Which is more reactive in nucleophilic acyl substitution: Thioester or Ester?

[CANgnome]

title says it all 🙂


Just been wandering since doing this destroyer question.

It listed acyl halide > anhydride > thioester > amide > ether

I know esters are in between anhydride and amide too, but which is more reactive, thioester or ester?


also, how is the reactivity of ether compared to carboxylic acids? better or worse?


I am thinking since oxygen is more electronegative, it can hold negative charges better, so esters are more reactive than thioesters.

I am thinking that carboxylic acids are more reactive than ethers too, since alkyl is electron donating? I doubt this will be on the Dat though, maybe the thioester one.

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[wantVCUdental]

but which is more reactive, thioester or ester?
In nucleophilic acyl reactions i think ester is more reactive than thioesters since the carbon of the carbonyl group is going to be more d+, due to a greater electronegativity difference between carbon and oxygen.
Whereas the sulfur is more electronegative than carbon, so it'll be less reactive.



also, how is the reactivity of ether compared to carboxylic acids? better or worse?
I think for the same reason, carboxylic acids are more reacitve than ether... 2O>1O 😀

SO YES, you are correct 😀

 

[CANgnome]

Thioester is

R-(C=O)-S-R while ester is R-(C=O)-O-R

so they both have a carbonyl carbon 😕 perhaps the oxygen is more electronegative than sulfur and so makes the carbonyl carbon more d+


i just think that esters are not too reactive regardless. I only remember the ester cleavage and williamson and that seem to be all esters are good for.

 

[chromosome21]

1. ester
2. carboxylic acid

 

[orgohacks]

title says it all 🙂


Just been wandering since doing this destroyer question.

It listed acyl halide > anhydride > thioester > amide > ether

I know esters are in between anhydride and amide too, but which is more reactive, thioester or ester?


also, how is the reactivity of ether compared to carboxylic acids? better or worse?


I am thinking since oxygen is more electronegative, it can hold negative charges better, so esters are more reactive than thioesters.

I am thinking that carboxylic acids are more reactive than ethers too, since alkyl is electron donating? I doubt this will be on the Dat though, maybe the thioester one.

thioester reactivity > ester, because the RS- leaving group better than RO-. RSH is a stronger acid than ROH . (pKa of ~12 vs. ~17).

carboxylic acids are difficult to compare, since they need acid to undergo substitution. With a base, you'll just deprotonate the carboxylic acid to give RC(O)O- , and the O- is never going to leave.

ethers are pretty much completely unreactive except under very harsh conditions.

hope this helps - James

 

[viresh]

Why are esters less reactive than anhydrides?

 

[njohns24]

*

 

[ToBeDDSS]

The thirster is more reactive because it has less resonance stabilization.

 

[johadd]

The thioester obviously.
The sulfur is a bigger atom and less electronegative than oxygen therefore it holds it's electrons more loosely and therefore more reactive.

Hope this helps

I got it from the destroyer, it explains it in the back by one of the questions.
Review it