Comments on: Ranking The Bulkiness Of Substituents On Cyclohexanes: “A-Values”

By: Cyclohexane Chair Conformation Stability: Which One Is Lower Energy? | Straight A Mindset

Thu, 07 Dec 2023 22:12:07 +0000

[…] In the last post, we introduced A values and said they were a useful tool for determining which groups are “bulkiest” on a cyclohexane ring. (See post: Ranking the Bulkiness Of Substituents On Cyclohexane Rings With A-Values) […]

By: Ranking The Bulkiness Of Substituents On Cyclohexanes: “A-Values” | Straight A Mindset

Thu, 07 Dec 2023 22:10:23 +0000

[…] Hydroxyl (OH) (0.87 kcal/mol) […]

By: Umang Singh

Umang Singh — Fri, 24 Sep 2021 10:19:23 +0000

Thanks for your response and I am also not getting any relevant information for this, by the way thanks for helping, can i get your contact information, if yes my e-mail is attached.

By: James Ashenhurst

James Ashenhurst — Thu, 23 Sep 2021 21:41:36 +0000

In reply to Umang Singh.

Winstein defined it in 1955 as the free-energy preference of a substituent for the equatorial position. It was defined in this paper. I’m not sure use of the letter A refers to any physical property however. (I don’t have access to this paper otherwise I’d try to give you more information).
https://pubs.acs.org/doi/abs/10.1021/ja01626a037?journalCode=jacsat&quickLinkVolume=77&quickLinkPage=5562&selectedTab=citation&volume=77

By: Umang Singh

Umang Singh — Thu, 23 Sep 2021 05:49:13 +0000

Thank you for the nice explanation,
I want to ask what does ‘A’ means in A-value, why is it called A-value?

By: James Ashenhurst

James Ashenhurst — Tue, 16 Jun 2020 03:55:33 +0000

In reply to Mia Lehavi. Isopropyl: 2.15 , propyl is similar to ethyl, around 1.75

By: Mia Lehavi

Mia Lehavi — Mon, 15 Jun 2020 23:06:25 +0000

Hello,
This is a great explanation, thank you! How would you compare the A-values between isopropyl and propyl? Thanks so much!

By: James Ashenhurst

James Ashenhurst — Sat, 30 May 2020 02:14:56 +0000

In reply to Rimsha Mujahid. These come from experimental measurement. At some point in the near future I'll include references.

By: James Ashenhurst

James Ashenhurst — Sat, 30 May 2020 02:14:19 +0000

In reply to Jake. Fixed. Thanks for the heads-up

By: James Ashenhurst

James Ashenhurst — Sat, 30 May 2020 02:14:10 +0000

In reply to kc. Fixed - thank you so much.