Question
Explain boiling point of alkyl halides.
✓
Answer
→ Molecules of organic halogen compounds are generally polar.
→ Due to greater polarity as well as higher molecular mass as compared to the parent hydrocarbon, the intermolecular forces ofattraction (dipole-dipole and van der Waals) are
stronger in the halogen derivatives.
→ That is why the boiling points of chlorides, bromides and iodides are considerably higher than those of the hydrocarbons of comparable molecular mass.
→ The pattern of variation of boiling points of different halides is depicted in Fig.
→ For the same alkyl group, the boiling points of alkyl halides decrease in the order: RI> RBr> RCI> RF.
→ This is because with the increase in size and mass of halogen atom, the magnitude of van der Waal forces increases.
→ The boiling points of isomeric haloalkanes decrease with increase in branching (1°>2°>3°).
→ For example, 2-bromo-2- methylpropane has the lowest boiling point among the three isomers.
→ Due to greater polarity as well as higher molecular mass as compared to the parent hydrocarbon, the intermolecular forces ofattraction (dipole-dipole and van der Waals) are
stronger in the halogen derivatives.
→ That is why the boiling points of chlorides, bromides and iodides are considerably higher than those of the hydrocarbons of comparable molecular mass.
→ The pattern of variation of boiling points of different halides is depicted in Fig.
→ For the same alkyl group, the boiling points of alkyl halides decrease in the order: RI> RBr> RCI> RF.
→ This is because with the increase in size and mass of halogen atom, the magnitude of van der Waal forces increases.
→ The boiling points of isomeric haloalkanes decrease with increase in branching (1°>2°>3°).
→ For example, 2-bromo-2- methylpropane has the lowest boiling point among the three isomers.
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