Test 2: Number of Hydrogen Bonding Sites Question

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Tiffany Chao 2H
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Joined: Fri Aug 09, 2019 12:17 am

Test 2: Number of Hydrogen Bonding Sites Question

Postby Tiffany Chao 2H » Fri Nov 29, 2019 3:48 pm

I've been hearing mixed answers. What's the correct number of H-bonding sites and what's the explanation? Thanks

Lauren Haight 1E
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Re: Test 2: Number of Hydrogen Bonding Sites Question

Postby Lauren Haight 1E » Fri Nov 29, 2019 3:53 pm

On my test, there was a caffeine molecule and students needed to identify hydrogen bonding sites. There were 6, 4 due to lone pairs 4 N atoms and 2 due to lone pairs on 2 O molecules. I have been hearing that DNA was used as an example for other tests, so you may want to double check with someone if your test had this question, and not the question with caffeine.

ishaa Diwakar 4E
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Joined: Wed Sep 11, 2019 12:17 am

Re: Test 2: Number of Hydrogen Bonding Sites Question

Postby ishaa Diwakar 4E » Fri Nov 29, 2019 4:05 pm

I don't remember the exact number, but this question confused me too. It's supposed to be the total number of potential H-bonding sites on the molecule, and this can be for H-bond sites with ANY molecule, not only more of the same molecule. So, it will be the number of Hydrogens bonded to N,O, and F, as well as the number of partially charged N,O and F with lone pairs.

Jessica Chen 2C
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Joined: Thu Jul 11, 2019 12:17 am

Re: Test 2: Number of Hydrogen Bonding Sites Question

Postby Jessica Chen 2C » Sun Dec 01, 2019 9:20 pm

I'm a bit confused by the mixed answers too, I put 8 and got it right on my test. There were 4 N with 1 lone pair each, so that's 4 hydrogen bonding sites; there were 2 O with 2 lone pairs each, so that's another 4 hydrogen bonding sites, giving me 8 in total. In theory, if there were any H attached to N, O, or F, that would be a hydrogen bonding site too, but all the H in the caffeine molecule were bonded to C.


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