Introduction

Alcohols are fundamental organic compounds characterized by the presence of a hydroxyl group (-OH) attached to a saturated carbon atom. Understanding their structure and properties is crucial for HSC Chemistry students, as these compounds play vital roles in both laboratory and industrial applications.

Molecular Structure

The Hydroxyl Group

The defining feature of alcohols is the hydroxyl group (-OH) bonded to a sp³ hybridized carbon atom. This structural arrangement gives alcohols their unique chemical and physical properties.

Classification of Alcohols

Alcohols are classified into three categories based on the number of carbon atoms bonded to the carbon bearing the hydroxyl group:

Nomenclature

Alcohols follow IUPAC nomenclature rules with specific considerations:

For example:

Physical Properties

Intermolecular Forces

Alcohols exhibit three types of intermolecular forces:

The hydroxyl group enables hydrogen bonding, which significantly influences physical properties:

${R-O-H...O-H-R}$

Solubility

Solubility in water depends on two factors:

Smaller alcohols (C1-C3) are completely water-soluble due to the dominance of the hydroxyl group's effects. Solubility decreases as the carbon chain length increases, with C7 and higher alcohols being essentially insoluble.

Boiling Points

Alcohol boiling points are higher than corresponding alkanes due to hydrogen bonding. The relationship between structure and boiling point follows these patterns:

Comparison of Common Alcohols

Alcohol	Formula	Molar Mass (g/mol)	Boiling Point (°C)
Methanol	CH₃OH	32	64.7
Ethanol	C₂H₅OH	46	78.3
1-propanol	C₃H₇OH	60	97.2
2-propanol	C₃H₇OH	60	82.3
1-butanol	C₄H₉OH	74	118.0
2-butanol	C₄H₉OH	74	98.0