Lecture: Alcohols and Phenols

Overview

This lecture focuses on the chemistry, properties, and reactions of alcohols and phenols. These two classes of organic compounds are important in both biological processes and industrial applications.

Alcohols

Structure and Classification

• General Formula: R-OH
• Primary (1°) Alcohols: The OH group is attached to a carbon atom that is bonded to only one other carbon.
• Secondary (2°) Alcohols: The OH group is attached to a carbon atom bonded to two other carbons.
• Tertiary (3°) Alcohols: The OH group is attached to a carbon atom bonded to three other carbons.

Physical Properties

• Boiling Points: Higher than analogous alkanes due to hydrogen bonding.
• Solubility: Soluble in water; solubility decreases as the carbon chain length increases.

Reactions

• Dehydration: Formation of alkenes by removal of water.
• Oxidation:
  • Primary alcohols yield aldehydes/ketones and can further oxidize to carboxylic acids.
  • Secondary alcohols oxidize to ketones.
  • Tertiary alcohols resist oxidation.

Industrial and Biological Importance

• Used as solvents, antifreeze, and in the synthesis of other compounds.
• Ethanol is notable for its use in alcoholic beverages and as a biofuel.

Phenols

Structure

• General Formula: Ar-OH, where Ar is an aromatic ring.
• Phenols have an OH group attached directly to an aromatic hydrocarbon group.

Physical Properties

• Acidity: More acidic than alcohols due to resonance stabilization of the phenoxide ion.
• Boiling and Melting Points: Generally higher than alcohols due to the stronger hydrogen bonding.

Reactions

• Electrophilic Aromatic Substitution: Phenols undergo reactions such as nitration, halogenation, and sulfonation more readily than benzene.
• Oxidation: Phenols can be oxidized to quinones, which are important in biological systems.

Applications

• Used in the production of plastics, pharmaceuticals, and as antiseptics.
• Example: Aspirin (acetylsalicylic acid) is derived from salicylic acid, a phenol.

Summary

• Alcohols and phenols are diverse in their applications and chemical behavior.
• Understanding their properties and reactions is essential for their effective use in various fields.
• The lecture covered classification, physical properties, major reactions, and differences between alcohols and phenols.