(a) If ethyne is treated according to the following scheme, the final product is trans-pent-2-ene, as shown: H- (c) C-H (i) NaNH, / NH (ii) CH₂Br (iii) NaNH, / NH (iv) CH3CH₂Br (v) Na/NH3 H3C H H CH₂CH3 Show the structures of the intermediates formed after each of the first four steps and identify the mechanism involved in steps (ii) and (iv). (b) If cis-pent-2-ene was wanted as the final product, how would step (v) in the sequence above must be modified? I The alkene shown in part (a) of this question could also be made by treating 2-bromopentane with base. It would be the major product out of three possible alkenes that could form. Give the structures of the two other alkenes that would form and comment on why trans-pent-2-ene is the major one that forms here.

(a) If ethyne is treated according to the following scheme, the final product is trans-pent-2-ene, as shown: H- (c) C-H (i) NaNH, / NH (ii) CH₂Br (iii) NaNH, / NH (iv) CH3CH₂Br (v) Na/NH3 H3C H H CH₂CH3 Show the structures of the intermediates formed after each of the first four steps and identify the mechanism involved in steps (ii) and (iv). (b) If cis-pent-2-ene was wanted as the final product, how would step (v) in the sequence above must be modified? I The alkene shown in part (a) of this question could also be made by treating 2-bromopentane with base. It would be the major product out of three possible alkenes that could form. Give the structures of the two other alkenes that would form and comment on why trans-pent-2-ene is the major one that forms here.

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

Chapter22: Reactions Of Benzene And Its Derivatives

Section: Chapter Questions

Problem 22.59P

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