CHAPTER_12_MOD

Alcohols, Phenols, Thiols, and Ethers

Chapter Overview

• Focus on organic compounds: Alcohols, Phenols, Thiols, Ethers.

Alcohols

• Definition: Organic compounds containing a hydroxyl group (OH).

• Presence: Found in sugars, fats, proteins (e.g., Sucrose, Cholesterol).

Classification of Alcohols

• Types of Alcohols:

  • Primary Alcohol: Contains the hydroxyl group attached to a carbon atom with two hydrogens.

  • Secondary Alcohol: The hydroxyl group is attached to a carbon atom bonded to two other carbon atoms.

  • Tertiary Alcohol: The hydroxyl group's carbon is bonded to three other carbons.

• Examples:

  • Methanol (methyl alcohol)

  • Ethanol (CH3CH2OH)

  • Taxol (used in chemotherapy)

Properties of Alcohols

• Boiling Point:

  • Comparison with alkanes: Alcohols generally have higher boiling points than alkanes due to hydrogen bonding.

  • Example temperatures: Alkanes (-42 °C) vs. alcohols (78 °C).

• Solubility in Water:

  • Alcohols with 1-4 carbon atoms are soluble in water ("Like dissolves like").

  • Presence of hydrogen bonds increases their solubility.

Solubility in Depth

• Octanol vs. other alcohols and solvents like Vitamin C showing solubility behavior.

IUPAC Nomenclature for Alcohols

• Steps to Name Alcohols:

  1. Find the longest continuous carbon chain containing the hydroxyl group.

  2. Number the chain for the lowest possible hydroxyl group number.

  3. Name and order substituents alphabetically.

• Examples:

  • 2,4-dimethylcyclohexanol

  • 6-bromo-2-methyl-2,5-heptanediol

Reactions Involving Alcohols

• Types of Reactions:

  • Hydration: Incorporating water to form alcohol.

  • Intramolecular Dehydration: Elimination reaction yielding alkenes (needs adjacent hydrogen).

Elimination and Zaitsev Rule

• Zaitsev Rule: Major product is the more substituted alkene.

• Example: Showing the dehydration reaction and identifying the major product.

Oxidation of Alcohols

• Transformations: Primary and secondary alcohols can oxidize to aldehydes, ketones, or carboxylic acids by losing two hydrogen atoms.

• Tertiary Alcohols: Do not undergo oxidation due to lack of a hydrogen at the alcohol-bearing carbon.

Phenols

• Definition: Compounds with the hydroxyl group attached to a benzene ring.

• Uses: Common in healthcare for their germicidal, antiseptic, and disinfectant properties.

Ethers

• Properties: More polar than alkanes but less polar than alcohols; higher boiling points than alkanes; lower than alcohols.

IUPAC Nomenclature of Ethers

• Naming: Alkyl groups containing the oxygen are termed alkoxy.

• Example: 3-Ethoxypentane.

Intermolecular Dehydration

• Process: Two alcohols react with acid and heat to form an ether and water.

• Example Reaction: CH3CH2OH + CH3CH2OH ➞ CH3CH2OCH2CH3 + H2O (with acid and heat).

Thiols

• Definition: Compounds containing a sulfhydryl group (-SH); typically have unpleasant odors.

• Examples: 2-butene-1-thiol, 3-methyl-1-butanethiol.

Practice Problems

• Tasks include identifying compounds with the highest boiling points, writing IUPAC names, predicting products, and writing equations for reactions like intermolecular dehydration.