Question

The boiling points of alkyl halide are higher than those of corresponding alkanes because of:
A. Dipole-dipole interaction
B. Dipole induced dipole interaction
C. H-bonding
D. None of the above

Answer 1

Hint Alkanes are non polar in nature. They have weak van der waals forces of attraction. The size of the melting or boiling point depends on the strength of the intermolecular forces. In alkyl halide $C - X$ bond formed is polar in nature and has strong intermolecular attraction as compared to their corresponding compound.

Complete answer:
Alkyl halides (also known as haloalkanes) are compounds in which one or more hydrogen atoms in an alkane have been replaced by halogen atoms. All atoms and molecules have a weak attraction for one another, known as van der Waals attraction. In alkyl halides, $C - X$ bond is polar. The carbon-halogen bonds are polar, because the electron pair is pulled closer to the halogen atom than the carbon. This is due to the halogens being more electronegative than carbon atoms. As bonds become more polarized, the charges on the atoms become greater, which leads to greater intermolecular attractions, which leads to higher boiling points. In an alkyl halide and alkane of comparable size and shape, the alkyl halide has the higher boiling point the difference is due almost entirely to the greater polarizability of the three unshared pairs of electrons on halogen compared with the polarizability of shared electron pairs of the hydrocarbon.
Therefore the dipole dipole interactions have an important role in having higher boiling point in alkyl halide compounds.

**Therefore the correct option is option A.

Note:**
Boiling Point depends upon the intermolecular forces of attraction and hence the boiling points of chlorides, bromides and iodides are considerably higher than those of the hydrocarbons of comparable molecular mass. As we go down in a homologous series of haloalkanes, the forces of attraction become stronger due to increase in molecular size and its mass, hence the boiling point increases down the homologous series.