called Etard reaction.
(b) Use of chromic oxide (CrO3):
benzylidene diacetate

10. (ii) By side chain chlorination followed by hydrolysis
(iii) By Gatterman – Koch reaction

11. Preparation of Ketones
• Treatment of acyl chlorides with dialkylcadmium, prepared by the reaction of
cadmium chloride with Grignard reagent, gives ketones.

12. 2. From nitriles
3. From benzene or substituted benzenes (Friedel-Crafts acylation
reaction)

14. Physical Properties
• The boiling points of aldehydes and ketones are higher than hydrocarbons and ethers
of comparable molecular masses. It is due to weak molecular association in
aldehydes and ketones arising out of the dipole-dipole interactions.
• Their boiling points are lower than those of alcohols of similar molecular masses due
to absence of intermolecular hydrogen bonding.
• The solubility of aldehydes and ketones decreases rapidly on increasing the length of
alkyl chain.
• All aldehydes and ketones are fairly soluble in organic solvents like benzene, ether,
methanol, chloroform, etc.
• Higher aldehydes and ketones are used in the blending of perfumes and flavouring
agents due to their fragrance.