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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: cyanzi on August 03, 2019, 04:11:19 AM

Title: Organic chemistry reactions from 4-hydroxybutanoic acid to threonine
Post by: cyanzi on August 03, 2019, 04:11:19 AM

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: ^NH_3(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?

Title: Re: Organic chemistry reactions from 4-hydroxybutanoic acid to threonine
Post by: AlirezaDehghani 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.

Title: Re: Organic chemistry reactions from 4-hydroxybutanoic acid to threonine
Post by: wildfyr 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