Acetone- Water & Acetone-Ethanol & more examples of non-ideal solutions

Acetone- water & acetone-Ethanol are example of different strength of H-bonding by acetone.

Remember (1) Both water & alcohol are amphiporotic solvent , but Water is more acidic than ethanol.

(2) Acetone has a Basic doubly-bonded Oxygen,

(3) Acetone cannot form H-bond among themselves but greater dipole moment (Acetone’s dipole moment is 2.91D) & Basic oxygens of Acetone help it to form strong H-bond with either of two acidic protons of water. Thereby attractive forces gets strong.(consider hydrate formation & tautomerism to some extent as well, however they are not deciding factor here)

In fact, H-bonding of Acetone with water is more stronger than that of alcohol-water (acetone is completely miscible with water as well).

this is the reason, Alcohol- water has positive deviation but acetone-water has negative deviation

(4) the question remains why acetone -ethanol has positive deviation. If you consider its high dipole moment, its soluble in almost all organic solvents as well as water.

However, Its H-bonding with ethanol is not as strong as with water, due to greater hydrophobic part in ethanol as well as less acidic proton in ethanol./

Hence, Ethanol-water has positive deviation.

Also remember—

  • Octane + heptane,
  • ethanol + 1-butanol and
  • methyl acetate + methyl acrylate are near ideal solutions.
  • Methanol + acetone,
  • ethanol + acetone,
  • methanol + methyl acetate,
  • methanol + methyl acrylate,
  • isoamyl alcohol + isoamyl acetate,
  • octane + 1-butanol,
  • octane + 2-butanol,
  • octane + ethanol,
  • ethylene glycol and CCl4 and
  • octane + isopropanol mixtures deviate positively from an ideal solution.
  • Acetic acid and n-propanol,
  • cyclohexylamine + cyclohexanol,
  • phenol + acetophenone,
  • phenol + cyclohexanol, and
  • phenol + cyclohexanone, all deviate negatively from ideality.




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