Felkin-Anh model - used to predict/explain the asymmetry induced upon nucleophilic attack at a C=O with an a-asymmetric centerbearing substituents of differing size.MSML = largeM= mediumS = smallMSOH1) Nu:2) H+=0NuR1) Nu:-2) H+NuOHRFelkin-Anh model - makes three assumptions:1) the most reactive conformers are 1 & 2, where the large group (L) is perpendicular to the C=O plane2) nuc. attack occurs at the C=O face opposite the large group (L)3) most reactive of the two conformers has the SMALLEST group in the trajectory of the Nu:,a-chiral center makes C=O faces diastereotopic; i.e., nucleophilic attack leads to diastereomers A & B (in unequal amountssince the chiral center induces asymmetry in the newly forming chiral center)IINu:M$Rrotate180°S1) Nu:2) H+Nu1)2)OHMØSRNu:H+NuMBürgi-Dunitz trajectory: nucleophiles approach C=O at an oblique angle (~100° w/respect to C=O axis)OHB-NuOH*=*2...nucleophile encounters more steric repulsion in conformer 2; thus, B is the major productQ: Why not simply ask which is the most stable product?A: Because product stability is only important in reversible (equil.) rxns - the hydride reduction is essentially irreversible (non-equil. rxn).Thus, product ratio is established by fastest rxn pathway (smallest AG‡ for the SLOW step — kinetic control)& NOT by the most stable product (smallest AG- thermodynamic control).NuRNu4OH5 FELKIN-ANH MODEL PREDICTIONS14) MPV reduction of BENZOINConsider the sizes of the substituents on the a-carbon of benzoin to be as follows: H = small; OH = medium; Ph = large.In the space below, and in a manner like that shown in the lab lecture notes, analyze the hydride reduction of benzoin using the Felkin-Anhmodel and clearly indicate the major diol diastereomer predicted to form.15) MPV reduction of BENZOIN PIVALATEConsider the sizes of the substituents on the a-carbon of benzoin pivalate to be as follows: H = small; Ph = medium; -O₂C-C(CH3)3 = large.In the space below, and in a manner like that shown in the lab lecture notes, analyze the hydride reduction of benzoin pivalate using theFelkin-Anh model and clearly indicate the major diastereomer of product predicted to form.

The MPV reduction of benzoin is given as follows: According to the given problem, let's mark the…

FELKIN-ANH MODEL PREDICTIONS 14) MPV reduction of BENZOIN Consider the sizes of the substituents on the a-carbon of benzoin to be as follows: H = small; OH = medium; Ph = large. In the space below, and in a manner like that shown in the lab lecture notes, analyze the hydride reduction of benzoin using the Felkin-Anh model and clearly indicate the major diol diastereomer predicted to form.

FELKIN-ANH MODEL PREDICTIONS 14) MPV reduction of BENZOIN Consider the sizes of the substituents on the a-carbon of benzoin to be as follows: H = small; OH = medium; Ph = large. In the space below, and in a manner like that shown in the lab lecture notes, analyze the hydride reduction of benzoin using the Felkin-Anh model and clearly indicate the major diol diastereomer predicted to form.

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter20: Dienes, Conjugated Systems, And Pericyclic Reactions

Section: Chapter Questions

Problem 20.25P

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