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hydrogen bonding

Posted: Tue Nov 13, 2018 2:51 pm
by alanaarchbold
How does hydrogen bonding explain higher melting points?

Re: hydrogen bonding

Posted: Tue Nov 13, 2018 2:54 pm
by ChathuriGunasekera1D
Hi! Hydrogen bonding is stronger than most intermolecular forces, so it is requires more energy to break those IMFs, and therefore needs a higher temperature for the compound to move from solid to liquid.

Re: hydrogen bonding

Posted: Tue Nov 13, 2018 8:36 pm
by Alexa_Henrie_1I
^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs.

Re: hydrogen bonding

Posted: Tue Nov 13, 2018 8:44 pm
by Nicolette_Canlian_2L
Alexa_Henrie_3B wrote:^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs.

So does this mean GC base pairs have stronger bonds than AT base pairs?

Re: hydrogen bonding

Posted: Tue Nov 13, 2018 10:35 pm
by Kassidy Tran 1E
Nicolette_Canlian_3G wrote:
Alexa_Henrie_3B wrote:^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs.

So does this mean GC base pairs have stronger bonds than AT base pairs?

Yes, because G-C base pairs have three hydrogen bonds rather than two, like in A-T base pairs. Since there are more hydrogen bonds, it has a higher melting point.

Re: hydrogen bonding

Posted: Thu Nov 15, 2018 2:20 pm
by Hannah Pham 1D
Hydrogen bonding takes more energy to break because it is stronger than most intermolecular forces.

Re: hydrogen bonding

Posted: Thu Nov 15, 2018 2:50 pm
by Aurbal Popal
Chathuri Gunasekera 1G wrote:Hi! Hydrogen bonding is stronger than most intermolecular forces, so it is requires more energy to break those IMFs, and therefore needs a higher temperature for the compound to move from solid to liquid.


I thought covalent bonds and ionic bonds were stronger? Or do those not count as IMF?

Re: hydrogen bonding

Posted: Thu Nov 15, 2018 6:20 pm
by Nicolette_Canlian_2L
Kassidy Tran 1F wrote:
Nicolette_Canlian_3G wrote:
Alexa_Henrie_3B wrote:^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs.

So does this mean GC base pairs have stronger bonds than AT base pairs?

Yes, because G-C base pairs have three hydrogen bonds rather than two, like in A-T base pairs. Since there are more hydrogen bonds, it has a higher melting point.

ahhh I see. Thank you!

Re: hydrogen bonding

Posted: Sun Nov 18, 2018 11:12 pm
by Ahmed Mahmood 4D
Hydrogen bonding is extremely strong. Because of this, it takes more heat to break hydrogen bonds, leading to higher melting points among hydrogen bonds.

Re: hydrogen bonding

Posted: Sun Nov 18, 2018 11:51 pm
by Pritish Patil 1K
Hydrogen bonding is stronger than most other IMF so it takes more energy to break.

Re: hydrogen bonding

Posted: Mon Nov 19, 2018 12:23 am
by 505211599
Hydrogen bonding is the strongest IMF so the energy needed to separate these molecules is higher. Therefore the melting point would be higher.

Re: hydrogen bonding

Posted: Tue Nov 20, 2018 8:06 am
by ChathuriGunasekera1D
Aurbal Popal wrote:
Chathuri Gunasekera 1G wrote:Hi! Hydrogen bonding is stronger than most intermolecular forces, so it is requires more energy to break those IMFs, and therefore needs a higher temperature for the compound to move from solid to liquid.


I thought covalent bonds and ionic bonds were stronger? Or do those not count as IMF?


Covalent bonds and ionic bonds are between the atoms within the molecules (called INTRAmolecular forces). The bond between the C and H is covalent in methane (intramolecular force), but the bond between H and H that connect whole methane molecules to each other is a dispersion force (intermolecular force).

It gets a little bit confusing because ionic bonding can occur between Na and Cl within an individual salt molecule, but it also occurs between the Na of one molecule and the Cl of another molecule. So technically, ionic bonding is both an intramolecular force and an intermolecular force. The same cannot be said about covalent bonds.

Going back to boiling point; when you heat a substance, you are breaking apart one molecule from another, not the individual atoms in one molecule. For example in methane, you are separating one CH4 from another, not one CH4 into one C and 4 Hs. Covalent and ionic bonding (the intra type) is not considered when determining boiling point. Hope I answered the question!