Dear Dmitry Nilov,
> Amines of the type NHRR' are chiral because of the lone pair of electrons.
> The energy barrier for inversion of stereocenter is about 7 klcal/mol.
> I wonder if there is some mechanism in GAFF to prevent the amine
> inversion. I suppose that 7 klcal/mol barrier crossing is a low-probability
> event on the time scale of MD simulations, nevertheless I've observed
> inversion of my amine during equilibration stage.
I am not sure you are right when you say that a tertiary amine NHRR'
is chiral. I think the nitrogen of such a tertiary amine NHRR' is NOT
asymmetric. I even wonder if this interconversion is not normal: The
only question is how OFTEN during MD simulations this should be
observed. On the contrary, quaternary ammoniums (+)NHRR'R" do have an
asymmetric nitrogen & present an optical activity.
Just my personal opinion...
Please, see
http://en.wikipedia.org/wiki/Amine#Chirality (which is ambiguous)
& better
http://en.wikibooks.org/wiki/Organic_Chemistry/Amines#Chirality
& then
http://home.clara.net/rod.beavon/chiralit.htm
regards, Francois
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Received on Wed Apr 14 2010 - 13:00:03 PDT
