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Properties of Ether

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What is Ether?

Ethers are organic compound classes that contain an ether group, an oxygen atom connected to two aryl or alkyl groups. They do have the general formula as R - O - R′, where R and R′ represent the aryl or alkyl groups. Ethers can be classified further into two varieties. Suppose, if the alkyl groups are the same on both sides of an oxygen atom, then it is known as a simple or symmetrical ether. On the other side, if they are different, ethers are referred to as mixed or unsymmetrical ethers.


A typical example of the first group is solvent and anesthetic diethyl ether simply referred to as "ether" (CH3 - CH2 - O - CH2 - CH3). In organic chemistry, ethers are common and even more prevalent in biochemistry, as they are common linkages in lignin and carbohydrates. The structure of ethers is similar to the structure of alcohol, and both alcohols and ethers are similar in structure to water.


The general formula of ethers can be R-O-R, R-O-Ar, or Ar-O-Ar, where Ar represents an aryl group, and R represents an alkyl group.


Structure of Ether

The C-O-C linkage is characterized by the bond angles of 104.5 degrees, with the C-O distances being about 140 picometres. The ether's oxygen is more electronegative than that of carbons. Therefore, alpha hydrogens are more acidic than in the regular hydrocarbon chains.


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Ether Nomenclature

To name ether, there are two ways. One of the most common ways is to identify the alkyl groups on either side of the oxygen atom in alphabetical order, writing as "ether." For example, ethyl methyl is the one that has an ethyl group and a methyl group on any side of the oxygen atom. If two alkyl groups are identical, the ether is called di (alkyl) ether. And, for suppose, diethyl ether is the one with an ethyl group on each side of the oxygen atom.


The other way of naming is formal by the IUPAC method. Here, the form is short alkyl chain, oxy, and long alkyl chain. As an example, the IUPAC name of ethyl methyl ether would be methoxy ethane.


The stem of the compound is called oxacycloalkane in cyclic ethers. "Oxa" is an indicator of the carbon replacement by oxygen in the ring. Oxacyclopentane is an example of a five-membered ring, where there are four carbon and one oxygen atoms.


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Properties of Ether

Ethers are rather nonpolar because of the presence of an alkyl group on either side of the central oxygen. There exist bulky alkyl groups adjacent to it means the oxygen atom is highly unable to participate in hydrogen bonding. Thus, ethers have lower boiling points when compared to alcohols having the same molecular weight. 


As the ethers alkyl chain becomes longer; however, the difference in boiling points becomes smaller. This happens due to the effect of increased Van der Waals interactions as the number of carbons increases. And thereby, the number of electrons increases as well. The two lone pairs of electrons in the oxygen atoms allows for ethers to form hydrogen bonds reacting with water. Ethers are much more polar than alkenes, whereas it is not as polar as alcohols, esters, or amides of comparable structures.


The physical and chemical properties of ether are given below.

Ether Physical Properties

Ethers physical properties can be described as below.

  • An ether molecule contains a net dipole moment. This can be attributed to the C - O bond polarity.

  • Ether's boiling point is comparable to the alkanes. However, it is very low compared to alcohols of comparable molecular mass. Besides, this is the fact of the polarity of the C-O bond.

  • Ether's miscibility with water resembles those of alcohol.

  • The water molecules of ether are miscible in water. Also, we can attribute this to the fact that like alcohols, the ether's oxygen atom can also form hydrogen bonds with a water molecule.


Ether Chemical Properties

Generally, ethers undergo chemical reactions in two ways. Let us look at it in the section below.


C-O Bond Cleavage

Generally, ethers are very unreactive in nature. When we add an excess hydrogen halide to the ether, cleavage of the C-O bond takes place. It results in the formation of alkyl halides. The order of reactivity is as below.

HI > HBr > HCl

R-O-R + HX → RX + R-OH


Electrophilic Substitution

The ether's alkoxy group activates the aromatic ring at para and ortho positions for electrophilic substitution. Some common electrophilic substitution reactions are Friedel Crafts reaction, halogenation, and a few more.


Ether Halogenation Reaction

Ethers of aromatic type undergo halogenation. For suppose, Bromination - when we add halogen atoms in the presence or absence of a catalyst.


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Friedel Crafts Reaction of Ethers

Aromatic ethers undergo Friedel Crafts reaction. For example, the addition of an acyl or alkyl group when we introduce it to an acyl or alkyl halide in the presence of a Lewis acid as a catalyst.


Substitution of Electrophiles

The alkoxy group of the ether activates the aromatic ring at the para and ortho positions for electrophilic substitution. Friedel Crafts reaction, halogenation, and some others are samples of common electrophilic substitution reactions.


In this article, we discussed the ether and its properties. To know more about the key terms and other related topics of chemistry, you can explore our website. 

FAQs on Properties of Ether

1. What are the main physical properties of ethers as per the Class 12 syllabus?

The key physical properties of ethers are their polarity, boiling point, and solubility.

  • Polarity: Ethers are slightly polar molecules. The C-O-C bond is bent, so the dipole moments of the two C-O bonds do not cancel out, resulting in a net dipole moment.
  • Boiling Point: They have low boiling points, comparable to alkanes of similar mass. This is because ether molecules cannot form intermolecular hydrogen bonds with each other, unlike alcohols.
  • Solubility: Lower ethers are somewhat soluble in water because the oxygen atom can form hydrogen bonds with water molecules. However, solubility decreases as the size of the alkyl groups increases.

2. What are the two main types of chemical reactions that ethers undergo?

Ethers are generally unreactive but undergo two significant types of reactions:

  • Cleavage of the C-O bond: This bond can be broken by reacting the ether with strong mineral acids, particularly hydrogen halides (HI and HBr) at high temperatures. This reaction yields an alkyl halide and an alcohol (or two alkyl halides if the acid is in excess).
  • Electrophilic Substitution: Aromatic ethers, like anisole, undergo electrophilic substitution on the benzene ring. The alkoxy (-OR) group is an activating and ortho-, para-directing group, facilitating reactions like halogenation, Friedel-Crafts reactions, and nitration.

3. Why do ethers have significantly lower boiling points than alcohols of comparable molecular mass?

Ethers have much lower boiling points than alcohols of similar mass because alcohol molecules can form strong intermolecular hydrogen bonds with each other through their hydroxyl (-OH) groups. Ether molecules lack this -OH group and cannot form hydrogen bonds among themselves. The energy required to overcome the weaker van der Waals forces in ethers is much less than the energy needed to break the strong hydrogen bonds in alcohols, resulting in lower boiling points for ethers.

4. How does the bent structure of the ether functional group influence its properties?

The bent structure of the C-O-C functional group is crucial to its properties. The bond angle is approximately 111.7° (in diethyl ether), similar to a tetrahedral angle. This geometry prevents the individual C-O bond dipoles from cancelling each other out, giving the molecule a net dipole moment and making it slightly polar. Furthermore, the lone pairs of electrons on the oxygen atom are sterically accessible, allowing ethers to act as Lewis bases by donating an electron pair to a Lewis acid.

5. Why are ethers like diethyl ether commonly used as solvents in organic reactions?

Ethers, particularly diethyl ether and tetrahydrofuran (THF), are widely used as solvents for several reasons. They are relatively inert and do not react with many reagents, including strong organometallic reagents like Grignard reagents. Their slight polarity allows them to dissolve a wide range of non-polar and moderately polar organic compounds. Their low boiling points also make them easy to remove from a reaction mixture by evaporation after the reaction is complete.

6. If ethers are generally unreactive, why are they highly susceptible to cleavage by strong acids like HI?

While the C-O bond in ethers is stable, their reactivity with strong acids like HI stems from the ether's ability to act as a Lewis base. The oxygen atom's lone electron pairs readily accept a proton (H⁺) from the strong acid in the first step. This protonation forms an oxonium ion, which turns the alkoxy group (-OR) into a good leaving group (R-OH). The highly nucleophilic iodide ion (I⁻) can then attack the adjacent carbon atom, leading to the cleavage of the C-O bond.

7. What is an example of an electrophilic substitution reaction in an aromatic ether like anisole?

A classic example is the Friedel-Crafts alkylation of anisole. When anisole (methoxybenzene) is treated with an alkyl halide like methyl chloride (CH₃Cl) in the presence of a Lewis acid catalyst such as anhydrous AlCl₃, the activating methoxy group (-OCH₃) directs the incoming methyl group to the ortho and para positions. The major product formed is 4-methylanisole (p-methylanisole) due to less steric hindrance compared to the ortho product.

8. How does the formation of peroxides make the storage of ethers hazardous?

When exposed to air and light, ethers can undergo autoxidation, a free-radical reaction with oxygen to form unstable compounds called hydroperoxides. These peroxides are a significant safety hazard because they are highly explosive, especially when concentrated. If an old sample of ether containing peroxides is distilled, the less volatile peroxides can concentrate in the distillation flask and detonate violently upon heating. This is why ethers should be stored in dark, airtight containers and tested for peroxides before distillation.