Ch08Loudon7eEDLf21 - Tagged

Chapter 8: Nomenclature and Noncovalent Intermolecular Interactions

  • Source: Loudon and Parise, Organic Chemistry 7e, ©2021, W.H. Freeman and Company

Overview of Chapter 8

  • 8.1 Definitions and Classification of Alkyl Halides, Alcohols, Thiols, Ethers, and Sulfides

  • 8.2 Nomenclature of Alkyl Halides, Alcohols, Thiols, Ethers, and Sulfides

  • 8.3 Structures of Alkyl Halides, Alcohols, Thiols, Ethers, and Sulfides

  • 8.4 Noncovalent Intermolecular Interactions: Introduction

  • 8.5 Homogeneous Noncovalent Intermolecular Attractions: Boiling Points and Melting Points

  • 8.6 Heterogeneous Intermolecular Interactions: Solutions and Solubility

  • 8.7 Applications of Solubility and Solvation Principles

  • 8.8 Summary of Noncovalent Intermolecular Attractions

Alkyl Halides

  • Definition: Compounds where a halogen (F, Cl, Br, I) is bound to a carbon of an alkyl group.

Alcohols and Thiols

  • Alcohol: Characterized by a hydroxy group (—OH) attached to an alkyl group.

  • Thiol: Contains a mercapto group (—SH) attached to an alkyl group.

Differences in Structure

  • Phenols: OH group bonded to the carbon of an aryl group.

  • Enols: OH group bonded to an sp2-hybridized carbon part of a double bond.

Ethers and Sulfides

  • Ethers: Compounds where an oxygen atom is bound to two carbon groups.

  • Sulfides/Thioethers: Sulfur analogs of ethers.

Classification of Compounds

  • Alpha Carbon: The carbon atom connected to a halogen in alkyl halides or an oxygen in alcohols.

  • Classification by Alkyl Groups: Alkyl halides and alcohols are classified based on the number of alkyl groups attached to the alpha carbon.

Nomenclature of Alkyl Halides

  • Common Naming: Alkyl group name followed by the halide name.

  • IUPAC Naming: Halogens are treated as substituents with prefixes: fluoro, chloro, bromo, and iodo.

Nomenclature of Alcohols

  • Specify the alkyl group attached to the —OH group followed by the term alcohol.

Nomenclature of Glycols and Thiols

  • Glycols: Compounds with two or more hydroxy groups on different carbons.

  • Thiols: Named as mercaptans in the common system.

Substitutive Nomenclature

  • The principal group (—OH or —SH) serves as the suffix for the name, with rules and priorities outlined in further detail.

Steps for Naming Compounds

  1. Identify the principal group.

  2. Determine the principal chain based on criteria such as the greatest number of principal groups and bonds.

  3. Number the principal chain to give the lowest numbers to principal groups and substituents.

  4. Construct the name starting with the hydrocarbon name, followed by the principal groups and substituents.

  • Multiple —OH Groups: For more than one —OH group, use the terms diol, triol, etc.

Bond Angles and Lengths

  • α-Carbons: Typically sp3-hybridized with tetrahedral angles.

  • Oxygen: Sp2-hybridized with adjusted bond angles due to lone pairs.

  • Sulfur: Closer to 90° due to its structure and bonding.

Noncovalent Interactions

  • Noncovalent interactions include various forces such as van der Waals forces, hydrogen bonding, and dipole interactions.

  • These interactions are crucial for the stability of biological structures like DNA and proteins.

Boiling Points and Molecular Size

  • Boiling Point Trends: Increases with molecular size and is affected by the structure (branched vs. unbranched).

  • Induced Dipoles: Van der Waals forces can create temporary dipoles that influence boiling points.

Polarizability Factors

  • Polarizability: More polarizable compounds generally have stronger intermolecular attractions.

  • The relationship between electronegativity and polarizability is noted; e.g., iodine is more polarizable than fluorine.

Summary of Noncovalent Intermolecular Attractions

  1. Hydrogen bonding: Strong attractions leading to higher boiling points.

  2. Dipole-Dipole attractions: Permanent dipoles enhance intermolecular attractions.

  3. Van der Waals forces: Influence boiling points based on molecular surface area and shape.

Applications in Chemistry

  • Understanding these interactions aids in predicting solubility and reactivity in various chemical contexts, including solutions and cell membranes, and is important for drug development.