which one has higher boiling point?

[sakthivs]

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Ok I just want to clarify which one has the higher boiling point? H2O or HOCH2CH2OH? would it be H2O because HOCH2CH2OH is nonpolar? Or would it be HOCH2CH2OH because its bigger than H2O? I am just a little confused atm. Thanks in advance.

 

[ChrisM07]

When I look at this, I see that the second molecule has two OH groups while H20 only has one. In my mind, I think, "double the hydrogen bonding power". This is why the second group wins in terms of H bonding ability and subsequently the higher BP.

Side Note: This compound's name is ethylene glycol, and a quick search shows that it has a BP of 193 C while regular water boils, as we know, at 100 C. Ethylene glycol is used specifically in windshield fluid for our cars and is able to disrupt the H bonds of water, therefore lowering the freezing point of water (to around -40 C).

 

[calvzzz]

When I look at this, I see that the second molecule has two OH groups while H20 only has one. In my mind, I think, "double the hydrogen bonding power". This is why the second group wins in terms of H bonding ability and subsequently the higher BP.

I concur.

 

[sakthivs]

cool ty makes sense.

 

[Psa]

Ok I just want to clarify which one has the higher boiling point? H2O or HOCH2CH2OH? would it be H2O because HOCH2CH2OH is nonpolar? Or would it be HOCH2CH2OH because its bigger than H2O? I am just a little confused atm. Thanks in advance.

Just an FYI: HOCH2CH2OH is polar, not nonpolar! Remember, OH's indicate that the molecule is polar.

 

[sakthivs]

so whenever you have OH's in the molecule it will always be polar?

 

[sskater]

so whenever you have OH's in the molecule it will always be polar?

You know looking at this.

IF we had trans-C2H2OH2, I don't think it will be polar due to the dipoles canceling.
But with ethylene glycol, the carbon structure is flexible enough that two -OH's are able to form a internal hydrogen bond that makes the 3D structure of the molecule bent in a way that makes it so the dipoles still point in the same general direction.
But any molecule with O-H bonds can do hydrogen bonding and that is the highest IMF.

 

[FeralisExtremum]

When I look at this, I see that the second molecule has two OH groups while H20 only has one. In my mind, I think, "double the hydrogen bonding power". This is why the second group wins in terms of H bonding ability and subsequently the higher BP.

But doesn't water have two H's available for hydrogen bonding, making the 'hydrogen bonding power' exactly the same? How would this explanation work if you were comparing (for example) hydrogen peroxide to ethylene glycol?

 

[Psa]

But doesn't water have two H's available for hydrogen bonding, making the 'hydrogen bonding power' exactly the same? How would this explanation work if you were comparing (for example) hydrogen peroxide to ethylene glycol?

You have to take into account all of the intermolecular forces. Since ethylene glycol will also have London dispersion force due to CH2CH2, it will have a higher BP than hydrogen peroxide.

 

[FeralisExtremum]

You have to take into account all of the intermolecular forces. Since ethylene glycol will also have London dispersion force due to CH2CH2, it will have a higher BP than hydrogen peroxide.

That makes sense. So I guess the right answer to the OP's question is that ethylene glycol and water both have "double hydrogen bond" power, but ethylene glycol has the added advantage of the London dispersion forces due to increased mass.