Question

Arrange the following in order of property indicated for each set.
\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO, C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{OH, C}}{{\text{H}}_{\text{3}}}{\text{OC}}{{\text{H}}_{\text{3}}}{\text{, C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}\](increasing order of boiling points)

Answer 1

Hint: We must have to remember that the boiling point is one of the physical properties of the compound. The boiling point is important for phase transfer property. The boiling point means liquid to gas transferring point. The temperature at first gaseous molecules exit from the liquid form of the compound. The boiling point of molecules is very important for the distillation process. The molecular formula of ethanol is \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{OH}}\]. The molecular formula of acetone is \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{OC}}{{\text{H}}_{\text{3}}}\]. The molecular formula of acetaldehyde is \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\]. The molecular formula of propane is \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}\].

Complete answer:
We have to remember that the boiling point of the molecule depends on the molecular mass, type of bonding in the molecule and functional group in the molecule.
If we want to order the boiling point of the molecules, first know the molecular mass of the given molecules, the type of bonding in the molecules and also depend on Van Der Waals force and dipole-dipole interaction.
The molecular mass of \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}\] is \[{\text{44g}}\].
The molecular mass of \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{OH}}\] is \[{\text{46g}}\].
The molecular mass of \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{OC}}{{\text{H}}_{\text{3}}}\] is \[{\text{46g}}\].
The molecular mass of \[{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}\] is \[{\text{44g}}\].
According to mass wise, acetone and ethanol have higher mass than acetaldehyde and propane. Ethanol having hydrogen bonds is the reason ethanol has the highest boiling point compared to other given molecules. Propane having weak Van Der Waals force than other molecules. Hence, propane has a lower boiling point than other given molecules.
Now, comparing acetone and acetaldehyde, acetaldehyde has more Dipole-Dipole interaction than acetone, hence, acetaldehyde having higher boiling point than acetone.
The increasing order of the boiling point of the given molecules is
\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}{\text{ < C}}{{\text{H}}_{\text{3}}}{\text{OC}}{{\text{H}}_{\text{3}}}{\text{ < C}}{{\text{H}}_{\text{3}}}{\text{CHO < C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{OH}}\]

Note:
We must have to remember that the molecule which having highest mass compare to the other molecules, that will having high boiling point compare to other. If two molecules having same molecular mass means, then next focus on the hydrogen bonding and Van Der Waals force. If two molecules having same molecular mass, one molecule is having hydrogen bond and other one not having hydrogen bond means, molecule which present hydrogen bond that is stronger than other one. Hence, the molecule has a hydrogen bond that is high boiling point. If two molecules have the same mass but both are not having hydrogen bonds, the next focus on the Van Der Waals force in the molecules. The molecule which has the lowest Vander Waals force has a lower boiling point than others. The Dipole-Dipole interaction is also important for boiling point.