BASE CONDITIONS TO BE MAINTAINED:
--->This reaction is feasible in presence of bases like dil NaoH, K2CO3 , etc....
--->It is very important to remember that base conc. must be low. with increase in base conc. repeated condensation occurs and resultant products will be resins(polymers formed due to repeat condensation.)
DEHYDRATION OF PRODUCT:
--->If second α hydrogen is there on heating dehydration occurs. Resonance of new formed double bond with that carbonyl already exist is the driving force for dehydration.
FORMATION OF INTRA MOLECULAR ACETALS IN PRODUCT:
--->Generally the aldol condensation product has both alcoholic and carbonyl groups. So the products in sevaral conditions are going to be acetals.
--->So products has to isolate carefully in presence of catalysts like dil K2CO3.
REACTION
--->-I EFFECT i.e electron with drawing groups increases the reaction rate by making the carbane ion much stable, while the electron donating groups decreases reactivity.
--->Hence aldehydes are more reactive than ketones.
CROSSED ALDOL CONDENSATION BETWEEN ALDEHYDES AND KETONES:
--->If you want to condensate an aldehyde with ketone, the major product will be condesation product between aldehydes due to their reactivity.
---> So in order to get max. cross product yield add aldehyde slowly to the stirred mixture of ketone and base.
SOME EXAMPLES:
ANYONE HAVING DOUBTS REGARDING ABOVE TOPICS MAIL ; pavan@chem.iitb.ac.in
2 comments:
This page is good for information on the aldol reaction. However, for a more detailed mechanism I would suggest PharmaXChange.info | Aldol Condensation - Base Catalyzed
Post a Comment