Consider the following four halomethanes: , , , and . Although their permanent dipole moments strictly decrease in the order , what is the mathematically correct increasing order of their normal boili

Question

Consider the following four halomethanes: $CH_3Cl$, $CH_2Cl_2$, $CHCl_3$, and $CCl_4$. Although their permanent dipole moments strictly decrease in the order $CH_3Cl > CH_2Cl_2 > CHCl_3 > CCl_4$, what is the mathematically correct increasing order of their normal boiling points?

Prashant Kotian · Accepted Answer

Correct answer: A. Boiling points are dictated by the cumulative strength of all intermolecular forces. While dipole-dipole attractions decrease as the dipole moment drops from to , the molecular mass and the total number of polarizable electrons significantly increase with the addition of each heavy chlorine atom. This massive increase in London dispersion forces completely overrides the loss of dipole-dipole interactions, resulting in a strict monotonic increase in boiling point: .

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