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Saw this question on a Kaplan FL test and I didn't agree with the explanation so I just past it off as them being wrong. I decided to look for the answer, found this thread http://forums.studentdoctor.net/showthread.php?t=443117 , but still have not changed my stance.
Basically, the question asks which of these molecules can hydrogen bond with glucose.
The relevant structure has amine groups that are bonded to aromatic carbons. The amine groups had their hydrogens replaced with methyl's , so instead of being NH2 they are N(CH3)2. Nitrogen still has a lone pair.
-They say that this structure (if you can visualize) cannot hydrogen bond because it does not have acidic hydrogens.
I thought they can still be hydrogen bond acceptors thru their lone pairs, and thus hydrogen bond. Is this not similar to how carbonyl oxygens can be hydrogen bond acceptors due to their extra e- density? If the question had said "hydrogen bond among by itself" it would make sense, but the way they have it now does not make sense to me.
Basically, the question asks which of these molecules can hydrogen bond with glucose.
The relevant structure has amine groups that are bonded to aromatic carbons. The amine groups had their hydrogens replaced with methyl's , so instead of being NH2 they are N(CH3)2. Nitrogen still has a lone pair.
-They say that this structure (if you can visualize) cannot hydrogen bond because it does not have acidic hydrogens.
I thought they can still be hydrogen bond acceptors thru their lone pairs, and thus hydrogen bond. Is this not similar to how carbonyl oxygens can be hydrogen bond acceptors due to their extra e- density? If the question had said "hydrogen bond among by itself" it would make sense, but the way they have it now does not make sense to me.
