Mechanism of nucleophilic addition reactions :
Nucleophile attacks from the top face :
A nucleophile attacks the electrophilic carbon atom from a direction perpendicular to the plane of sp2 hybridised orbital of carbonyl carbon.The hybridisation of carbon changes from sp2 to sp3 in this process and a tetrahedral alkoxide intermediate is produced.
This intermediate captures a proton from the reaction medium to give the electrically neutral product. The net result is addition of Nu– and H+ across the carbon oxygen double bond.
