Question

Ethane nitrile to ethanol: convert??

Answer 1

You can do an acid-catalyzed hydrolysis with heat, followed by a very strong hydride donor.

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Nitriles are quite hard to hydrolyze, and you'll need heat to get it to a carboxylic acid. Then, reduction to the alcohol gives ethanol...

The first mechanism is doable in `8 - 10` minutes. You would not have to know the mechanism for the reduction, as it is fairly complicated.

1. Protonate the nitrogen.
2. Water attacks the electrophilic carbon. Heat facilitates it because it's not as electrophilic as in a ketone.
3. Proton transfer to the nitrogen.
4. Tetrahedral collapse to form the protonated amide intermediate.
5. A second equivalent of a water molecule attacks the electrophilic carbon.
6. Proton transfer to the nitrogen again.
7. Tetrahedral collapse to let the ammonia leave, forming the protonated carboxylic acid product of the hydrolysis.
8. Ammonia equilibrates with the protonated carboxylic acid to leave ammonium as the protonated product (`"K"_a` is over `10^8` bigger than that of ammonium).

Make sure you remove the ammonium so that you don't form ammonia AND `"H"_2` gas in the reduction process next.

This hydride donor, lithium aluminum hydride, is what is sufficient to reduce acetic acid down to ethanol. Carboxylic acids will NOT react with `"NaBH"_4`, but they will react with `"LiAlH"_4`.