Ester to acid chloride transformation

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    Organic chemistry
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Discussion Overview

The discussion revolves around the transformation of esters to acid chlorides, specifically comparing two synthetic pathways: one that is base-catalyzed and another that is acid-catalyzed. Participants explore the implications of using different protecting groups and the stability of those groups under varying pH conditions.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents two synthetic options for the transformation, noting that both involve hydrolyzing the ester to a carboxylic acid before converting it to an acid chloride using SOCl2.
  • The participant claims that option A is the correct pathway but expresses confusion about why option B is considered worse.
  • Another participant mentions that the stability of silyl ethers may be pH dependent, suggesting a potential issue with the acid-catalyzed pathway.
  • A different participant references a source indicating that the reaction with acids can remove the silyl group, implying that this is a known characteristic of the protecting group used.
  • One participant asserts that the protecting group in option B is acid sensitive, arguing that the second step in B undermines the first step.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of the acid-catalyzed pathway compared to the base-catalyzed pathway, with no consensus reached on the reasons for the perceived shortcomings of option B.

Contextual Notes

There is uncertainty regarding the stability of silyl ethers under different pH conditions and how this affects the overall reaction pathways. The discussion also highlights a lack of clarity in available resources regarding these reactions.

jolly_math
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Homework Statement
Which best accomplishes the following transformation?
Relevant Equations
ester to acid chloride
1712982333579.png


Here are 2 options:
A)
1712982413712.png
B)
1712982432602.png


For both syntheses, a protecting group is added to the alcohol, the ester is hydrolyzed to a carboxylic acid, then it is turned into an acid chloride using SOCl2. The difference is that A is base-catalyzed and B is acid-catalyzed.

The correct answer is A, but I don't understand why B doesn't work or is worse than A.

Thank you.
 
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Eons passed since I worked with these things, but quick googling for stability of silyl ethers seems to be suggesting it is pH dependent.
 
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Borek said:
Eons passed since I worked with these things, but quick googling for stability of silyl ethers seems to be suggesting it is pH dependent.
I've never seen this in my textbook or the resources I've used so far though. Is this a commonly-known fact?
 
Even wiki states: "Reaction with acids (...) removes the silyl group when protection is no longer needed.", so my bet is yes, it is something quite well known.
 
This protection group is acid sensitive. Step 2 in B negates step 1.
 

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