Comments on: Chiral Allenes And Chiral Axes

By: James Ashenhurst

James Ashenhurst — Thu, 12 Sep 2024 17:19:27 +0000

In reply to karan.

For molecules with an axis of chirality, one looks along the chiral axis and numbers the substituents on the near carbon (1) or (2) according to the CIP rules. One then looks at the substituents on the far carbon and numbers them (3) or (4) according to the CIP rules. One then notes whether 1,2,3 goes clockwise (r) or counterclockwise (s). See this article (wikipedia) for an example:
https://en.wikipedia.org/wiki/Axial_chirality

By: karan

karan — Tue, 10 Sep 2024 03:58:50 +0000

can we assign R and S nomenclature for 3 cumulative diene between 4 carbon atoms. for eg C=C=C=C type systems.

By: James Ashenhurst

James Ashenhurst — Fri, 10 May 2024 17:02:49 +0000

In reply to Aman Aryatosh. Yes, that's a valid answer

By: Aman Aryatosh

Aman Aryatosh — Fri, 10 May 2024 07:17:33 +0000

So can we generalize the fact that if the number of double bonds are even with different groups at the ends then the molecule has to be achiral?

By: James Ashenhurst

James Ashenhurst — Thu, 09 Nov 2023 17:11:19 +0000

In reply to Zeri. No, it is referred to as a chiral axis since chirality is not confined to the configuration of a single carbon. Kind of like how a screw is chiral (left handed or right handed) but you can't pinpoint an individual center of chirality; instead, it has an axis of chirality as well.

By: Zeri

Zeri — Thu, 09 Nov 2023 06:40:47 +0000

Does a chiral allene contain stereogenic centres? Can we say that the two carbons at the ends are the stereogenic centres?

By: James Ashenhurst

James Ashenhurst — Thu, 13 Oct 2022 18:31:29 +0000

In reply to Madiha zeb. See bottom of post.

By: Madiha zeb

Madiha zeb — Thu, 13 Oct 2022 10:41:29 +0000

( H cl c=c=c=c H cl ) absolute configuration of it . And why it is optically inactive

By: James Ashenhurst

James Ashenhurst — Mon, 08 Nov 2021 21:26:47 +0000

In reply to Richard Aversa. Darnit. Will fix. Thank you Rich. [EDIT: fixed]

By: Richard Aversa

Richard Aversa — Sat, 06 Nov 2021 00:30:47 +0000

Great work as always James. In Section 4, right after the line “Now: what happens if we add a second group to the same carbon?” you show a disubstituted allene structure with two Cl substituents on different ends of the allene, when I believe you meant to show them on the same carbon (to represent an achiral disubstituted allene). Keep up the good work.