When 2-bromo-3-phenylbutane is treated with sodium methoxide, two alkenes result (by E2

Chapter 7, Problem 7-69

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When 2-bromo-3-phenylbutane is treated with sodium methoxide, two alkenes result (by E2 elimination). The Zaitsev product predominates. (a) Draw the reaction, showing the major and minor products. (b) When one pure stereoisomer of 2-bromo-3-phenylbutane reacts, one pure stereoisomer of the major product results. For example, when (2R,3R)-2-bromo-3-phenylbutane reacts, the product is the stereoisomer with the methyl groups cis. Use your models to draw a Newman projection of the transition state to show why this stereospecificity is observed. (c) Use a Newman projection of the transition state to predict the major product of elimination of (2S,3R)-2-bromo-3- phenylbutane. (d) Predict the major product from elimination of (2S,3S)-2-bromo-3-phenylbutane. This prediction can be made without drawing any structures, by considering the results in part (b).