3-10. ETHERS
An ether can be thought of as a hydrocarbon derivative of water where the two
hydrogens of water are replaced by hydrocarbon groups. Thus, ethers have the general
structural formula R-O-R' where R and R' represent any two hydrocarbons, which may
be alike or different. Some examples of ethers are:
CH3-CH2-O-CH2-CH3
-O-CH3
CH2=CH-O-CH3
a. Properties of Ethers. Ether molecules are slightly polar, but cannot form
hydrogen bonds with each other since they do not have a hydrogen atom attached
directly to an oxygen atom. Therefore, they have about the same boiling points and
melting points as alkanes of similar molecular weights.
M.W.
Boiling Point
980C
CH3-CH2-CH2-CH2-CH2-CH2-CH3
100
1000C
CH3-O-CH2-CH2-CH2-CH2-CH3
102
b. Reactions of Ethers. Since ether molecules are slightly polar and have an
oxygen atom in their structure, they can form hydrogen bonds with water. This property
accounts for the fact that ethers are slightly soluble in water. Chemically, ethers are
inert except for the oxidation reaction. Ethers are oxidized in the presence of oxygen to
form peroxides, which are explosive when concentrated.
c. Uses of Ethers. Medicinally, ethers are used as general anesthetics. They
are also used as solvents. Many of you are involved with ordering and storing ethers.
3-11. AMINES
Amines result from the replacement of one or more of the hydrogen atoms of
ammonia with hydrocarbons and have the general formula R-NH2. There are four
classifications of amines: primary, secondary, tertiary, and quaternary. Primary amines
result from replacing one of the hydrogens of ammonia by a hydrocarbon, as in CH3-
NH2; secondary amines result from the replacement of two hydrogens of ammonia by
two hydrocarbons, as in CH3-NH-CH3; and tertiary amines result from the replacement
of all three hydrogens of ammonia by hydrocarbon groups. The fourth classification of
amines is sometimes encountered in drug structures. This classification is the
quaternary amine that is formed by replacing the four hydrogens of the ammonium ion
(NH4 +) by hydrocarbon groups. Whenever one of the hydrocarbon groups connected
to the nitrogen atom contains a benzene ring, the compound is referred to as an
aromatic hydrocarbon.
a. Properties of Amines. The low-molecular-weight amines are all volatile
liquids, and those having up to five carbons are soluble in water. The element nitrogen
is in the same period of the periodic table as oxygen and has some similar properties--
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