Tag: physical properties of ethers

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Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

Ethers have lower boiling points than their corresponding isomeric alcohols because of?

  1. hydrogen bonding in alcohols that is absent in ethers due to low polarity

  2. hydrogen bonding in ethers due to high polarity

  3. insolubility of ethers in water due to less polarity

  4. inertness of ethers as compared to alcohols.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ethers ROR cannot form intermolecular Hydrogen bond due to the absence of H attached with the electronegative atom as N/O/F, but in case of alcohols, they have -OH which can undergo intermolecular hydrogen bonding and that increases their boiling point.

Thus, Ethers have lower boiling points than their corresponding isomeric alcohols because of hydrogen bonding in alcohols that is absent in ethers due to low polarity.

Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

Correct order of boiling points among following is: $\underset{(X)}{CH _3(CH _2) _3CH _3}, \,\,\,\,\underset{(Y)}{C _2H _5OC _2H _5},\,\,\,\,\,\,\underset{(Z)}{CH _3(CH _2) _3OH}$

  1. X > Y > Z

  2. Y > X > Z

  3. Z > X > Y

  4. Z > Y > X
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The boiling point of a molecule depends on the strength of intermolecular interaction such as Vandewaal's attraction, hydrogen bonding etc.

Alkanes, such as $\underset{X}{CH _3(CH _2) _3CH _3}$, being non-polar have the weakest force of attraction called dispersion or London forces.
Ethers, such as $\underset{(Y)}{C _{2}H _{5}OC _2H _5}$, have small dipole moment or weakly polar thus have dipole-dipole interaction. This is stronger than the London forces.
Alcohols, such as $\underset{(Z)}{CH _3(CH _2) _3OH}$, are polar molecules, therefore, have strong dipolar interaction. Moreover, they form an intermolecular hydrogen bond that further increases the attraction (association).

Hence the order of their boiling point will be:
$\underset{(Z)}{CH _3(CH _2) _3OH}>\underset{(Y)}{C _{2}H _{5}OC _2H _5}>\underset{X}{CH _3(CH _2) _3CH _3}$

OR $Z>Y>X$

Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

The compound which has highest boiling point among the following is: 

  1. diethyl ether

  2. ethanol

  3. methanol

  4. water
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Boiling point of Diethyl ether $=34.6^0C$


Boiling point of Ethanol $=78.5^0C$

Boiling point of Methanol $=64.7^0C$

Boiling point of Water $=100^0C$

Hydrogen bonding in water and alcohol due to which they have higher boiling points.

Here, water has the highest boiling point among others.

 So correct answer is option D.

Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

The high boiling point of ethanol $(78.2^o C)$ compared to dimethyl ether $(-23.6^o C)$, though both having the same molecular formula $\displaystyle { C } _{ 2 }{ H } _{ 6 }O$, is due to:

  1. hydrogen bonding

  2. ionic bonding

  3. co-ordinate covalent bonding

  4. resonance
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The high boiling point of ethanol $(78.2 ^oC)$ compared to dimethyl ether $(-23.6^oC)$, though both having the same molecular formula $C _2H _6O$, is due to Hydrogen bonding.
Hydrogen bonding is observed when H atom is attached to more electronegative N, F or O atom.
Ethanol molecules are associated due to hydrogen bonding. This results in higher boiling point.
However, hydrogen bonding is not possible in dimethyl ether.

Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

Maximum boiling point would be shown by:

  1. $\displaystyle { CH } _{ 3 }-O-{ CH } _{ 3 }$
  2. $\displaystyle { C } _{ 2 }{ H } _{ 5 }-O-{ C } _{ 2 }{ H } _{ 5 }$
  3. $\displaystyle { CH } _{ 3 }-{ CH } _{ 2 }-{ CH } _{ 2 }-OH$
  4. $\displaystyle ({ CH } _{ 3 }{ ) } _{ 2 }CH-OH$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Maximum boiling point would be shown by n propanol, $\displaystyle { CH } _{ 3 }-{ CH } _{ 2 }-{ CH } _{ 2 }-OH$.
In n-propanol, the molecules are associated due to hydrogen bonding. Hence, the boiling point is higher.
In dimethyl ether and diethyl ether, the boiling point is lower as hydrogen bonding is not possible.
The extent of the hydrogen bonding in isopropanol is lower than that in n-propanol due to +I effect of two methyl groups.
Also, as the degree of branching increases, the boiling point decreases.

Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

Among ethanol, dimethyl ether, methanol and propanal, the isomers are

  1. ethanol, dimethyl ether, methanol and propanal

  2. ethanol and methanol

  3. ethanol, dimethyl ether, and methanol

  4. ethanol and dimethyl ether
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ethanol $(C _2H _5OH)$ and dimethyl ether $(CH _3-O-CH _3)$ have same molecular formula but different functional groups, so they are isomers.