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Question: Which of the following has the highest boiling point? A. \[{C_3}{H_7}Cl\] B. \[{C_4}{H_9}Cl\] ...

Which of the following has the highest boiling point?
A. C3H7Cl{C_3}{H_7}Cl
B. C4H9Cl{C_4}{H_9}Cl
C. CH3CH(CH3)CH2ClC{H_3}CH\left( {C{H_3}} \right)C{H_2}Cl
D. (CH3)3C−Cl{\left( {C{H_3}} \right)_3}C - Cl

Explanation

Solution

Boiling point of a substance is a physical property of the substance. It depends on the structure and shape of a molecule under consideration.

Complete answer:
Boiling point is the temperature at which the vapor pressure of a liquid substance becomes equal to the pressure above the liquid, thus the liquid goes to the vapor phase. The boiling point of water is 100∘C100^\circ C at sea level but on decreasing pressure the water boils at lower temperature. Thus boiling point depends on change in pressure.
Besides pressure, the boiling point of the substance depends on several other factors. The given molecules are organic compounds containing compounds of carbon, hydrogen and halogens. For these molecules boiling point is dependent on the structure and shape.
Boiling point is greatly affected by the forces present between molecules which in the case of alkyl halides are Van Der Waals interactions. Boiling points increase with the increase in the number of carbon atoms. As the number of carbon atoms increases in a straight chain the surface area increases and the boiling point increases.
However if branching occurs rather than increasing in a straight chain the surface area decreases as the molecule becomes like a sphere. Hence the intermolecular Van Der Waals force of interaction decreases and therefore decreases boiling point.
Of the given molecules C4H9Cl{C_4}{H_9}Cl is the longest chain alkyl halide. So it has the highest boiling point. The molecule C3H7Cl{C_3}{H_7}Cl is lower in chain length and CH3CH(CH3)CH2ClC{H_3}CH\left( {C{H_3}} \right)C{H_2}Cl and (CH3)3C−Cl{\left( {C{H_3}} \right)_3}C - Cl are branched chain molecules so they posses lower boiling points.

Note:
The boiling point of organic compounds is a unique feature of the compounds. It gives valuable information about the physical and structural properties. It helps in the recognition as well as characterization of a compound.