DAT Destroyer Q Orgo

[nayryecal]

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Hi
#255 on 2013 Dat Destroyer-its a deickman condensation reaction. The first step uses NaOC2H5 as a base and the second step says H30+. I understand how the first step works and how it closes to make a ring. But why doesn't the H30+ in the second step turn the ester into a carboxylic acid? What does that H30+ do?

 

[MikeQ]

Hi
#255 on 2013 Dat Destroyer-its a deickman condensation reaction. The first step uses NaOC2H5 as a base and the second step says H30+. I understand how the first step works and how it closes to make a ring. But why doesn't the H30+ in the second step turn the ester into a carboxylic acid? What does that H30+ do?

Have you watched Chads videos?

If not there is an order of reactivity when it comes to carboxylic acids and there derivatives. Acyl chloride being most reactive then anhydride, ester, amide, and carboxylate being least reactive [worst leaving group]. The way this works, if you start with acyl chloride COCl, you can turn it into anything going down the trend simply by adding the the new part. This means, COCl -> COOCH3 [ester] all you have to do is add the new addition which is OCH3 to the acyl halide. So now you can turn the ester into anything below meaning less reactive such as an amide by simply adding NH2. Now you can never go up meaning turning the amide into ester directly or tuning ester into anhydride because it will be turning something with a bad leaving group into something with a better leaving group. With all this being said to answer your question you can turn any one of the five [acyl chloride, anhydride, ester, amide, carboxylate ion] directly into a COOH simply by adding acid, H3O. H3O will attack the carbonyl replacing the better leaving group, in your case ester, with an OH which is a horrible leaving group. I hope this helped tried my best to explain it on my phone. Ask away if you still dont understand.