Edward A. Berry wrote:
> Dear all,
> Is it possible for a Cl atom attached to an aromatic ring to
> accept an H-bond from His NE2?
> I'm modeling a low-resolution ligand structure and my favorite fit
> shows such a bond, but it is possible the ring is flipped and
> an OH or -C=O on the other side of the ring actually make the H-bond.
>
> Thanks,
> Ed
>
A number of people expressed the view that this kind of interaction is possible.
Narayanan Ramasubbu provided a reference:
Ramasubbu, N., Parthasarathy, R. and Murray-Rust, P. Angular preferences of intermolecular forces around halogen centers,
Preferred directions of approach of electrophiles and nucleophiles around carbon-halogen bond. J. Am. Chem. Soc., 108, 4308-4314, 1986.
The interaction described is not actually an H-bond, but a direct HOMO-LUMO orbital
interaction between the halogen and nucleophile, however the distance is significantly
less than sum of vdw radii, for example about 3.0 A, making it look
like an H-bond. Thus it wouldn't require NE2 nitrogen to be protonated.
Don't know how much this would contribute to binding energy, as compared
to a hydrogen bond.
Thanks, and
Productive new year to all,
Ed
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