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... ...