Introduction to Aldehydes and Ketones

Aldehydes and ketones are organic compounds belonging to the carbonyl family, characterized by the highly reactive carbonyl group (C=O). This group influences both reactivity and physical behavior, making aldehydes and ketones essential in organic chemistry, biological systems, and industries.

The Carbonyl Functional Group

The carbonyl group (C=O) consists of a carbon atom double bonded to oxygen. It is:

Planar in geometry with bond angles ≈ 120°
Polar due to electronegativity difference between C and O
A key site for nucleophilic and electrophilic reactions

What are Aldehydes?

Aldehydes contain the carbonyl group at the end of a carbon chain, bonded to at least one hydrogen atom.

General Formula: R–CHO
Examples: Formaldehyde (HCHO), Acetaldehyde (CH₃CHO)

They occur in essential oils, flavors, perfumes, and metabolic intermediates like glucose.

What are Ketones?

Ketones feature the carbonyl group bonded to two carbon atoms within the chain.

General Formula: R–CO–R′
Examples: Acetone (CH₃COCH₃), Butanone (CH₃COC₂H₅)

Ketones are used as solvents, in fragrances, and as intermediates in metabolism and industries.

Reactivity & Applications

Undergo nucleophilic addition reactions due to polar carbonyl group
Intermediates in synthesis of alcohols, acids, and other compounds
Important in pharmaceuticals, polymers, and dyes
Found in natural biomolecules like sugars (glucose & fructose)

Summary

Aldehydes: R–CHO → terminal carbonyl group
Ketones: R–CO–R′ → internal carbonyl group
Contain polar C=O group affecting physical & chemical properties
Industrial + biological importance

MCQ Quiz – Aldehydes & Ketones

The functional group in aldehydes is:
a) –COOH
b) –CHO ✅
c) –OH
d) –COOR
Which of the following is a ketone?
a) Formaldehyde
b) Acetone ✅
c) Methanol
d) Ethanal
Aldehydes and ketones mainly undergo:
a) Substitution
b) Nucleophilic addition ✅
c) Elimination
d) Polymerization

True/False

Carbonyl group is polar. ✅ (True)
Ketones always have a hydrogen attached to the carbonyl carbon. ❌ (False)
Aldehydes and ketones are important in industrial chemistry. ✅ (True)

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