Chapter 11 Study Guide

Chapter 11 Study Guide - 1 Chapter 11 Alcohols, Ethers and...

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Chapter 11 Alcohols, Ethers and Phenols Alcohols—structure, nomenclature and properties as before Phenol—benzene with OH attached Ether—ROR, where R = alkyl group Simple ethers are named using the alkyl group attachements. Butyl pentyl ether above. ethyl methyl ether tert-butyl ethyl ether diethyl ether In more complex molecules, ethers are named as alkyloxy. Examples methoxy, ethoxy… 6 -tert-butoxy-5-ethoxy-2-methoxy-4-methyl-3-octen-1-ol O H O O O O O O OH O 1
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Cyclic ethers—3-sided—oxirane, 4-sided—oxetane, 5-sided—THF, 6-sided—1,4-dioxane Physical properties of ether— No hydrogen bonding possible so ethers have low boiling points similar to hydrocarbons However because of Oxygen ethers are good solvents can dissolve organics and ionics. Some common examples- Methanol—wood alcohol, originally prepared by distillation of wood toxic, small quantities can cause blindness, large quantities—death Ethanol—drinking alcohol, made through fermentation of sugars sugars can come from many sources mostly grain, hence, grain alcohol Fermentation can only generate maximum 12-15%v/v of ethanol due to high solubility of water. To get higher percentages water must be distilled away. Hence Jack Daniels Distillaries…Proof = 2 x’s the %. 100 proof = 50%. Even with distillation highest percentage possible is 95%. The last 5% of water can not be eliminated because it forms an azeotrope that boils at lower temperature than the ethanol itself. This is pure grain alcohol—190 proof = 95%. To remove the last 5% water impurity, benzene is added and a new azeotrope forms that boils even lower than the water/ethanol azeotrope. 200 proof = 100 % is called absolute alcohol. It is denatured by adding a toxic substance such as methanol or benzene. This is called denatured alcohol. Ethylene glycol—antifreeze Diethyl ether—flammable used as anesthetic O O O O O 2
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Synthesis of alcohols from alkenes 1) Acid-catalyzed hydration of alkenes —Chapter 8, not useful synthetically. Rearrangements make this a very non useful reaction. Markovnikov addition. 2) Oxymercuration-Demercuration— Markovnikov addition. Usually less than one hour in 90-100% yields. The mechanism for the removal of the HgOAc is not understood. CH 3 OH CH 3 CH 2 OH OH OH F 3 CC Cl H O CF 2 H HFCl F F O CF 2 H Methanol Ethanol Ethylene glycol Isofluorane Enfluorane OH H 3 O + OH 1) H 2 O/Hg(acetate) 2 THF 2) NaBH 4 /OH - Hg(OAc) 2 Hg + OAc + OAc - Hg OAc ! + Like the halohydrin intermediate H 2 O HgOAc OH 2 H 2 O 3
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3) Hydroboration-Oxidation— Anti-Markovnikov addition 1) BH 3 :THF 2) H 2 O 2 /OH - B H H H H B ! " ! + Boron adds to less substituted side. Transition state. Transition state collapses. BH 2 H syn addition Repeat twice B OO H B H B O B(OR) 3 R = Hydrolyze 3 3 OH 4
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Reaction of Alcohols The OH of the alcohol is basic and can act as a nucleophile. It is a very bad leaving group. Protonation of the alcohol makes the OH a good leaving group. Water has a pKa of 15.7. Most alcohols have higher pKa than water(the exception being methanol). This is due to the steric hindrance created by the alkyl groups.
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This note was uploaded on 04/10/2010 for the course CHE 326 taught by Professor Chisholm during the Spring '08 term at Syracuse.

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Chapter 11 Study Guide - 1 Chapter 11 Alcohols, Ethers and...

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