1 2008 Lectures 16 17 Ethers organosulfur - Chem...

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Chem 2203/2207 Test 2: Handed back Tuesday Nov 11 th Note: Test 2 will be reviewed in class Tuesday Nov 11 th and answers posted on http://http server.carleton.ca/~pbuist/ Today: Ethers Tuesday Nov 11 th Organosulfur compounds Remaining Topics: Dienes and Aromatics
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Ethers R O R and Organo sulfur Compounds R S H and R S R Chapter 18
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Ethers (R O R ) can be regarded as derivatives of alcohols (R O H ). Recall Williamson synthesis of ethers : R O- + R - X RO R + X- Ethers can also be synthesized by addition of R O H to alkenes: R O H + R = R R O - R-R- H This is a variation on alkene hydration: H O H + R = R H O - R-R- H
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Ethers • Important solvents • Diethyl ether: CH 3 CH 2 OCH 2 CH 3 anesthetic
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Vitamin E
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Nomenclature (1) • Diethyl ether: CH 3 CH 2 - O -CH 2 CH 3 - an example of a symmetrical ether ethylpropyl ether: CH H H H • Methylpropyl ether: CH 3 - O -CH 2 CH 2 CH 3 - an example of an unsymmetrical ether These are both dialkyl ethers: R = alkyl
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Nomenclature (2) Aromatic ethers R= Aromatic • Methylphenyl ether: (anisole) C H 3 O • Alkoxyalcohols: 2- butoxy ethanol (butyl cellosolve): CH 3 CH 2 CH 2 CH 2 - O -CH 2 CH 2 - O H
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Nomenclature (3) • R O R = Cyclic ethers (an example of a heterocycle - heteroatom is incorporated into a ring). O O O O Tetrahydrofuran (THF) Furan 2 H 2 1,4–dioxane
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Physical Properties (1) Boiling points (and melting points ) of ethers are lower than corresponding alcohol – E.g. CH 3 CH 2 O H (bp 78 ° C) vs. CH 3 - O -CH 3 (bp 5 ) -25 ° C) • Why? No Hydrogen-bonding for ethers O R H O R H . . . . . . . . O R R . . . . . . . . O R R H-Bonding No H-Bonding
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Physical Properties (2a) Solubility of acyclic ethers in water is less than that of corresponding alcohols of equal MW. – Ethers can accept H-bonds, but not donate em them O R R O H H . . . . . . . . . . . . . . . . O H H O R H O H H . . . . Vs. Note: For diethyl ether, very slight solubility in water (10%)
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Physical Properties (2b) Solubility of cyclic ethers in water is greater than that of acyclic ethers of equal MW. • Compact shape more easily accommodated by
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This note was uploaded on 07/28/2009 for the course CHEMISTRY CHEM 2203 taught by Professor Levin during the Spring '08 term at Indian Institute of Technology, Chennai.

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1 2008 Lectures 16 17 Ethers organosulfur - Chem...

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