Co2

[chiddler]

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So can we only remove carboxylic acids from compounds as CO2 when the compound is a malonic ester?

 

[MedPR]

So can we only remove carboxylic acids from compounds as CO2 when the compound is a malonic ester?

Orgo isn't my strong point, but I'm going to venture a guess that the carboxyl group always leaves as CO2 (decarboxylation).

 

[hopeful22213]

You can readily lose a CO2 in all beta-keto acids.

 

[chiddler]

ok then what's going on here. i was looking for butane but it wasn't even an answer choice.

therefore, there must be some proximal carboxylic acid group?
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yeah i'm right about this because of another question tbr asks.

ok thanks i'm happy.

 

[MedPR]

ok then what's going on here. i was looking for butane but it wasn't even an answer choice.

therefore, there must be some proximal carboxylic acid group?
--
yeah i'm right about this because of another question tbr asks.

ok thanks i'm happy.

You originally asked about removing a carboxylic acid, but in this reaction there is no removal of a carboxylic acid. I'm confused 😕

 

[chiddler]

i was confused why CO2 wasn't evolved.

the reason is that there must be another nearby carboxylic acid group for this to be possible. so in this case, the heat and acid served other purposes. it was to acidify the carboxylic acid, i guess. but i'm really clueless why heat was necessary.

 

[pfaction]

Wouldn't acid and heat form an acid anhydride?

Here's what could have happened?

MgBR is on the O-, which requires acid to protonate it.

But heat...acids and heat should produce anhydrides (assuming this isn't a one molecule thing).

 

[chiddler]

dehydration produces anyhydrides. heat is one way to do it but heat is not necessarily dehydration.

 

[MedPR]

Oh I see now. I guess it does make sense that decarboxylation would only occur in malonic acid or structures like malonic acid (beta-ketoesters, etc). Otherwise it's just a rearrangement as you show above.

 

[chiddler]

Oh I see now. I guess it does make sense that decarboxylation would only occur in malonic acid or structures like malonic acid (beta-ketoesters, etc). Otherwise it's just a rearrangement as you show above.

not a rearrangement!

same thing just drawn differently. i know it's not plainly visible, I had to draw it out for myself initially. the reason I did that is to show it exactly as TBR drew it in case i was missing something.

 

[pfaction]

dehydration produces anyhydrides. heat is one way to do it but heat is not necessarily dehydration.

Okay because TPR says dehydrate and heat. My figuring was it didnt state dehydrate, but it had the protonation of the O--MgBr and heat so I thought anhydride.

Whats going on in the reaction now?