Comments on: Electrophilic Aromatic Substitution – The Mechanism

By: James Ashenhurst

James Ashenhurst — Tue, 07 Feb 2023 18:12:27 +0000

In reply to zey. There are two ortho positions and only one para position. So if it were completely random (and there were no meta) the yield would be 66%. The fact that the yield is 57% shows that the methyl group has some steric influence. The effect becomes much greater as the alkyl group is increased in size.

By: zey

zey — Tue, 07 Feb 2023 14:18:40 +0000

hello, thank you first! i have a question, in the example of methyl benzene, why did the reaction give the product where nitro group is in ortho position in a greater yield than the one where it is in para position?

By: James Ashenhurst

James Ashenhurst — Wed, 31 Aug 2022 19:11:34 +0000

Have you seen the section on EAS from “Modern Physical Organic Chemistry” (p. 608) by Anslyn? The description is quite clear. In most cases the reaction will be second-order overall, but when there is a bulky group (e.g. t-butyl) the rate of the reverse reaction can be significant. In those cases the reverse reaction starts to have about the same barrier as the rate of deprotonation, which leads to secondary isotope effects.

By: Ankit

Ankit — Fri, 26 Aug 2022 17:59:18 +0000

Hey! Great post however a few questions come to my mind from the texts I have. They have been great and clear but how primary isotopic effects and secondary isotopic effects are affected by the bulkiness of the electrophile have not been described very clearly, and other texts don’t seem have any information of them.

It mentions that primary isotopic effect is seen when the loss of an alpha-hydrogen happens in the slower than the formation of the Wheland-complex. It says this is only the case when the electrophile is a significantly bulkier group.

I’d also like to know how charge-transfer complexes are formed from pi-complexes, but that is a little off-topic and at the risk of digressing I wont talk too much about them (I dont understand them well enough anyway)

By: Satti

Satti — Mon, 23 May 2022 18:11:48 +0000

Assalam o alaikum.very good explanation sir.i enjoyed a lot reading it because it is giving me strong concepts.much helpful!!
I appreciate sir.

By: Reattività del benzene – Appunti Liceo Università

Reattività del benzene – Appunti Liceo Università — Mon, 28 Mar 2022 06:28:28 +0000

[…] Figura 2: energetica della sostituzione elettrofila aromatica. Si noti come la formazione del carbocatione sia il RDS, in quanto il corrispondente stato di transizione è nel massimo assoluto di energia. La velocità del processo aumenta al crescere della stabilità del carbocatione intermedio, per il postulato di Hammond. (Foto di Master Organic Chemistry) […]

By: 1.0 INTRODUCTION – ORGANIC COMPOUNDS

1.0 INTRODUCTION – ORGANIC COMPOUNDS — Wed, 16 Jun 2021 16:48:44 +0000

[…] Ortho, Para, and Meta Directors Electrophilic Aromatic Substitution – The Mechanism Ortho-, Para- and Meta- Directors in Electrophilic Aromatic […]

By: Electrophilic Aromatic Substitution: Definition, Examples & Mechanism

Electrophilic Aromatic Substitution: Definition, Examples & Mechanism — Tue, 18 Feb 2020 10:02:09 +0000

[…] Mechanism – Masterorganicchemistry.com […]

By: James Ashenhurst

James Ashenhurst — Mon, 30 Sep 2019 19:17:48 +0000

In reply to Piyush. There is only one intermediate - the carbocation. Are you referring to the two transition states?

By: Piyush

Piyush — Sun, 29 Sep 2019 16:34:19 +0000

The energy of second intermiediate is more than first in the given energy diagram? ….