Princess Kawaii
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Can someone help please...how do I start off with this question

"Suggest a synthesis of procaine from Benzocaine"

:confused:
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Qwertish
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(Original post by Princess Kawaii)
Can someone help please...how do I start off with this question

"Suggest a synthesis of procaine from Benzocaine"

:confused:
Oh, that's a hard one...

First off, find out what Benzocaine and procaine are.

Benzocaine is ethyl 4-aminobenzoate
Procaine is 2-(diethylamino)ethyl 4-aminobenzoate

You'd first need to synthesize diethylamine, and then substitute this onto the end of the ethyl group in Benzocaine.

The first bit's pretty straightforward (bromoethane, created by electrophilic addition of HBr to ethene, heated with ammoina).

I've no idea how you'd go about doing the second step (the substitution) though. It would be a nucleophilic substitution, so presumably you'd first need to add a bromine to the end of the ethyl group, to make it 2-bromoethyl 4-aminobenzoate. That's the bit I'm stuck on. I don't know how one could go about targeting that specific carbon atom, otherwise you'd get a mixture of 1-bromoethyl 4-aminobenzoate and 2-bromoethyl 4-aminobenzoate...

EDIT:
I guess you could just do a free radical substitution of bromine onto Benzocaine, and then separate out all the different products, leaving only 2-bromoethyl 4-aminobenzoate (the one you want). Then do a nucleophilic substitution of of diethylamine onto 2-bromoethyl 4-aminobenzoate.
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Omelette
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Hydrolyse, then esterify. Don't make it more complicated than it has to be.
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Qwertish
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(Original post by Omelette)
Hydrolyse, then esterify. Don't make it more complicated than it has to be.
Lol. Yes. Do this.

Hydrolyse to get rid of the ethyl group and make 4-aminobenzenecarboxylic acid.

Then make triethylamine, then add an -OH to one of the ethyl groups to make N-(2-hydroxyethyl)diethylamine, then esterify.
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illusionz
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(Original post by Qwertish)
Then make triethylamine, then add an -OH to one of the ethyl groups to make N-(2-hydroxyethyl)diethylamine, then esterify.
Not a very simple reaction...
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Qwertish
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(Original post by illusionz)
Not a very simple reaction...
How about diethylamine. Then make dibromoethane from ethene and Br2, and then do a nucleophilic subs of OH- to make 2-bromoethan-1-ol, then nucleophilic subs of diethylamine and 2-bromoethan-1-ol.
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illusionz
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(Original post by Qwertish)
How about diethylamine. Then make dibromoethane from ethene and Br2, and then do a nucleophilic subs of OH- to make 2-bromoethan-1-ol, then nucleophilic subs of diethylamine and 2-bromoethan-1-ol.
I don't know know what level you are at... but using a secondary amine in nucleophilic substitution is a bad idea as the product is more reactive than the reagent, so you get further reaction.

I would use diethylamine, react 1:1 ratio with Glyoxal and catalytic acid to form an imine on one of the carbons, then reduce with NaBH4 to form the compound you want (reduces imine to amine and reduces aldehyde to alcohol).
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Qwertish
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(Original post by illusionz)
I don't know know what level you are at... but using a secondary amine in nucleophilic substitution is a bad idea as the product is more reactive than the reagent, so you get further reaction.

I would use diethylamine, react 1:1 ratio with Glyoxal and catalytic acid to form an imine on one of the carbons, then reduce with NaBH4 to form the compound you want.
A level :P. I know the product is a more reactive nucleophile than the reactant (inductive effect of the alkyl groups)

I don't know what level at OP is at, but at A level, it's fine for us to assume that the correct product can be separated (at least on AQA).
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