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Aldehydes and ketones

<b>Explain how the products of the reactions between propanal and and NaB4 and propanal look with KCN/dilute H2SO4 cannot be distinguished between using plan polarised light</b>

Propanal with NaB4 - propan-1-ol

propanal with HCN/ dilute H2SO4 - propanenitrile

Does the answer to the question involve the fact that CN- nucleophile has an equal chance of attacking above and below the planar carbonyl bond.
(edited 6 years ago)
Reply 1
I think the spell checker might have mangled your Q.

Trying to read between the mess, reduction won't lead to chiral carbons. If you reduce an aldehyde, you'll make a primary alcohol which won't be chiral. Reduction of a ketone will lead to a secondary alcohol, which could be chiral, except in this case, there are two CH3 groups attached to the central C, so no stereoisomerism.

The hydroxynitrile, on the other hand, is chiral and it is indeed a case that the CN- can attack from either side.
Reply 2
Original post by Pigster
I think the spell checker might have mangled your Q.

Trying to read between the mess, reduction won't lead to chiral carbons. If you reduce an aldehyde, you'll make a primary alcohol which won't be chiral. Reduction of a ketone will lead to a secondary alcohol, which could be chiral, except in this case, there are two CH3 groups attached to the central C, so no stereoisomerism.

The hydroxynitrile, on the other hand, is chiral and it is indeed a case that the CN- can attack from either side.


Just fixed the spell checker issue now. Idk why I put ketones in the title both are related to aldehydes.

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