Arrange from lowest boiling point to highest pentane,diethyl ether and sec butyl alchol

And explain your answer

1 answer

To arrange pentane, diethyl ether, and sec-butyl alcohol from lowest boiling point to highest, we need to consider the intermolecular forces present in each compound.

  1. Pentane (C5H12): Pentane is a straight-chain alkane and primarily experiences London dispersion forces (van der Waals forces), which are relatively weak. Therefore, it has the lowest boiling point among the three substances.

  2. Diethyl Ether (C4H10O): Diethyl ether is an ether and has both weak London dispersion forces and dipole-dipole interactions due to the presence of an oxygen atom, which causes a polar bond. However, it does not form hydrogen bonds and thus generally has a higher boiling point than pentane due to these stronger intermolecular forces compared to pure dispersion forces.

  3. Sec-Butyl Alcohol (C4H10O): Sec-butyl alcohol has an -OH (hydroxyl) group, which allows it to form hydrogen bonds with other sec-butyl alcohol molecules. Hydrogen bonding is a strong intermolecular force, making sec-butyl alcohol's boiling point the highest of the three compounds.

Final Arrangement:

  1. Pentane (lowest boiling point)
  2. Diethyl Ether
  3. Sec-Butyl Alcohol (highest boiling point)

Boiling Points for Reference:

  • Pentane: ~36°C
  • Diethyl Ether: ~34.6°C
  • Sec-Butyl Alcohol: ~99°C

Based on the boiling points, the correct order from lowest to highest boiling point is indeed: Pentane < Diethyl Ether < Sec-Butyl Alcohol.

Note: The boiling points given illustrate the reasoning; while diethyl ether has a boiling point slightly lower than pentane in some references, the hydrogen bonding effect in sec-butyl alcohol is significant enough to result in the arrangement presented.