I'm pretty sure that both C bonded to N are stereogenic centers. I don't know about the others, any help? Is this correct?
$\begingroup$
$\endgroup$
3
-
5$\begingroup$ I think there is only one chiral center in atropine. $\endgroup$– Curt F.Jul 14, 2021 at 16:54
-
1$\begingroup$ @Curt F.: The ring is symmetric so all three carbon centers shown in are not chiral. The sole chiral center is the $\alpha$-carbon to carbonyl group. $\endgroup$– Mathew MahindaratneJul 14, 2021 at 17:01
-
$\begingroup$ Hi, actually I meant stereogenic center, I don't know if it's different from the definition of chiral center. $\endgroup$– Silvia95Jul 14, 2021 at 20:34
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
I assume the OP means atropine in which case the structure presented has an extra methylene group. The renderings of a single enantiomer of atropine by ChemDraw 20.1 and JSmol are shown below.
Using the terminology of Mislow and Siegel (https://doi.org/10.1021/ja00323a043), the bridgehead carbons and the benzylic carbon are stereogenic and chirotopic, Thus, the R/S designation. The remaining carbon labeled "r" is stereogenic but achirotopic (r/s). Therefore, there are four stereogenic centers three of which are chirotopic.
answered Jul 14, 2021 at 22:49
$\begingroup$
$\endgroup$
6
In this question you can look at the IUPAC definition of the chiral center. According to the definition, carbons that are attached to nitrogen are chiral centers — they have 4 different chemical groups attached to them. The $\alpha$-carbon to the ester group is also a chiral center. However, the third carbon (from top to bottom) that you circled is not a chiral center because two groups from the cycle are identical.
-
1$\begingroup$ Yes, nevertheless, the "third carbon" is a pseudoasymmetric center (r or s). $\endgroup$– LoongJul 14, 2021 at 18:18
-
1$\begingroup$ IUPAC defines chirality centre (doi.org/10.1351/goldbook.C01060) as An atom holding a set of ligands in a spatial arrangement which is not superposable on its mirror image. That doesn't necessarily mean that it has to be four different groups, although that is a convenient rule of thumb. $\endgroup$– Martin - マーチン ♦Jul 14, 2021 at 18:23
-
$\begingroup$ @Loong you're right but question asks for chiral centers $\endgroup$– AzamatJul 14, 2021 at 18:31
-
$\begingroup$ @Martin-マーチン in definition that you referred to it's written Cabcd. And it's also written that this is a generalization of concept of asymmetric carbon atom which is defined as I wrote (doi.org/10.1351/goldbook.A00479). If I am wrong somewhere, please correct me. $\endgroup$– AzamatJul 14, 2021 at 18:35
-
$\begingroup$ Hi, actually I meant stereogenic center, I don't know if it's different from the definition of chiral center. $\endgroup$– Silvia95Jul 14, 2021 at 20:31