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Author: Subject: Haloalkane synthesis help
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[*] posted on 16-9-2010 at 19:22


Quote:
Perhaps you meant PhCH2C(=O)CH2CH3 would result?


Nope.

Quote:
Or anhydrous NH3 can react/dehydrate with esters, replacing the linking oxgen. --C(=O)NHCH2--


RCOOR' + NH3 ----> RCONH2 + R'OH




I weep at the sight of flaming acetic anhydride.
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Anders2
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[*] posted on 16-9-2010 at 19:25


Okay then,
What about acetic acid, condense with Analine to form the imine, CH3C(=NPh)NH(Ph), then react with Br2 using an oil soluble acid to form the C=C double bonded tautomer, then reduce the sensitive N--Br back to NH, now use this:
BrCH2C(=NPh)NHPh to couple with PhMg ?

Those protective analines can be gotten rid off after

about that last one,
RCONH2 HOCH2R
you are probably correct, but that should not matter,
the RCONH2 can still be hydrolyze to the carboxyl salt with a base.

[Edited on 17-9-2010 by Anders2]
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DDTea
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[*] posted on 16-9-2010 at 19:40


Quote: Originally posted by Anders2  
Okay then,
What about acetic acid, condense with Analine to form the imine, CH3C(=NPh)NH(Ph), then react with Br2 using an oil soluble acid to form the C=C double bonded tautomer, then reduce the sensitive N--Br back to NH, now use this:
BrCH2C(=NPh)NHPh to couple with PhMg ?

Those protective analines can be gotten rid off after

about that last one,
RCONH2 HOCH2R
you are probably correct, but that should not matter,
the RCONH2 can still be hydrolyze to the carboxyl salt with a base.

[Edited on 17-9-2010 by Anders2]


Look at the mechanism for formation of a Schiff base. That lone pair is required to form the carbinolamine. When you've got an acid (acetic acid here) and a base (aniline here), the first--and fastest--reaction is going to be a proton transfer, which means the Nitrogen's lone pair is no longer free to react with the carbonyl. As such, this only really works with aldehydes and ketones.

Amide formation from carboxylic acids and amines also gives low yields--the equilibrium is pretty unfavorable here.

In Organic Chem, it's as important to know when something *won't* happen as it is to know when something *will* happen.

[Edited on 9-17-10 by DDTea]




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[*] posted on 17-9-2010 at 13:51


I obviously agree with everything above, I just thought the process would go without saying, so I did not elaborate.

Obviously RCOOH would have to be made to first condense with analine. RCONH(Ph) ,analogous to condensation of amino acids. (or SCl2 could be used to form RCOCl which could then condense with an amine)

Then the condensation to the imine (with another PhNH2)would would be carried out under strongly basic conditions.

RCONH(Ph) + H2N(Ph) ==KOH==> RC(=NPh)NH(Ph) + H2O
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