ORGANIC CHEMISTRY1

ORGANIC CHEMISTRY

1. Tetravalency of Carbon

Carbon is a unique element capable of forming four covalent bonds with other atoms. This property is known as tetravalency. Carbon has an atomic number of 6 with electronic configuration 2,4, meaning it has four electrons in its outer shell.

Because carbon requires four more electrons to achieve stability, it forms four covalent bonds with other atoms such as hydrogen, oxygen, nitrogen or other carbon atoms.

Methane Structure (CH₄)

2. Homologous Series

A homologous series is a group of organic compounds with similar chemical properties, the same functional group, and successive members differing by CH₂.

Series	General Formula	Functional Group	Example
Alkanes	CnH₂n+2	Single bond	Methane
Alkanols	CnH₂n+1OH	-OH	Ethanol
Alkanals	CnH₂nO	-CHO	Ethanal
Alkanones	CnH₂nO	-CO-	Propanone
Alkanoic acids	CnH₂nO₂	-COOH	Ethanoic acid

3. IUPAC Nomenclature

The IUPAC system provides a standardized method of naming organic compounds.

Steps in Naming

• Identify the longest carbon chain.
• Number the chain from the end nearest to the functional group.
• Identify substituents and their positions.
• Use appropriate suffix for the functional group.

Examples

Formula	Name
CH₄	Methane
C₂H₆	Ethane
C₂H₅OH	Ethanol
CH₃CHO	Ethanal
CH₃COOH	Ethanoic Acid

4. Physical Properties of Hydrocarbons

• Generally insoluble in water.
• Soluble in organic solvents.
• Boiling point increases with molecular mass.
• Lower members are gases while higher members are liquids or solids.

5. Chemical Properties of Hydrocarbons

• Combustion: Hydrocarbons burn in oxygen to produce carbon dioxide and water.
• Substitution: Hydrogen atoms may be replaced by other atoms.
• Addition: Unsaturated hydrocarbons add atoms across double bonds.
• Cracking: Large molecules break into smaller molecules.

6. Alkanols (Alcohols)

Alkanols contain the -OH functional group. Example: Ethanol (C₂H₅OH)

Ethanol Structure

CH₃ — CH₂ — OH

Uses

• Fuel
• Solvent
• Antiseptic

7. Alkanals (Aldehydes)

Alkanals contain the -CHO functional group. Example: Ethanal.

CH₃ — CHO

Uses

• Preservatives
• Manufacturing chemicals

8. Alkanones (Ketones)

Alkanones contain a carbonyl group between two carbon atoms. Example: Propanone.

CH₃ — CO — CH₃

Uses

• Solvents
• Industrial chemicals

9. Alkanoic Acids

Alkanoic acids contain the -COOH functional group. Example: Ethanoic acid (vinegar).

CH₃ — COOH

Properties

• Weak acids
• React with metals to produce hydrogen gas
• React with alcohols to form esters

10. Derivatives of Alkanoic Acids

• Esters – formed from alcohols and acids
• Amides – formed with ammonia
• Acid chlorides
• Anhydrides

Example ester formation:

Ethanoic acid + Ethanol → Ethyl ethanoate + Water