Thanks to all who answer my question.My question was:
+a benzyl group
+a phenyl ring
I would like to know if that NH is a possible hydrogen bond
acceptor. I have not found two much information. Could anybody tell
me
any reference about that class of secondary amines and their role
as
hydrogen bond acceptors?
Thanks in advance
The answers Ihave got:
- Dick Caldwell wrote:
A weak one. You need to find a list of pKa's of amines - the usual
advanced organic texts will be a good start. I guess that yours will have
a pKa of about 7, cf. good amine bases (i.e. good H bond acceptors) at
about 11-12.
good luck, Dick Caldwell
- Jeremy Greenwood wrote
Hi Jose,>
>
> I am working with a molecule that contains a secondary amine
> group. Its sustituents are:
>
>
> +a benzyl group
> +a phenyl ring
>
i.e. :N(H)(CH2Ph)(Ph) <<-->> (H)N+(H)(CH2Ph)(Ph)> I would like to know if that NH is a possible hydrogen bond
> acceptor. I have not found two much information. Could anybody tell me
> any reference about that class of secondary amines and their role as
> hydrogen bond acceptors?(assuming you're interested in hydrogen bond acceptors in the
context of biological activity)If it's protonated, it's potentially a double hydrogen bond donor
If it's neutral, it's potentially a single hydrogen bond donor
and single hydrogen bond acceptor.The pKa is around 10, so it's most likely a potential double
hydrogen bond donor at physiogical pH. Whether or not it is protonated
in a given receptor will depend on the local environment.
The local environment will also determine how many hydrogen bonds
it participates in, since it's somewhat sterically crowded.
If it's not protonated, then the receptor environment (and/or
the rest of the molecule) will determine the chirality of the
nitrogen, so you can't say anything a priori about which direction
it can donates and accepts in.Hope this helps a little,
Jeremy
----------------------------------------------------------------------
Jeremy Greenwood jeremy $#at#$ greenwood.net
Department of Medicinal Chemistry bh +45 35306117
Royal Danish School of Pharmacy fx +45 35306040
Universitetsparken 2, DK-2100 Copenhagen, Denmark ah +45 32598030
----------------------------------------------------------------------
Hi Jose
- Richard L. wood wrote:
I'm not an expert on this topic.
That said, as I recall from my undergraduate sophomore inorganic chemistry,
the basicity of amines decreases as you go from
primary to secondary to tertiary, as the electron withdrawing power of the
R groups pulls the lone pair electrons closer to the nitrogen,
making it more difficult to donate those electrons to an acid. I would
think it would make it more difficult to act as an H-bond acceptor
as well. So I would think that H-bond acceptor strength would go ammonia >
primary amine > secondary amine.I hope this helps.
Richard
I don't think the benzyl group would make that much difference. (Unlike the
- Dave Shobe wrote:
phenyl group which is known to interact strongly with the nitrogen lone
pair).Accordingly, if you can't find a study on N-benzylaniline, a study of
N-methylaniline or N-ethylaniline would probably be close enough.Hopefully you are in a place with good literature searching tools. :-)
--David Shobe
Süd-Chemie Inc.
phone (502) 634-7409
fax (502) 634-7724
email dshobe $#at#$ sud-chemieinc.com
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