Dear Ling,
Your answer about tetragonal carbons goes in the same direction as my
initial feeling did,
but my feeling was only a feeling, just like yours.
I was wondering whether someone had some more formal view about this
question.
Many thanks!
Jean-Marc
Le 09/03/2021 à 20:42, Ling Chan a écrit :
This is the continuation of the previous reply, to elaborate on "the
stripped structure can always be represented using wedged bonds".
One potential problem is that a bond is required to be wedged from
both ends. But this should not happen. For an atom to be chiral, it
needs to be attached to at least 3 other atoms. If it is attached to 3
atoms, its chirality can be specified by using a wedge on any one of
the three bonds. Hence there should always be enough possibilities to
avoid the potential problem.
I could be wrong. I can't proof it. But this is what it feels like to
me, especially if no atom is bonded to more than 4 other atoms.
Ling Chan <lingtrek...@gmail.com <mailto:lingtrek...@gmail.com>> 於
2021年3月9日週二 上午11:32寫道：
Hello Jean-Marc,
This is a very interesting question.
Given any molecule, consider its structure stripped of all H's.
There is no reason why this stripped structure cannot be
represented using wedged bonds etc. (Will continue on the next
reply.) Hence potential problems can only arise when the added Hs
themselves introduce new chirality / stereochemistry, or that the
position of the added H itself is not uniquely defined by the
stripped structure.
One example I can think of is the secondary amine, if you only
consider one state (say if the temperature is so low that it is
locked in that geometry). But if there is a rule saying that "the
implicit hydrogen is understood to lie in the plane of the paper",
then everything will still be fine. Just that the drawings may
look a bit strange, as attached.
But for stereo bonds, perhaps there is no escape. You will need to
draw the explicit hydrogen. See attached.
But then how about the orientation of hydroxyl groups in general?
They are usually neglected in chemical representations, aren't they??
Ling
Jean-Marc Nuzillard <jm.nuzill...@univ-reims.fr
<mailto:jm.nuzill...@univ-reims.fr>> 於 2021年3月9日週二
上午1:04寫道：
Sure, testosterone may be drawn as
Jean-Marc
Le 08/03/2021 à 18:26, Rocco Moretti a écrit :
On Mon, Mar 8, 2021 at 11:17 AM Paul Emsley
<pems...@mrc-lmb.cam.ac.uk
<mailto:pems...@mrc-lmb.cam.ac.uk>> wrote:
On 08/03/2021 13:55, Jean-Marc Nuzillard wrote:
>
> Is it always possible to represent an organic molecule
in 2D with all necessary
> configuration hints (bond wedges pointing to the front
or to the back)
> without introducing any explicit hydrogen atom?
No. Testosterone.
Is that "not possible" or simply "against convention"? One
could certainly imagine someone attempting to put the dashed
and wedged designations on the ring bonds, and leaving the
hydrogens implicit. (Flagrantly ignoring how much it would
mess with steroid chemists' brains.)
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Jean-Marc Nuzillard
Directeur de Recherches au CNRS
Institut de Chimie Moléculaire de Reims
CNRS UMR 7312
Moulin de la Housse
CPCBAI, Bâtiment 18
BP 1039
51687 REIMS Cedex 2
France
Tel : 03 26 91 82 10
Fax : 03 26 91 31 66
http://www.univ-reims.fr/icmr
http://eos.univ-reims.fr/LSD/CSNteam.html
http://www.univ-reims.fr/LSD/
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