Introduction

Alcohols are versatile organic compounds that undergo three primary types of reactions: dehydration, substitution, and oxidation. Each reaction type produces distinct products under specific conditions, making them fundamental in organic synthesis and industrial processes.

Dehydration of Alcohols

Dehydration is an elimination reaction where alcohols lose a water molecule to form alkenes. This reaction requires:

The general reaction can be represented as:

$\text{R-CH}_2\text{-CH}_2\text{-OH} \xrightarrow{\text{H}^+, \Delta} \text{R-CH=CH}_2 + \text{H}_2\text{O}$

Zaitsev's Rule

When dehydrating secondary or tertiary alcohols, multiple alkene products are possible. Zaitsev's rule predicts that the major product will be the more substituted alkene. For example:

$\text{CH}_3\text{-CH}_2\text{-CHOH-CH}_3 \\\xrightarrow{\text{H}^+, \Delta} \text{CH}_3\text{-CH=CH-CH}_3 \text{ (major)} + \text{CH}_2\text{=CH-CH}_2\text{-CH}_3 \text{ (minor)}$

Substitution with Hydrogen Halides

Alcohols undergo substitution reactions with hydrogen halides (HX) to form alkyl halides. The general reaction is:

$\text{R-OH} + \text{HX} \rightarrow \text{R-X} + \text{H}_2\text{O}$

where X = Cl, Br, or I

Key points:

Oxidation of Alcohols

The oxidation of alcohols depends on their classification:

Primary Alcohols

Primary alcohols can undergo two stages of oxidation:

Secondary Alcohols

Secondary alcohols oxidize to ketones: $\text{R}_2\text{CHOH} \xrightarrow{[\text{O}]} \text{R}_2\text{CO} + \text{H}_2\text{O}$

Tertiary Alcohols

Tertiary alcohols do not undergo oxidation under normal conditions.

Oxidizing Agents

Strong Oxidizing Agents:

Weak Oxidizing Agents: