[ysk1]

Hi guys,

I have an exam tomorrow. I'd appreciate it if you could answer the two questions below:

1. You can only turn a carboxylic acid derivative into its less reactive
derivative (eg. from acyl halide to ester but never vice versa). But how come you can add a proton and water to amide and turn it into a carboxylic acid, even though
amide is less reactive than carboxylic acid?

2. What's the real point of using NaBH(OAc)3 instead of NaBH3 in turning an
iminium ion into an amine? It's said that its purpose is to make a less reactive
hydride, but can't you just use NaBH3 instead?

Thanks.

[agrobert]

1. Please give your definition of carboxylic acid reactivity.  Rank the derivatives of carboxylic acids in terms of reactivity. (Acid, acid chloride, ester, amide, anhydride, nitrile)  Also everything is reversible just not always directly in one step.

2. When you make an imine it is the result of an amine attacking an aldehyde or ketone.  If you use a strong reducing agent like NaBH₄ or LiAlH₄ you will reduce your ketone or aldehyde as well.  Make sense?  Ask questions.

[venkatjohnny]

Hi,
it's nice to see your questions, infact your questions are good. I hope i can answer your second question rather than the first!!! NaBH(OAc)3 is a selective reagent for the conversion of Imine to an amine because of its less reactive hydride ( due to the presence of OAc group). But NaBH4 is a strong reducing agent (not strong as LiAlH4) which may reduce the other functional groups present in your molecule. This is what i'm thinking from my side, All the best for your exams..
hmmm i think carboxylic acids are more stable than their respective derivatives bcz they are not only resonance stabilised but also  have intermolecular H-bonding( always exists as dimers). Due to this driving force carboxylic acid derivatives converts to acids even though they are less reactive than acids... Have a nice time n wish u the very best...


Hi guys,

I have an exam tomorrow. I'd appreciate it if you could answer the two questions below:

1. You can only turn a carboxylic acid derivative into its less reactive
derivative (eg. from acyl halide to ester but never vice versa). But how come you can add a proton and water to amide and turn it into a carboxylic acid, even though
amide is less reactive than carboxylic acid?

2. What's the real point of using NaBH(OAc)3 instead of NaBH3 in turning an
iminium ion into an amine? It's said that its purpose is to make a less reactive
hydride, but can't you just use NaBH3 instead?

Thanks.