For each of the three crossed aldol reactions described in Problem 47, indicate which, if any, of the multiple possible products should predominate in the reaction mixture and explain why.

Data From Problem 47

Write all possible products of the base-catalyzed crossed aldol reactions between each pair of reaction partners given below. (Multiple products are possible in every case; be sure to include thermo-dynamically unfavorable as well as favorable ones.) 

(a) Butanal and acetaldehyde 

(b) 2,2-Dimethylpropanal and acetophenone 

(c) Benzaldehyde and 2-butanone