Sciencemadness Discussion Board

How synthesized a caboxylicacid ?

Madandcrazy - 14-5-2006 at 08:22

I searching in the forums, but i could not found some entry to this theme.
I think it is interested when a sensitive material should converted to a carboxylic acid and can not easy oxidized.
Example is maybe when benzoic acid should prepared from
benzyl alcohol or benzaldehyde and CO2 gas.
But what should i do when for instance sensitive chemicals should synthesized ?
When for instance the glycin should prepared, can it synthesized by formic acid and chloroamin. It it shourely not a easy question.
Maybe the way chloromethane is oxidized with H2SO4 and CO2 to chloromethanecarboxylic acid and this is by any method converted to the glycin.

turd - 14-5-2006 at 09:14

Apart from oxidation, most carboxylic acid syntheses play on the themes of:

*) Hydrolysis of nitriles
R-Cl + CN- --(-Cl-)--> R-CN --(H+/H2O)--> R-COOH
R-CHO + CN- ----> R-CHOH-CN --(H+/H2O)--> R-CHOH-COOH
R-CHO + CN- + NH3 ----> R-CH(NH2)-CN --(H+/H2O)--> R-CH(NH2)-COOH

*) Grignards with CO2
R-Cl + Mg ----> R-MgCl --(+CO2)--> R-COO-MgCl --(H+/H2O)--> R-COOH

*) Saponification of esters
R-Cl + NaCH(COOEt)2 --(-NaCl)--> R-CH(COOEt)2 --(H+/H2O)--> R-CH(COOH)2 --(-CO2)--> R-CH2-COOH
CH2(COOEt)2 --(Br2)--> Br-CH(COOEt)2 --(NH3)--> NH2-CH(COOEt)2 --(H+/H2O)--> NH2-CH(COOH)2 --(-CO2)--> NH2-CH2-COOH

And probably lots more.

For amino-acids you could also brominate an acid and aminate it:
R-COOH --(PBr3)--> RBr-COOH --(NH3)--> R(NH2)-COOH

With the exception of the Grignard, these methods should work for glycine.

Madandcrazy - 16-5-2006 at 07:18

Thanks for the reply.

i mean when for instance a carboxylic acid is brominated,
where the bromine is attacking the acid.
CH3-CH2-COOH and Br2 should give at least
CHBr-CBr-COOH or
CHBr2-CBr-COOH. ;)

Maybe the this syntheses is failed and is ending with
CHBr2-CBr-COOBr.

[Edited on 16-5-2006 by Madandcrazy]

turd - 17-5-2006 at 08:58

Quote:

i mean when for instance a carboxylic acid is brominated,
where the bromine is attacking the acid.
CH3-CH2-COOH and Br2 should give at least
CHBr-CBr-COOH or
CHBr2-CBr-COOH. ;)

No, look up the Hell-Volhard-Zelinsky reaction. I've never tried it, so I can't comment on its reliability. Of course you shouldn't have any double bonds or similar in your compound.

Madandcrazy - 19-5-2006 at 07:41

Why not any double bindings ?

Maybe by the carboxylic acid the -CBr=O group ;) can be synthesized when it treated
strong enough.

[Edited on 19-5-2006 by Madandcrazy]