Lecture 28 - Alcohols Ethers and Epoxides

  • Alcohols, ethers, and epoxides are organic compounds characterized by carbon-oxygen bonds.

9.2 Structure and Bonding

  • Functional Groups: All contain carbon-oxygen σ bonds.

9.3 Alcohols

  • Definition: Hydroxy group (−OH) bonded to an sp3 hybridized carbon.

  • Classification: Based on alkyl groups attached to the carbon bearing −OH.

    • 1° (Primary): One alkyl group.

    • 2° (Secondary): Two alkyl groups.

    • 3° (Tertiary): Three alkyl groups.

9.4 Enols and Phenols

  • Enols: Hydroxy group on a carbon of a C=C double bond, undergo different reactions than alcohols.

  • Phenols: Hydroxy group attached to carbons on a benzene ring, also different reactions than alcohols.

9.5 Ethers

  • Definition: Compounds with two alkyl groups bonded to a single oxygen atom.

    • Symmetrical Ethers: Identical R groups.

    • Unsymmetrical Ethers: Different R groups.

9.6 Epoxides

  • Definition: Ethers with a three-membered ring containing oxygen.

  • Bond Angle: C−O−C bond angle of 60° leads to angle strain and increased reactivity.

9.7 Oxygen Hybridization and Geometry

  • Hybridization: Oxygen in these compounds is sp3 hybridized.

  • Geometry: Bent shape similar to water, with bond angles around O similar to tetrahedral angles (109.5°).

9.8 Electrostatic Potential Maps

  • Visualization of electron-rich regions represented with red coloring around sp3 hybridized O atoms.

9.9 Intermolecular Forces

  • Interactions: Alcohols, ethers, and epoxides exhibit dipole-dipole interactions due to their polar bonds.

  • Hydrogen Bonding: Only alcohols can perform hydrogen bonding, making them more polar compared to ethers and epoxides.

9.10 Physical Properties

  • Boiling and Melting Points: Higher intermolecular forces lead to increased boiling and melting points. Hydrogen bonding enhances boiling points.

9.11 Solubility

  • Water Solubility:

    • Soluble in water with ≤ 5 carbons.

    • Insoluble in water with > 5 carbons due to large alkyl regions.

9.12 Naming Alcohols

  • IUPAC Naming: Find the longest carbon chain with the −OH group, change the suffix to –ol, and number the chain to provide the −OH group the lowest possible number.

  • Common Names: Often used for simpler alcohols, by naming the carbon chain as a single alkyl group followed by 'alcohol'.

9.13 Special Cases

  • Diols and Triols: Compounds with two (diols) or three (triols) hydroxy groups; named accordingly with the suffix –diol or –triol.

9.14 Common Alcohols

  • Methanol: Toxic, known as wood alcohol.

  • Propan-2-ol: Major component of rubbing alcohol, used for cleaning and sterilization.

  • Ethylene glycol: Component of antifreeze, toxic despite sweet taste.

9.15 Ethanol from Corn

  • Ethanol is derived through the hydrolysis of starch and fermentation, a renewable fuel source mixed with hydrocarbons to create usable fuels.

9.16 Common Names and Naming of Ethers

  • Nomenclature: Name alkyl groups attached to oxygen in alphabetical order, include "ether" in the name. For symmetrical ethers the prefix “di-” is used.

9.17 Naming Epoxides

  • Methods: Epoxides can be named as epoxyalkanes, oxiranes, or alkene oxides, with specific rules for each method in designating substituents.

9.18 Interesting Applications

  • Medicinal Applications: Compounds containing epoxides such as eplerenone and tiotropium bromide.