chem_232_Wade_9e_chapter_10_ppt_slides_fall_2023_2_

Introduction

  • Instructor: Chad Snyder, PhD, Grace College

  • Topic: Structure and Synthesis of Alcohols, Organic Chemistry, 9th Edition, L. G. Wade, Jr.

  • Year Published: 2017

Overview of Alcohols

  • Alcohols are organic compounds that contain hydroxyl (OH) groups.

  • Importance: Widely used in nature, industry, and in household products.

Structure of Water and Methanol

  • Hybridization: Oxygen is sp3 hybridized, forming a tetrahedral structure.

  • Angles:

    • H—O—H angle in water: 104.5°.

    • C—O—H angle in methyl alcohol (methanol): 108.9°.

  • Carbinol Carbon: Refers to the carbon atom that is bonded to the hydroxyl group.

Classification of Alcohols

  • Primary Alcohol: The carbon bonded to the —OH group is attached to one other carbon.

  • Secondary Alcohol: The carbon with —OH is connected to two other carbons.

  • Tertiary Alcohol: The carbon with —OH is bonded to three other carbons.

  • Aromatic (Phenol): The hydroxyl group is attached to a benzene ring.

Examples of Alcohol Classifications

  • Primary: CH3-CH2-CH2OH (1-Propanol)

  • Secondary: CH3-CHOH-CH2-CH3 (2-Butanol)

IUPAC Nomenclature of Alcohols

  • Steps:

    1. Identify the longest carbon chain containing the —OH group.

    2. Modify the alkane name by dropping the -e and adding -ol.

    3. Number the chain to provide the lowest number to the —OH group.

    4. Number substituents and list them alphabetically.

Examples of IUPAC Nomenclature

  • Types of Alcohols and Examples:

  • Primary: Ethanol (ethyl alcohol)

  • Secondary: 2-Methylpropan-1-ol (Isobutyl alcohol)

  • Tertiary: 2-Methylpropan-2-ol (tert-Butyl alcohol)

Alkenols (Enols)

  • Hydroxyl group has precedence in naming; assign lowest number to the carbon with —OH.

  • Use the suffix -ene before -ol.

  • Example: pent-4-ene-2-ol

Priority of Functional Groups (Naming)

  • Highest to lowest priority:

    • Acids

    • Esters

    • Aldehydes

    • Ketones

    • Alcohols

    • Amines

    • Alkenes, Alkynes

    • Alkanes

    • Ethers

    • Halides

Hydroxy Substituent

  • When the —OH group is part of a higher priority compound, it is named as hydroxy.

  • Example: 4-hydroxybutanoic acid (gamma-hydroxybutyric acid, GHB)

Common Names for Alcohols

  • Alcohols can be named as alkyl alcohols but generally for smaller groups.

    • Examples: Isobutyl alcohol (2-methylpropan-1-ol), sec-butyl alcohol (butan-2-ol)

Naming Diols

  • Diols: Two hydroxyl groups require two locational numbers.

  • Suffix -diol is used.

  • Example: Hexane-1,6-diol

Glycols

  • 1,2-diols are referred to as glycols; commonly named using the alkenes they derive from.

  • Examples include ethylene glycol (ethane-1,2-diol) and propylene glycol (propane-1,2-diol).

Phenol Nomenclature

  • The —OH group on phenol is assumed to be on carbon 1.

  • Use ortho-, meta-, and para- for di-substituted phenols.

  • Example: 3-chlorophenol is meta-chlorophenol.

Physical Properties of Alcohols

  • Alcohols generally have higher boiling points than alkanes and ethers due to hydrogen bonding.

  • Miscibility in water: Small alcohols are miscible in water; solubility decreases with increased alkyl group size.

Alcohol Examples and Their Properties

  • Table of Selected Alcohols: Physical Properties

    • Methanol (CH3OH): bp = 65°C, mp = -97°C

    • Ethanol (C2H5OH): bp = 78°C, mp = -114°C

    • Propan-1-ol (C3H7OH): bp = 97°C, mp = -126°C

    • Butan-2-ol (C4H10O): bp = 100°C, mp = -90°C

    • Cyclohexanol: bp = 162°C

Boiling Points of Alcohols

  • Higher boiling points relative to ethers and alkanes due to hydrogen bonding.

  • More energy is required to break hydrogen bonds, which results in higher boiling points.

Methanol

  • Commonly known as wood alcohol.

  • Industrial applications as a solvent; toxic dose: ~100 mL.

  • Used as fuel: low emissions and high octane rating.

Ethanol

  • Produced via fermentation; distillation for liquor production.

  • 95% ethanol = constant boiling azeotrope.

  • Toxic dose: ~200 mL.

Propan-2-ol (Isopropyl Alcohol)

  • Produced by catalytic hydration of propylene.

  • Commonly used as rubbing alcohol.

Acidity of Alcohols

  • pKa range for alcohols: 15.5–18.0.

  • Acidity decreases with increased substitution on alkyl groups; halogens enhance acidity.

  • Example: Phenol is markedly more acidic than cyclohexanol.

Alcohol Reactions and Synthesis

  • Formation of Alkoxide Ions: Reaction of ethanol with sodium metal yields sodium ethoxide.

  • Phenoxide Ion Formation: Aromatic alcohols like phenol exhibit increased acidity.

  • Synthesis Methods: Nucleophilic substitution (SN2) and water addition to double bonds produce alcohols... ...