chem lab 8 - Hoang 1 Phuong Hoang Chem 3105 541 10/29/08...

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Hoang 1 Phuong Hoang Chem 3105 – 541 10/29/08 Experiment 8: The Williamson Ether Synthesis: An S N 2 Reaction I. Purpose: The purpose of this experiment is to prepare an ether using the Williamson ether synthesis. II. Background: The reaction of the experiment: NaOH H 3 C- C 6 H 5 - OH + CH 3 CH 2 CH 2 I H 3 C- C 6 H 5 - OCH 3 CH 2 CH 2 + NaI p-cresol (C 4 H 9 )N + Br - propyl p-tolyl ether The reaction follows the S N 2 pathway with the backside nucleophilic attack of the phenoxide anion on the alkylhalide. H 3 C- C 6 H 5 - OH + NaOH H 3 C- C 6 H 5 - O - Na + + H 2 O δ - δ - H 3 C- C 6 H 5 - O - Na + + CH 3 CH 2 CH 2 I [H 3 C- C 6 H 5 - O--- CH 2 ---I] | CH 2 CH 3 (transition state) H 3 C- C 6 H 5 - OCH 2 CH 2 CH 3 + Na + I - In this reaction, (C 4 H 9 )N + Br - acts as the phase-transfer catalyst. It carries the phenoxide ion, as an ion-pair, from the aqueous phase into the organic phase, where the S N 2 reaction occurs. The ether product and the corresponding halide salt of the catalyst are produces in this reaction. The
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This note was uploaded on 01/28/2009 for the course CHEM 3105 taught by Professor Zhang during the Spring '09 term at Texas Tech.

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chem lab 8 - Hoang 1 Phuong Hoang Chem 3105 541 10/29/08...

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