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 factors influencing the boiling point of alkyl halides.
- Boiling point is determined by molecular weight, degree of branching, and intermolecular forces, particularly van der Waals forces.
- Generally, increased molecular mass and reduced branching lead to higher boiling points.

Step 2: Analyze the provided compounds:

• Option 1: CH₃CH₂Br — Ethyl bromide (Note: This is an alkyl bromide, not an alkyl chloride. Bromine's higher atomic mass compared to chlorine results in a higher boiling point).
• Option 2: C₆H₅CH₂Cl — Benzyl chloride (Characterized by a bulky structure and higher molar mass).
• Option 3: (CH₃)₂CHCl — Isopropyl chloride (Features a branched structure, leading to a moderate boiling point).
• Option 4: CH₃Cl — Methyl chloride (The smallest molecule with the lowest molar mass and minimal van der Waals interaction).

Step 3: Identify the compound with the lowest boiling point.
- Methyl chloride (CH₃Cl) possesses the lowest molecular weight and exhibits the least polarizability.
- Consequently, it experiences the weakest intermolecular forces, resulting in the lowest boiling point.

Final Answer: CH₃Cl (Option 4)