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Carboxylic acid reactions
Why doesnt any carboxylic acid react with 2,4 DNP?
Cz it reacts with the C=O bond in aldehydes and ketones, but not in somthing like ethanoic acid? I think its somthin to do with the OH electronegativity but not really sure...
Ay help wud be great, thx
Cz it reacts with the C=O bond in aldehydes and ketones, but not in somthing like ethanoic acid? I think its somthin to do with the OH electronegativity but not really sure...
Ay help wud be great, thx
yeah the OH will inevitable change the properties of the acid and so i think it has something to do with that , not sure of the exact details;
I think its to do with the lone pairs on the oxygen atom. It causes more delocalisation in the molecule. This means that it it more stable and more resistant to addition reactions associated with the Brady's test
Loz17
I think its to do with the lone pairs on the oxygen atom. It causes more delocalisation in the molecule. This means that it it more stable and more resistant to addition reactions associated with the Brady's test
This is correct. You have two resonance forms in a carboxylic acid and if you add something onto the carbonyl carbon, you would lose this resonance stability.
argh, my bad, didnt think made the other thread, ignore this....
... or enjoy the smilies
... or enjoy the smilies
Mali Singh
Why dont Carboxylic acids react with 2,4-DNP?
Because its the C=O bond of the aldehydes and ketones which react with it, so why cant somthing like ethanoic acid? I reckon its summin to do with the electronegativity of the OH-, but not really sure...
Any help would be great, thx
Because its the C=O bond of the aldehydes and ketones which react with it, so why cant somthing like ethanoic acid? I reckon its summin to do with the electronegativity of the OH-, but not really sure...
Any help would be great, thx
It has to do with electrophilicity of the central carbon.
In aldehyde and ketones, the C is attached to O which is highly electronegative and pulls electron density away, promoting attack by nucleophiles(seeking "positive" charge)
For carboxylic acid, the lone pair on each of the oxygen can delocalize via their pi framework, meaning that the central C is less electrophilic(less "positive") therefore more resistant to attack by nucleophile(which is DNP in this case)
Kyri
This is correct. You have two resonance forms in a carboxylic acid and if you add something onto the carbonyl carbon, you would lose this resonance stability.
Thats what I was trying to say, further explained it better. Thanks
"Dinitrophenylhydrazine does not react with other carbonyl-containing functional groups such as carboxylic acids, amides, and esters. For carboxylic acids, amides and esters, there is resonance associated stability as a lone-pair of electrons interacts with the p-orbital of the carbonyl carbon resulting in increased delocalisation in the molecule. This stability would be lost by addition of a reagent to the carbonyl group. Hence, these compounds are more resistant to addition reactions."
Basically lone pairs keep it stable, removing these to add 2,4-DNP is too difficult
Basically lone pairs keep it stable, removing these to add 2,4-DNP is too difficult
ahh that makes sense thanks v much, +ve rep coming ur way 
Haz Shah
probably something to do with the electronegativity of the C=O in a Carboxyl Group.. but don't get me wrong, but I don't think we have to know this for Chemistry A2..
think we mite (for edexcel at least), the OH- or Cl- contribute to a load of different properties between aldehydes/ketones and othrs like bpt and mpt and reactions especially
Nyway thanks v. much evry1 who's posted
Mali Singh
think we mite (for edexcel at least), the OH- or Cl- contribute to a load of different properties between aldehydes/ketones and othrs like bpt and mpt and reactions especially
Nyway thanks v. much evry1 who's posted
Nyway thanks v. much evry1 who's posted
Uhm, well the most common answer for A2 Chemistry is to do with their Stability to resist stuff.. so just go with the delocalisation of the C=O in a Carboxyl Group having a Lower Electron Density, hense why its more stable, and more resistant to Bradley's reagent (2,4 DNP)
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