Solvent and temperature effect in aldol condensation between the lithium enolate of tert-butyl acetate and 2-phenyl propanal: enthalpy and entropy contribution
✍ Scribed by Gianfranco Cainelli; Paola Galletti; Daria Giacomini; Paolo Orioli
- Book ID
- 104231376
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- French
- Weight
- 65 KB
- Volume
- 42
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
An analysis of nucleophilic addition of the lithium enolate of tert-butyl acetate and 2-phenyl propanal in two different solvents, such as THF and n-hexane, revealed the great importance of solvent effect in determining the stereoselectivity. In particular, temperature-dependent measurements of diastereomeric ratio allow the evaluation of diastereoselectivity in terms of differential enthalpy and entropy of activation for this reaction. Either in THF or n-hexane we obtained a predominance of the anti isomer in all temperature ranges, but in THF the diastereoselection is controlled by the differential activation enthalpy, whereas in n-hexane it is the sole differential activation entropy that accounts for the anti predominance.