13.2 Characteristic Organic Reactions

1. Types of Organic Compounds and Reactions

1.1 Homologous Series

A homologous series is a group of organic compounds that share three important features:

• They have the same functional group (the reactive part of the molecule)
• They have the same general formula (a mathematical pattern for their molecular formula)
• They have similar chemical properties (they react in similar ways)

Example: Ethanol (C₂H₅OH) and propanol (C₃H₇OH) both belong to the alcohol homologous series. Both have an -OH functional group, both follow the general formula CₙH₂ₙ₊₁OH, and both react in similar ways.

1.2 Saturated and Unsaturated Compounds

Saturated compounds contain only single bonds between carbon atoms. This means every carbon atom is bonded to the maximum possible number of hydrogen atoms.

Example: Butane (C₄H₁₀) is saturated because it has only C-C and C-H single bonds.

Unsaturated compounds contain at least one carbon-carbon double bond (C=C) or triple bond (C≡C). This means not all carbon atoms are bonded to the maximum number of hydrogen atoms.

Example: Butene (C₄H₈) is unsaturated because it has a C=C double bond.

Why does this matter?

• Saturated compounds (like alkanes) are generally less reactive
• Unsaturated compounds (like alkenes) are more reactive because the double bond can break and form new bonds