Download Alcohols, Phenols, Thiols, and Ethers

Alcohols, Phenols,
Thiols, and Ethers
Dr. Michael P. Gillespie
Introduction
• The characteristic functional group of alcohols and
phenols is the hydroxyl group (-OH).
• Alcohols have the general structure R-OH, in
which R is any alkyl group.
• Phenols have the general structure R-OH, in which
R is an aryl group.
• They are substituted water molecules in which
one of the hydrogen atoms has been replaced by
either an alkyl group or an aryl group.
Introduction
• Ethers have two alkyl or aryl groups attached
to the oxygen atom.
• Thiols contain the sulfhydryl group (-SH).
• Many important biological molecules,
including carbohydrates, lipids, and proteins,
contain hydroxyl and/or thiol groups.
Alcohols: Structure &
Properties
• Alcohols are characterized by the hydroxyl
group (-OH).
• They have the general formula R-OH.
• The hydroxyl group is polar; therefore,
alcohols are polar and form hydrogen bonds.
This gives them higher boiling points.
• Smaller alcohols are very water soluble.
Alcohols
Medically Important Alcohols
• Methanol is a toxic alcohol that is used as a
solvent.
• Ethanol is the alcohol consumed in beer, wine, and
distilled liquors.
• Isopropanol is used as a disinfectant.
• Ethylene glycol is used as antifreeze.
• Glycerol is used in cosmetics and pharmaceuticals.
Classification of Alcohols
• Alcohols can be classified as primary,
secondary, or tertiary depending upon the
number of alkyl groups attached to the
carbinol carbon (the carbon bearing the
hydroxyl group).
Preparation of Alcohols
• Alcohols can be prepared by the hydration of
alkenes or the reduction of aldehydes and
ketones.
Dehydration of Alcohols
• Dehydration of alcohols produces alkenes.
Dehydration of Alcohols
Oxidation Reactions
• Primary alcohols undergo oxidation reactions
to produce aldehydes.
• Secondary alcohols undergo oxidation
reactions to produce ketones.
• Tertiary alcohols do not undergo oxidation.
Oxidation of Alcohols
Oxidation & Reduction in
Living Systems
• In organic and biological systems, oxidation
involves the gain or loss of hydrogen.
• Reduction involves the loss of oxygen or gain
of hydrogen.
• Nicotinamide adenine dinucleotide, NAD+, is a
coenzyme involved in many biological
oxidation and reduction reactions.
Phenols
• Phenols are compounds in which the hydroxyl
group is attached to a benzene ring.
• The have the general formula Ar-OH.
• Many phenols are important as antiseptics and
disinfectants.
Phenol
Ethers
• Ethers are characterized by the R-O-R
functional group.
• They are generally non-reactive, but are
extremely flammable.
• Diethyl ether was the first general antiseptic
used in medicine. It has been replaced by
Penthrane and Enthrane, which are less
flammable.
Ether
Thiols
• Thiols are characterized by the sulfhydryl
group (-SH).
• The amino acid cycteine is a thiol that is
extremely important for maintaining the
correct shapes of proteins.
• Coenzyme A is a thiol that serves as a carrier of
acetyl groups in biochemical reactions.
Thiols