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Topic: Silyl enol ethers - a doubt...  (Read 582 times)

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Offline xshadow

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Silyl enol ethers - a doubt...
« on: August 26, 2019, 04:45:17 PM »
HI
:)
I don't understand too much the silyl enol ether formation


Why if I have an Enolate + TMSC (CH3SiCl) the enolate attacks the Si using his O -electrons

I usually have seen an enolate  - acting as a nucleophile- attacking an electrophilic atom (like C=O
) with the C carbon atom of enolate...the bond is created between the nucleophilic carbon of an enolate and the electrophilic atom , for example a C- carbonyl


Now here I have that the nucleohilic enolate bond with Si of TMSC through the O-enolates atom ...and NOT the C-enolates atom

Why??!

Thanksss so much :)

Offline rolnor

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Re: Silyl enol ethers - a doubt...
« Reply #1 on: August 27, 2019, 12:32:53 AM »
The silylhalide is a hard electrophile and reacts with the hard nucleophile oxygen. The enolate carbon is a soft electrophile.
Here is a link with nice info about this topic:

https://youtu.be/04NYWxuD6d4
« Last Edit: August 27, 2019, 03:19:42 AM by rolnor »

Offline xshadow

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Re: Silyl enol ethers - a doubt...
« Reply #2 on: August 27, 2019, 07:38:02 PM »
Saw the video but I have some doubt about hard and soft

For example:

PH3 vs NH3 ....I think that PH3 is a softer base/nucleophile  than NH3 because the donor atom,P,is larger than N

N3- vs NH2-

Here I don't understand which one is softer ...
Some help? N is the donor atom and in both I have a negative charge
Thankss!
« Last Edit: August 27, 2019, 07:53:39 PM by xshadow »

Offline rolnor

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Re: Silyl enol ethers - a doubt...
« Reply #3 on: August 28, 2019, 04:57:37 AM »
I think the video is about giving you a generall idea about the concept, not quantifying exactly the nucleophiles being softer or harder.

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