6.3.7 - Physical Properties of Alcohols

• boiling points

  higher than alkanes with the same number of carbons because alkanes only have London forces but alcohols also have dipole-dipole interactions and hydrogen bonds due to -OH so more energy to overcome them

  higher boiling point as carbon chain increases because number of electrons increases so more London forces
• solubility in water

  small alcohols are completely soluble

  hydrogen bonds are broken between pure water molecules and pure alcohol molecules and new hydrogen bonds form between water and alcohol molecules

  energy to break bond is compensated by energy to make it
• trend in solubility as carbon chain increases

  solubility decreases as carbon chain increases as alkyl 'tail' can't form hydrogen bonds with water so fewer hydrogen bonds form so energy doesn't compensate for energy to break hydrogen bonds in the first place