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    Hey, I wan to ask. Does this test only give positive result with aldehyde and ketone? How about acyl chloride, amide ? I am confused that this test is just for aldehyde and ketone or carbonyl containing compounds?

    Thanks
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    (Original post by vick5821)
    Hey, I wan to ask. Does this test only give positive result with aldehyde and ketone? How about acyl chloride, amide ? I am confused that this test is just for aldehyde and ketone or carbonyl containing compounds?

    Thanks
    reactivity of carbonyl to nucleophile:

    acyl chloride > anhydride > aldehyde > ketone > carboxylic acid > ester > amide

    brady reagent involves nucleophilic lone pair on N that can react with ketone and the more reactive carbonyl above it in the series above.

    Anything below ketone(ester and amide) are more inert to nucleophiles due to more effective delocalisation of electrons from the heteroatom(ester O or amide N) into C=O anti bonding orbital.

    so in short, brady reagent would react with acyl chloride but not carb acids, esters and amide.
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    I dun understand why amide , ester and carboxylic acid cant..I dun understand the reason given..and why the reactivity is in the sequence?
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    (Original post by vick5821)
    I dun understand why amide , ester and carboxylic acid cant..I dun understand the reason given..and why the reactivity is in the sequence?
    Nucleophiles are species that are rich in electron density and by electrostatics, they would love to react with something that is positively charged(partially-ish), ie electrophiles.

    carbonyl group, by virtue of their electronegative oxygen, are sufficiently electrophilic in nature, a partial positive charge develops at the carbon centre due to this polarisation.

    how much partial positive charge developed at this carbon centre determines how strong nucleophiles would be attracted to it, and hence their reactivity towards nucleophiles.

    If you can draw resonating structures to show delocalisation of electrons from lone pairs on the singly bonded O in ester or OH in acids or N in amides, you'd realise that these are not possible in ketones, aldehydes, acid chloride. (it might be possible, but it is unfavourable)

    Oxygen is more electronegative than nitrogen, so it delocalises more reluctantly than N to stabilise partial positive charge on carbonyl, hence amide carbonyl are more resistant to nucleophiles as the partial charge on C in amides is sort of more neutralised than say in corresponding ester analogue.

    The reasoning for the other species in the sequence runs by the same argument. If you know what a brady reagent is, you'd see it is actually a nucleophile(the lone pairs on N); perhaps you should have read through my previous post more thoroughly.
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    so carboxylic more reactive than ester or vice versa? Cause my notes stated that ester is more reactive than carboxylic acids.but you said the opposite? So?
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    any link for what u have said? Cause I am not good in drawing the resonance structure thanks
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    (Original post by vick5821)
    any link for what u have said? Cause I am not good in drawing the resonance structure thanks
    ermm, would have thought since you know how to use the forum in the first place, you can definitely google what you want to find too...
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    what should I search about?
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    (Original post by vick5821)
    what should I search about?
    ermm, you search for what you want to find?
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    LOL..okay..so I should search resonance structure of carboxylic derivaties?
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    Too much "spoon-feeding" in school nowadays?
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    nope..hahaha
 
 
 
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