How conjugation changes the reactivity of carbonyl groups

Click the structures and reaction arrows in sequence to view the 3D models and animations respectively

Small differences in reaction conditions, (such as temperature) can completely change the outcome of a reaction. In the first reaction shown below, you can see that it is an example of nucleophilic addition of cyanide to a ketone, giving a cyanohydrin:

Click the image to view cyanohydrin formation

However, when the temperature of the reaction is increased to 80°C, conjugate addition occurs, resulting in the addition of cyanide to the C=C double bond. Compounds with double bonds adjacent to a C=O group are known as α,β-unsaturated carbonyl compounds.

A. G. Csákÿ, G. de la Herrán and M. C. Murcia, Chem. Soc. Rev., 2010, 39, 4080.