Keys to Success Competitive Reaction Pathways and the Intramolecular Aldol Condensation

KEYS TO SUCCESS COMPETITIVE REACTION PATHWAYS AND THE INTRAMOLECULAR ALDOL CONDENSATION 

It is possible to carry out aldol condensations between two carbonyl groups located in the same molecule. Such a reaction is called an intramolecular aldol condensation and is important in the synthesis of cyclic compounds, especially five- and six-membered rings. 

Heating a dilute solution of hexanedial with aqueous base results in the formation of the cyclic product 1-cyclopentenecarbaldehyde. Here, one end of the dialdehyde functions as the nucleophilic enolate component (after deprotonation), the other as the electrophilic carbonyl partner. After the initial aldol addition, subsequent dehydration furnishes the product. 

Why does the intramolecular aldol take place in preference to the intermolecular alternative There are two factors to consider in answering this question. The first is kinetic, that is, relating to the relative speed of the two processes The intramolecular 

Intramolecular ketone condensations Reversibility favors unstrained ring formation 

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