Question

Which of the following alkyl chloride will have the lowest boiling point?

• A. CH$_3$CH$_2$Br
• B. C$_6$H$_5$CH$_2$Cl
• C. (CH$_3$)$_2$CHCl
• D. CH$_3$Cl

Hint:

To determine the lowest boiling point, consider the size of the molecule and the types of intermolecular forces present. Small molecules like CH$_3$Cl have lower boiling points than larger, more complex molecules.

Answer 1

The Correct Option is D

Step 1: Understand what affects boiling point of alkyl halides.
- Boiling point depends on the molecular weight, branching, and intermolecular forces (especially van der Waals forces).
- Generally, higher molecular mass and less branching result in higher boiling points.

Step 2: Analyze the given compounds:

• Option 1: CH₃CH₂Br — Ethyl bromide (Not an alkyl chloride; bromine is heavier than chlorine and gives higher boiling point).
• Option 2: C₆H₅CH₂Cl — Benzyl chloride (bulky structure, higher molar mass).
• Option 3: (CH₃)₂CHCl — Isopropyl chloride (branched structure, moderate boiling point).
• Option 4: CH₃Cl — Methyl chloride (smallest, lowest molar mass, least van der Waals interaction).

Step 3: Identify the compound with lowest boiling point.
- Methyl chloride (CH₃Cl) has the lowest molecular weight and is the least polarizable.
- It exhibits the weakest intermolecular forces, hence has the lowest boiling point.

Final Answer: CH₃Cl (Option 4)