Cyclopropane exists in a form of ring. The angle between the carbon-carbon bonds is about 60 degrees which weaken the bond and increases its reactivity.
Since the bond weakens due to low bond angles, then why is its boiling point higher than propane?

Question

Cyclopropane exists in a form of  ring. The angle between the carbon-carbon bonds is about 60 degrees which weaken the bond and increases its reactivity.
Since the bond weakens due to low bond angles, then why is its boiling point higher than propane?

mayankdevnani · Answer

More POLARIZING POWER,more BOILING POINT

mayankdevnani · Answer

We can also say that :-
MORE THE INTERMOLECULAR FORCE,MORE THE BOILING POINT

mayankdevnani · Answer

As we know that there are LONDON DISPERSION FORCES,for cyclopropane, it causes RING STRAIN,
therefore,causing in MORE VOLUME.
More Volume means we need more energy
More energy means MORE BOILING POINT.

mayankdevnani · Answer

hope it helps :)

faiqraees · Answer

@mayankdevnani Cyclopropane has hydrogen-carbon bonds which are only very slightly polar and carbon-carbon bond which are non-polar. Even if you take into account the polarity of CH bonds, propane should have more boiling points since it have more CH bonds.

Intermolecular forces though are stronger in cyclopropane, the very low bond angle dominates its effect as seen from its reactivity. Electron-electron repulsions are very high due to 60 angle and the bonds become very weak.

Cyclopropane has very similar mass to propane and greater density than propane occupying effectively less volume than propane in its liquid phase.

faiqraees · Answer

Please tell me if I am wrong anywhere.

mayankdevnani · Answer

i think cyclopropane has greater volume

mayankdevnani · Answer

due to ring strain

faiqraees · Answer

No, they have lesser volume

anonymous · Answer

@Kainui

aaronq · Answer

You're talking about two different types of bonding; the deviation from the ideal bond angle weakens the INTRAmolecular bond, (i.e. the C-C bond) increasing it's susceptibility to breakage. But physical properties, like boiling point, are dictated by interactions between separate molecules (termed INTERmolecular forces) which for unsubstituted  hydrocarbons increase with the number atoms present. This is because - as mentioned earlier - there are more electrons/bonds to be polarized which sum up to a transient dipole moment of greater magnitude.

faiqraees · Answer

@aaronq So you're saying if a compound is reactive its because its intramolecular bonds are weak and if a compound has a low boiling point its because its intermolecular bonds are weak?

aaronq · Answer

yes