Which of the following has the lowest boiling point?

Chloromethane

The boiling points of organic compounds are influenced by various factors, including intermolecular forces, molecular weight, and molecular structure. Generally, compounds with stronger intermolecular forces tend to have higher boiling points.

Comparing the given options, we can consider the intermolecular forces involved in each compound:

Option 1: Dichloromethane (CH₂Cl₂)

Dichloromethane has dipole-dipole interactions between its polar C-Cl bonds. These dipole-dipole interactions contribute to the intermolecular forces in the compound.

Option 2: Dibromomethane (CH₂Br₂)

Dibromomethane also has dipole-dipole interactions due to the polar C-Br bonds. However, bromine is larger and more polarizable than chlorine, resulting in stronger dipole-dipole interactions.

Option 3: Chloromethane (CH₃Cl)

Chloromethane has dipole-dipole interactions as well, but it has a smaller molecular size and less polarizable chlorine atom compared to bromine. Therefore, its dipole-dipole interactions are expected to be weaker than those in dibromomethane.

Option 4: Bromomethane (CH₃Br)

Bromomethane has dipole-dipole interactions resulting from the polar C-Br bond. Since bromine is larger and more polarizable than chlorine, the dipole-dipole interactions in bromomethane are stronger than those in chloromethane.

Based on these considerations, we can conclude that the compound with the lowest boiling point among the given options is Option 3: Chloromethane (CH₃Cl). It is expected to have weaker intermolecular forces compared to the other compounds due to the smaller size and lower polarizability of the chlorine atom.