Ethers Epoxides and Thioethersaddresses
the typical topics of structure, nomenclature, physical properties,
preparations, reactions, and chemical analysis. A unit addressing
thioethers is included.
Under Nomenclature, the four important areas are addressed: common
nomenclature, systematic (IUPAC), cyclic, and aromatics. These nomenclature
units are designed to help students transition from one type of
nomenclature to another.
The boiling points and solubilities of ethers stress their ability
to participate in hydrogen bonding, but not generate hydrogen bonding
themselves. Therefore, the low boiling points but high solubilities
in water and alcohols is explained. In this section on physical
properties, the ability of these ethers to form complexes as with
the grignard, is used to explain their widespread use as solvents.
Although crown ethers are mentioned in another unit on phase transfer
catalysts, the structure is appropriately introduced in this unit.
Preparations of ethers involve dehydration of alcohols, the classic
Williamson synthesis, alkoxymercuration followed by demercuration,
and the formation of oxiranes. Whenever it is thought to be helpful
in understanding the mechanism of these reactions, animations of
mechanisms are presented.
Reactions of ethers presents the expected acid cleavage, cleavage
of rings in water and alcohols, ring opening reactions as a version
of acid cleavage, reactions with the grignard, and the all important
section on reaction with oxygen. The dangers of ethers are often
thought to lie in their flammability, and that characteristic is
certainly evident. However, the ability of diethyl ether, among
others, to produce “peroxides” must not be overlooked. This unit
discusses how these hydroperoxides and peroxides are formed as well
as simple analyses to identify their formation. The unit then suggests
a few ways in which hydroperoxide and peroxide formations may be
Spectral analysis of ethers classically involves finding what is not present in the infrared. The knowledge that oxygen is
present and the absence of other, characteristic oxygen signals
suggests the presence of ethers. The characteristic oxonium ion
formation via alpha cleavage is mentioned as possibly present in
the mass spec of ethers. Downfield shifts in HNMR and CMR are also
Thioethers are presented in a separate section within this unit.
Structure of thioethers, nomenclature, preparation, reactions, and
characteristics are addressed. The application of the Williamson
synthesis in the preparation of thioethers serves to reinforce the
versatility, the limitations, and the practicality of this classic.
The ability of thioethers to undergo Sn2 reactions in which they
produce excellent alkylating agents is stressed for its importance
in biochemistry. The unit concludes with comments regarding the
general characteristics of thioethers.