[dumakey1212]

I've been given this problem and am told to write out the mechanism.
http://imagizer.imageshack.us/v2/800x600q90/21/1ik4.png

I'm familiar with substitutions and additions, and I know when I see NaCN that it's a substitution and generally H3O+ can be used in acid-catalyed hydration of alkenes, but the fact that the starting material is acetone confuses me because I have no idea how to start. Any help on this one? Thanks

[zsinger]

Simple CN- attaching to the partial positive carbon.  Nucleophilic substitution reaction (very nucleophilic, as the nucleophile has a negative charge!)  The H30+ quenches the rxn. and turns O- to Hydroxide.  Hope this helps .
          -Zack

[dumakey1212]

How does the CN- attach to the partial positive carbon when it already has four bonds to it? Is it because when the CN- attacks, it pushes one of the bonds to oxygen up on to it giving it a negative charge?

[discodermolide]

have a look at this page
http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch17/ch17-3-2-1.html

it may help you.

[zsinger]

How does the CN- attach to the partial positive carbon when it already has four bonds to it? Is it because when the CN- attacks, it pushes one of the bonds to oxygen up on to it giving it a negative charge?

Yes….this is essentially the "driving force" for the reaction.  The highly electronegative Oxygen can resonate extra electrons (from the Pi bond) up to the O atom in order to not violate the octet.  This rule is furthered, as there is surely no leaving groups on that molecule (Can't kick off H- or C-).  So there is only one thing left to do……quench the reaction with protons .
       Hope this helps your understanding.
                  -Zack

[dumakey1212]

Yeah, that sums it up perfectly. Thanks!