Write equations and give the mechanism for the reaction of butanone with: 1) NaBH4 and 2) HCN

The first thing we need to do in this type of organic chemical reaction, is identify our electrophiles and nucleophiles. We know that due to the electronegativity of the oxygen atom in carbonyl compounds that the carbon atom is electrophilic so in both cases here the carbon atom of the carbonyl compound of butanone is going to be our electrophile. In case 1) we know that B-H bonds are polarised in a way that can produce hydride ions (a nucleophile) and in case 2) we know that cyanide is a good nucleophile also. Now having Identified out electrophiles and nucleophiles in each case we can start to draw the mechanism of our reaction:

(need white board)

Addition of our identified nucleophiles into the the electrophilic centre of the carbonyl pushes electrons from the C=O double bond onto the oxygen atom, forming a tetrahedral intermediate. Protonation of the anionic oxygen will then give our products 1) 2-butanol and 2) 2-hydroxy-2-nitrilebutane. This problem is a great example of using our understanding of atomic structure and the periodic table to identify reactive species in an organic reaction!