Comments on: How To Use Curved Arrows To Interchange Resonance Forms

By: Anuj Kshirsagar

Anuj Kshirsagar — Sat, 10 Aug 2024 03:48:06 +0000

The interactive reaction animations are fantastic! They are incredibly helpful for understanding the concepts. Thank you for providing all this valuable content for free!

By: Can A Curved Arrow Begin At A Pi Bond?

Can A Curved Arrow Begin At A Pi Bond? — Fri, 08 Sep 2023 01:08:10 +0000

[…] How To Use Curved Arrows To Interconvert Resonance Forms […]

By: James Ashenhurst

James Ashenhurst — Thu, 21 Nov 2019 03:18:58 +0000

In reply to sarah. It's actually a CH2+ . Hopefully an updated drawing will make it more clear.

By: sarah

sarah — Wed, 23 May 2018 03:20:53 +0000

Hello!

I really don’t understand how C3 went from CH3 to CH2 with a double bond, and the + charge remains localized on C1. Please explain and thanks so much in advance.

By: lmb

lmb — Wed, 12 Feb 2014 03:21:15 +0000

This is fantastic. Clears up a lot of dumb mistakes I could have avoided in Orgo 1. This semester will be better! Thanks so much James!

By: irhunt

irhunt — Fri, 25 May 2012 15:56:14 +0000

I agree that hyperconjugation is a “possible” example of resonance ( a special case). However, I don’t like the example you cite because it is really an E2 reaction. I see the area you are dealing with (the gauche effect) and why you might like to call it resonance. Anyway, I’d make the case that it does involve pi systems because the one form contains a new pi bond.
But why not just call it hyperconjugation which can it’s own unique characteristics that can be used to keep it distinct ? I think that can only help students of organic chemistry in the long run.
The FCH2CH2F certainly is an interesting example. I just looked at a few references to check C-F bonds lengths…. for 1,2-difluoroethane Xray data gave 1.39A. A general list of typical sp3C-F data cited 1.4A. At a first assessment this rationale for the geometric preference might be flawed because it doesn’t seem to rationalise the C-F bond length trend correctly.

By: mevans

mevans — Wed, 18 Apr 2012 14:54:40 +0000

In reply to james.

Gak; My fault. Let’s try that again, with a more useful example. Don’t mean to start a flame war.

http://imgur.com/q9yfi

Hyperconjugation (or “double-bond no-bond resonance”) is the idea; the point is that hyperconjugation is really just a fancy form of resonance. When the applications are structural (conformation, bond lengths/angles, etc.) it can be called resonance because the electron flow doesn’t really reflect chemical change—it helps us explain structural reality.

By: james

james — Wed, 04 Jan 2012 22:38:38 +0000

In reply to mevans. That drawing has an error, it should have a pi bond in it. And it seems like either an example of an E2 or of hyperconjugation....

By: irhunt

irhunt — Mon, 05 Dec 2011 02:08:19 +0000

In reply to mevans. Poppycock? Give me an example of resonance that is not about pi electrons or pi bonds then ?

By: james

james — Fri, 02 Dec 2011 03:58:05 +0000

In reply to mevans. That's next (with simple examples first)