Intermolecular Forces and Solubility

Intermolecular Forces

A. Intermolecular Forces in Butanone and n-butane

(i) Butanone (CH3COCH2CH3)

• Structure: The structure of butanone is provided, showing a central carbonyl group (C=O) which introduces polarity.
• Polarity: Butanone is polar due to the presence of the carbonyl group and its asymmetrical structure.
• Intermolecular Forces:
  • London Dispersion Forces: Present in all molecules.
  • Dipole-Dipole Interactions: Present because butanone is a polar molecule.
  • Hydrogen Bonding: Not present, as the oxygen atom is not bonded directly to a hydrogen atom.

(ii) n-butane (CH3CH2CH2CH3)

• Structure: The structure of n-butane is provided, showing a symmetrical arrangement of carbon and hydrogen atoms.
• Polarity: n-butane is nonpolar due to its symmetrical structure.
• Intermolecular Forces:
  • London Dispersion Forces: The only significant intermolecular force present.

B. Solubility in H2O

• Solubility Difference: Butanone is much more soluble in H2O than n-butane.
• Explanation:
  • Polarity: Butanone is polar and can form hydrogen bonds with water molecules via the lone pair of electrons on the oxygen atom.
  • n-butane: n-butane is nonpolar and cannot form hydrogen bonds with water, thus its solubility is lower.