August 22, 2019, 01:09:22 AM
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Topic: Organic chemistry reactions from 4-hydroxybutanoic acid to threonine  (Read 120 times)

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Offline cyanzi

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The question says  to devise a scheme to prepare threonine from 4-hydroxybutanoic acid (HOCH2CH2CH2COOH)

So far, I've done this:
HOCH2CH2CH2COOH :rarrow: Br2/LDA  :rarrow: HOCH2CH2CHBrCOOH  :rarrow: conc. H2SO4 :rarrow: H2C=CHCHBrCOOH :rarrow: H+/H2O :rarrow: CH3CHOHCHBrCOOH :rarrow: NH3(alc) :rarrow: CH3CHOHCHNH2COOH
But apparently this is incorrect (I seem to have gone wrong at the 3rd step going from H2C=CHCHBrCOOH :rarrow: CH3CHOHCHBrCOOH)
What exactly is wrong?

Offline AlirezaDehghani

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Re: Organic chemistry reactions from 4-hydroxybutanoic acid to threonine
« Reply #1 on: August 03, 2019, 05:10:25 AM »
Hi
your second step involves the formation of a carbocation that would rearrange so the third product is wrong and it would be CH3CHCHCOOH.
I would suggest the following syntheses.
CH2OHCH2CH2COOH :rarrow:conc H2SO4 CH3CHCHCOOH :rarrow:MCPBACH3C2H2OCOOH :rarrow:BF3,NH3CH3CHOHCHNH2COOH
the second step involves the formation of an epoxy and the third is the epoxy ring opening with NH3 and a Lewis acid.

Offline wildfyr

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Re: Organic chemistry reactions from 4-hydroxybutanoic acid to threonine
« Reply #2 on: August 03, 2019, 08:17:22 AM »
Guys, use a chemical drawing system. If you are in school chemdraw is probably available, otherwise there are some free ones on the internet

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