1.3 Bonding

Question 1

The boiling point of iodomethane (CH3I) is higher than that of fluromethane (CH3F) even though the electronegativity of iodine is less than that of fluorine. Why?

Answer 1

• iodine is bigger than fluorine so the VDWs forces between CH3I molecules are stronger than those between CH3F molecules
• the dipole-dipole forces between CH3F molecules are stronger than those between CH3I molecules
• The VDWs forces are stronger than the dipole-dipole forces so these dominate