No, prochiral atoms have the same rank. Your question got me thinking to
how we could detect prochiral atoms, here is the stupidest/simplest
solution I could come up with, it changes isotopes on every atom until a
new chiral center is added, this atom is considered prochiral:
def numUnspecifiedStereoAtoms(mol):
"""Return the number of unspecified stereo atoms in a molecule"""
return len([atom for atom in mol.GetAtoms() if
("_ChiralityPossible" in atom.GetPropNames() and
atom.GetChiralTag() ==
Chem.rdchem.ChiralType.CHI_UNSPECIFIED)])
def findProchiral(m):
"""Return indices of prochiral atoms, to find prochiral hydrogens,
hydrogens must appear in the graph, see Chem.AddHs"""
indices = [ atom.GetIdx() for atom in m.GetAtoms() ]
tags = [atom.GetChiralTag() for atom in m.GetAtoms()]
num_unspecified = numUnspecifiedStereoAtoms(m)
prochiral = []
for index in indices:
m2 = Chem.Mol(m)
m2.GetAtomWithIdx(index).SetIsotope(2)
m3 = Chem.MolFromSmiles(Chem.MolToSmiles(m2, isomericSmiles=True))
if numUnspecifiedStereoAtoms(m3) != num_unspecified:
prochiral.append(index)
return prochiral
print findProchiral(Chem.AddHs(Chem.MolFromSmiles("C1C(C(N)=O)=CNC=C1")))
On Thu, Mar 10, 2016 at 11:30 AM, Peter S. Shenkin <[email protected]>
wrote:
> Is the canonical rank of prochiral H's different or the same? (For example
> the rank of the H's on C-1 of ethyl chloride.)
>
> Thanks,
> -P.
>
>
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