Ethers- Williamson Ether Synthesis
Ethers- Williamson Ether Synthesis Chem 2325
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This 8 page Class Notes was uploaded by Faiqa Rahman on Monday February 8, 2016. The Class Notes belongs to Chem 2325 at University of Texas at Dallas taught by Dr. Christina Thompson in Spring 2016. Since its upload, it has received 31 views. For similar materials see Organic Chemistry in Chemistry at University of Texas at Dallas.
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Date Created: 02/08/16
Chapter 14 –Ethers-‐ Williamson Ether Synthesis • Involves an SN attack of alkoxide 2on unhindered primary halide or tosylate • Alkoxide is commonly made by add Na, K or NAH to the alcohol − − R O R’ X R O R’ X Phenyl Ethers: • Phenoxide ions are easily produced because the alcohol proton is acidic • Phenyl halides and tosylates cannot be used in this synthesis method. OH O − Base Why can’t you do a Williamson Ether? Remember you can’t backside attack a ring! Because Williamson does SN backside attack, you can’t have 2 ring as a leaving group. So when you have an ether like this: O Then you must use this as a leaving group O − X Or If using phenoxide, then it must be the one to do the attack Alkoxymercuration/Demurcuration: **Alcohol Use Mercuric acetate with Alcohol attaches to the more Hg (OAc) 2 substituted R-‐OH Carbon** ROH Hg O-‐R O-‐R NaBH 4 Hg H Cleavage by HI/HBr: Step 1: Protonation of Oxygen: Step 2: Halide attacks carbon and displaces alcohol Step 3: Alcohol further reacts with acid to make another mole of alkyl halides. R groups become alkyl halides. Remember!!: It doesn’t work with phenols!! H You can’t O + backside attack rings!!! Br − However…. O OH HBr Br + Examples: − NaH − OH O Br O O − I KOMe O OAc OAc Hg(OAc) 2 Hg OH Hg(OAc) 2 O O NaBH 4 Try this! ? ? O First you have to determine which of these would be the best nucleophile and electrophile. X OH + OR HO X **Leaving group + is not on phenol** Answer: X HO O NaOH + Next Problem: Cl HBr ? O Answer: Cl Cl HBr O + Br O H Cl Cl Cl HBr + O O H 2 Br Cl Br Last Problem: ? OH O Answer: H SO 2 4 OH Hg(OAc) 2 MeOH NaBH 4 OCH 3 Autoxidation: • Ether slowly oxidizes to hydroperoxides and diakyl peroxides. • Both are highly explosive!!
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