23.6 Ethers – Structure and Naming

Learning Objectives

By the end of this section, you will be able to:

  • Describe the structural difference between an alcohol and an ether that affects physical characteristics of each.
  • Name simple ethers.
  • Describe the structure and uses of some ethers.

With the general formula ROR′, an ether may be considered a derivative of water in which both hydrogen atoms are replaced by alkyl or aryl groups (aryl means aromatic). It may also be considered a derivative of an alcohol (ROH) in which the hydrogen atom of the OH group is replaced by a second alkyl or aryl group (Figure 23.6a.).

 

There are three structures: On the left is the general structure of ethers showing an oxygen with an R group on one side and an R' on the other; in the middle is the condensed structure of methoxymethane (dimethyl ether) where a central oxygen has a methyl on either side; and c) ball and stick model of methoxymethane (dimethyl ether)
Figure 23.6a. a) General structure of ethers, b) condensed structure of methoxymethane (dimethyl ether) and c) ball and stick model of methoxymethane (dimethyl ether) (credit left: Image by Hbf878, CC0; middle: Image by B Levin13, CC BY-SA 3.0; right: Image by Benjah-bmm27, PDM)

Naming Ethers

The IUPAC naming process of naming ethers involves separately naming each of the two groups attached to the oxygen atom.

  1. The group that has the longest continuous carbon chain is considered the parent chain and is named accordingly. (For example, if the longest chain consists of 3 carbons, the parent chain would be propane).
  2. The group attached to the oxygen that has the shorter chain is named as an alkoxy group, which replaces the “ane” ending with “oxy”. For example, a one carbon chain would go from methane to methoxy.
  3. Remaining substituents are numbered and named as in previous sections.

Example 23.6a

What is the IUPAC name for each ether?

  1. CH3CH2OCH2CH2CH3
  2. CH3CH2CH2CH2CH2CH2OCH2CH2CH2CH3

Solution:

  1. There is a two carbon group and a three carbon group on either side of the oxygen. The parent chain is based on the longer group (3 carbons = propane) and the alkoxy group is the shorter chain (2 carbons = ethoxy). The compound’s name would be ethoxypropane.
  2. There is a six carbon group and a four carbon group on either side of the oxygen. The parent chain is based on the longer group (6 carbons = hexane) and the alkoxy group is the shorter chain (4 carbons = butoxy). The compound’s name would be butoxyhexane.

Exercise 23.6a

What is the IUPAC name for each ether?

  1. CH3CH2CH2CH2OCH2CH2CH2CH3
  2. the molecular structure of ethoxycyclobutane
    (Credit: Intro Chem: GOB (V. 1.0)., CC BY-NC-SA 3.0.)

     

Check Your Answers:[1]

Simple ethers also have common names, formed from the names of the groups attached to oxygen atom, followed by the generic name ether. If both groups are the same, the group name should be preceded by the prefix di-.

Example 23.6b

What is the common name for each ether?

  1. CH3–O–CH2CH2CH3
  2. CH3–O–CH3
  3. CH3CH2–O–CH2CH3

Solutions:

  1. methyl propyl ether
  2. dimethyl ether
  3. diethyl ether

Exercise 23.6b

What is the common name of this ether?

A molecular structure is shown with a red C H subscript 3 group bonded up and to the right to a red O atom. The O atom is bonded down and to the right to a C H subscript 2 group. The C H subscript 2 group is bonded up and to the right to a C H subscript 3 group.

Check Your Answer:[2]

Source: Exercise 23.6b is adapted from General Chemistry 1 & 2, CC BY 4.0.

Physical Properties

Ether molecules have no hydrogen atom on the oxygen atom (that is, no OH group). Therefore, there is no intermolecular hydrogen bonding between ether molecules.  As a result, ethers have quite low boiling points for a given molar mass. In fact, ethers have boiling points about the same as those of alkanes of comparable molar mass and much lower than those of the corresponding alcohols (Table 23.6a.).

Table 23.6a. Comparison of Boiling Points of Alkanes, Alcohols, and Ethers
Condensed Structural Formula IUPAC Name Common Name Molar Mass Boiling Point (°C) Intermolecular Hydrogen Bonding in Pure Liquid?
CH3CH2CH3 propane propane 44 –42 no
CH3OCH3 methoxymethane dimethyl ether 46 –25 no
CH3CH2OH ethanol ethyl alcohol 46 78 yes
CH3CH2CH2CH2CH3 pentane pentane 72 36 no
CH3CH2OCH2CH3 ethoxyethane diethyl ether 74 35 no
CH3CH2CH2CH2OH butan-1-ol butyl alcohol 74 117 yes

Table source: “14.8: Ethers” In Basics of GOB (Ball et al.), CC BY-NC-SA 4.0.

Ether molecules do have an oxygen atom, however, and engage in hydrogen bonding with water molecules. Consequently, an ether has about the same solubility in water as the alcohol that is isomeric with it. For example, dimethyl ether and ethanol (both having the molecular formula C2H6O) are completely soluble in water, whereas diethyl ether and 1-butanol (both C4H10O) are barely soluble in water (8 g/100 mL of water).

Spotlight on Everyday Chemistry: General Anesthetics

A general anesthetic acts on the brain to produce unconsciousness and a general insensitivity to feeling or pain. Diethyl ether or ethoxyethane (CH3CH2OCH2CH3) was the first general anesthetic to be used. Diethyl ether is a colourless, volatile liquid that is highly flammable.

Oil painting depicting the first use of ether as an anesthetic in 1846 by the dental surgeon W.T.G. Morton
Figure 23.6b. William Morton, a Boston dentist, introduced diethyl ether into surgical practice in 1846. This painting shows an operation in Boston in 1846 in which diethyl ether was used as an anesthetic. Inhalation of ether vapor produces unconsciousness by depressing the activity of the central nervous system. (Image credit: Oil painting (V0018140) by Ernest Board, PDM).

Diethyl ether is relatively safe because there is a fairly wide gap between the dose that produces an effective level of anesthesia and the lethal dose. However, because it is highly flammable and has the added disadvantage of causing nausea, it has been replaced by newer inhalant anesthetics, including the fluorine-containing compounds halothane, enflurane, and isoflurane (Figure 23.6c.). Unfortunately, the safety of these compounds for operating room personnel has been questioned. For example, female operating room workers exposed to halothane suffer a higher rate of miscarriages than women in the general population.

3 compounds from left to right represent three modern, inhalant, halogen-containing, anesthetic compounds (halothane, enflurane, and isoflurane)
Figure 23.6c. These three modern, inhalant, halogen-containing, anesthetic compounds (halothane, enflurane, and isoflurane) are less flammable than diethyl ether. (Credit: Intro Chem: GOB (V. 1.0)., CC BY-NC-SA 3.0.)

Ethers are produced from alcohols as previously described in this chapter.  Figure 23.6d. shows an example of ether production.

This figure shows a reaction that results in diethyl ether. The first molecule, which is labeled, “ethanol,” is a two C atom chain. The first C atom is bonded to three H atoms and a second C atom. The second C atom is bonded to a red O atom with two sets of electron dots. The O atom has a red bond to a red H atom. There is a plus sign. The next molecule, which is labeled, “ethanol,” is a red H atom with a red bond to a red O atom with two pairs of electron dots. The O atom is bonded to a C atom which is bonded to two H atoms and a second C atom. The second C atom is bonded to three H atoms. There is a green dotted box around the red H atom in the first molecule, the plus sign, and the red H and O atoms in the second molecule. To the right o the second molecule there is an arrow labeled H subscript 2 S O subscript 4 above and Greek capital delta below. The arrow is labeled, “sulfuric acid.” The resulting molecules are a C atom bonded with three H atoms and a second C atom. The second C atom is bonded to two H atoms and a red O atom. The red O atom has two sets of electron dots. The O atom is bonded to a third C atom which is bonded to two H atoms and a fourth C atom. The fourth C atom is bonded to three H atoms. This molecule is labeled, “diethyl ether.” There is a plus sign and a red H O H.
Figure 23.6d. Formation of ether from intermolecular dehydration of two alcohol molecules (credit: General Chemistry 1 & 2, CC BY 4.0).

Spotlight on Everyday Chemistry: Foxgloves

Foxgloves are poisonous.  The large biological molecules contained in the flowers have many ether functional groups.  Read more about the chemistry of foxgloves in Infographic 23.6a.

Infographic 23.6a.  Read more about “The Chemistry of Foxgloves – Poison & Medicine” by Andy Brunning / Compound Interest, CC BY-NC-ND, or access a text-based summary of infographic 23.6a [New tab].

Link to Enhanced Learning

For more support with naming ethers and their properties, see Ether naming and introduction (video) | Khan Academy.

Attribution & References

  1. 1) butoxybutane 2) ethoxycyclobutane

    ↵

  2. ethylmethyl ether. (Branches are in alphabetical order.)

    ↵

definition

License

Icon for the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License

Organic and Biochemistry Supplement to Enhanced Introductory College Chemistry Copyright © 2024 by Gregory Anderson; Caryn Fahey; Adrienne Richards; Samantha Sullivan Sauer; David Wegman; and Jen Booth is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

Share This Book