(R)-2-Methylcyclohexanone was placed in a flask containing 0.9 equivalents of LDA at -78°C. The flask was then warmed to 0°C and benzaldehyde was added to the solution. How many stereoisomeric products can be isolated from the mixture? A. 4 Correct Answer B. 3 Your Answer O C. 2 O D. 1 ✓ Question Explanation A. (R)-2-Methylcyclohexanone contains a single stereocenter. When t ketone is added to LDA, the less substituted carbon is deprotonated generating the kinetic enolate. This does NOT affect the stereocenter more substituted carbon. However, there is more ketone than base, an result not all of the ketone is deprotonated. Thus when the solution is warmed to 0°C, the kinetic enolate tautomerizes to the more stable thermodynamic enolate. This racemizes the stereocenter of the enolate adds to the benzaldehyde. Since both the top and bottom of the syste the enolate can react with either the top or bottom of the system of th benzaldehyde, the products formed will each have two stereocenters, all possible combinations of configurations will be produced. Therefo four possible stereoisomeric products can be isolated. Concepts tested

(R)-2-Methylcyclohexanone was placed in a flask containing 0.9 equivalents of LDA at -78°C. The flask was then warmed to 0°C and benzaldehyde was added to the solution. How many stereoisomeric products can be isolated from the mixture? A. 4 Correct Answer B. 3 Your Answer O C. 2 O D. 1 ✓ Question Explanation A. (R)-2-Methylcyclohexanone contains a single stereocenter. When t ketone is added to LDA, the less substituted carbon is deprotonated generating the kinetic enolate. This does NOT affect the stereocenter more substituted carbon. However, there is more ketone than base, an result not all of the ketone is deprotonated. Thus when the solution is warmed to 0°C, the kinetic enolate tautomerizes to the more stable thermodynamic enolate. This racemizes the stereocenter of the enolate adds to the benzaldehyde. Since both the top and bottom of the syste the enolate can react with either the top or bottom of the system of th benzaldehyde, the products formed will each have two stereocenters, all possible combinations of configurations will be produced. Therefo four possible stereoisomeric products can be isolated. Concepts tested

Chemistry for Today: General, Organic, and Biochemistry

9th Edition

ISBN:9781305960060

Author:Spencer L. Seager, Michael R. Slabaugh, Maren S. Hansen

Publisher:Spencer L. Seager, Michael R. Slabaugh, Maren S. Hansen

Chapter14: Aldehydes And Ketones

Section: Chapter Questions

Problem 14.36E: Not all aldehyde give a positve Bendicts test. Which of the follwing aldehydes do? a. d. b. e. c.

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