JEE Chemistry Club

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sai-kartik

02:53

@GuruVishnu can you show your intermediate please?

i dont see how a tertiary carbocation can be formed... besides, we always get gem di halides on addition of HX to an alkyne. This is a rather common question in jee too...

i dont think vinylic cations can even rearrange until there is scope for resonance

@Safdar What's your take on this?

1 hour later…

Guru Vishnu

04:23

@sai-kartik Hi! I hope you would be able to take from here:

After this, an iodide ion attacks the tertiary carbocation. Then with the second equivalent of hydrogen iodide, a Markovnikov addition takes place giving the product I got.

I think, now I found a method to arrive at the book's answer even after rearrangements:

So, the product I arrived at first might be incorrect. Even after two rearrangements (as given above), we get the same product without any rearrangement (as done in the book).

1 hour later…

Yuvraj

05:42

@GuruVishnu it would only be in excess

sai-kartik

@GuruVishnu haven't seen this rearrangement anywhere 😬

1 hour later…

Safdar

06:55

@sai-kartik I wouldn't be online 90% if the time.. I just have it open on another tab.. so pinging me isn't the best idea

7 hours later…

Safdar

14:05

$$\mathrm{ Propanoyl Chloride}\ce{ ->[NH2OH][\text{ethanoyl chloride}/H2O,\Delta] X}$$

@YusufHasan

satan 29

14:17

@GuruVishnu yes! this is my doubt also

And unfortunately solomons-frhyle-snyder has no mention of the mechanism

Although My JEE notes say :"gem di-halides are formed"

Guru Vishnu

@satan29 Are you having the Indian version (adapted by MS Chouhan) or International version?

satan 29

adapted by MS chouhan

Guru Vishnu

Then it must be there somewhere after Prins reaction.

satan 29

lemme see

Guru Vishnu

Did you (@satan29) and @sai-kartik see this:

10 hours ago, by Guru Vishnu

This seems to be inline with your notes and also the final product given in the book.

That second rearrangement takes place for a reason the carbocation is stabilized by the +M effect of iodine. But if I recall correctly that must be applicable only for chlorine.