Comments on: Alkenes To Alkynes Via Halogenation And Elimination Reactions

By: Madhav Mittal

Madhav Mittal — Thu, 09 May 2024 11:42:44 +0000

Should not the dehydrohalogenation of alkenyl halide be E1CB instead of E2?
I am saying so because the leaving group will become poor due to partial double bond character.

By: Mohit Ram

Mohit Ram — Mon, 30 Nov 2020 02:46:23 +0000

Hey brother, I’m totally confused. Please reply anyone if you know solution of my query!
First of all, talking about – ve charged species. It’s nucleophile cum base”(depending upon its attacking group). You treated alkane alkenes with NaNH2. Here this acts NaNH2 acts as an base, which deprotonates the substrate giving elimination product. Also, using NaOH(OH^-) when treated with substrate (mostly alkane derivatives) gives substitution reactions, whereas the same NaOH, acts as a base for the substrate, like in above bromoalkene did (when treated with NaOH gives alkynes… an elimination product). So I totally don’t understand where this types of reagents are going to act as BASE and when NUCLEOPHILE.
Please anyone help me, I’ve asked this question many a times to other, but none of them were able. This was the reason for my hate for organic. But, I want to grow up once again. Please help… This is my building organic concept for JEE ADVANCED.

By: James Ashenhurst

James Ashenhurst — Wed, 11 Nov 2020 18:09:08 +0000

In reply to Mia. It can be done with either. However, NaNH2 is a stronger base so it can be done under less forcing conditions this way.

By: Mia

Mia — Sun, 08 Nov 2020 20:00:08 +0000

We can also use alcoholic KOH for dehydrohalogenation of vicinal dihalide right?But from what I have seen sodamide is preferred why is that so?

By: James Ashenhurst

James Ashenhurst — Sat, 29 Jun 2019 02:12:53 +0000

In reply to Jay. By "NaNH3" I think you mean Na/NH3 which is the reduction of an alkyne with sodium in ammonia. This will reduce an alkyne to a trans alkene.

By: Prakash

Prakash — Thu, 09 May 2019 08:50:58 +0000

In reply to B. For E2 reaction you need only a strong base not a bulky one. A bulky base can lead to Hoffman product instead of zaitsev product.

By: Minhas

Minhas — Sat, 30 Jun 2018 10:05:03 +0000

In reply to XYZ. Yes you are right

By: Jay

Jay — Sat, 28 Jan 2017 15:36:24 +0000

Will the reaction be the same if NaNH3 is used instead of NaNh2 with an alkyl dihalide?

By: ABC

ABC — Wed, 02 Nov 2016 13:21:32 +0000

In reply to XYZ. YES

By: XYZ

XYZ — Thu, 21 Jan 2016 15:12:12 +0000

When NaNH2 is added in excess is the reaction E1cB as there is carbanion? ? Am I right? Please clear up my misunderstanding. Thank You.