alcohol boiling point

[joonkimdds]

I just read from Kaplan BB that alcohol has significantly higher boiling point than those of the analogous hydrocarbon due to H bonding.

but isn't alcohol supposed to have low boiling point?
we always use alcohol in our lab to burn something 😛

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[Decan]

Nope...kaplan is correct.

 

[Archie376]

Alcohol has H-bonding. Molecules stick together and are less volatile. It takes more heat to break them apart and achieving boiling.

 

[joonkimdds]

Alcohol has H-bonding. Molecules stick together and are less volatile. It takes more heat to break them apart and achieving boiling.

but isn't H-bonding ionic bonding and so it's easy to break compared to covalent bonding and requires less heat to break them apart?

 

[DrDDSman]

but isn't H-bonding ionic bonding and so it's easy to break compared to covalent bonding and requires less heat to break them apart?

From what I recall, A hydrogen bond isn't a real "bond" its an intermolecular attraction (eg, dipole-dipole).

I'm pretty sure you have your concepts a little mixed up, refer back to your college text or the kaplan book for a simplified explanation.

 

[georgiadat]

The longer the hydrocarbon chain, the higher the boiling point. Methane is lower bp than hexane. If you assume that hydrogen bonding is actual bonding (like ionic or covalent) then you will have a very large group of molecules "stuck" together that must be separated in order to achieve boiling. Alcohols are polar and thus have hydrogen bonding... hydrocarbons are not polar therefore no hydrogen bonding. Since hydrogen bonds are VERY weak, you can boil alcohol at a fairly low temperature in contrast, if alcohol molecules were held together with the strength of a covalent or ionic bond, it would take an incredible amount of heat to reach their bp. Sorry for the long response, but I am incredibly bored today.

 

[joonkimdds]

The longer the hydrocarbon chain, the higher the boiling point. Methane is lower bp than hexane. If you assume that hydrogen bonding is actual bonding (like ionic or covalent) then you will have a very large group of molecules "stuck" together that must be separated in order to achieve boiling. Alcohols are polar and thus have hydrogen bonding... hydrocarbons are not polar therefore no hydrogen bonding. Since hydrogen bonds are VERY weak, you can boil alcohol at a fairly low temperature in contrast, if alcohol molecules were held together with the strength of a covalent or ionic bond, it would take an incredible amount of heat to reach their bp. Sorry for the long response, but I am incredibly bored today.

if you are incredibly bored today, just come over to my house and teach me DAT

 

[doc toothache]

I just read from Kaplan BB that alcohol has significantly higher boiling point than those of the analogous hydrocarbon due to H bonding.

but isn't alcohol supposed to have low boiling point?
we always use alcohol in our lab to burn something 😛

They were comparing methane to methanol, ethane to ethanol, propane to propanol, etc. Get it?

 

[HeatingHomer]

I just read from Kaplan BB that alcohol has significantly higher boiling point than those of the analogous hydrocarbon due to H bonding.

but isn't alcohol supposed to have low boiling point?
we always use alcohol in our lab to burn something 😛

Alcohol has a low boiling point when compared to water. However, when compared to other organic compounds it would be considered high.