6_alcohols_and_ethers_post

6_alcohols_and_ethers_post - Alcohols Order the following...

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Sec. 6: Alcohols, Ethers 1 Alcohols Order the following compounds from most to least acidic? A) 1 > 2 > 3 B) 3 > 2 > 1 C) 2 > 1 > 3 D) 3 > 1 > 2 E) 1 > 3 > 2 Which of the following equilibriums would not be shifted to the right? OH A) CH 3 O O CH 3 OH B) OH 2 CH 3 O C) + + + O CH 3 OH OH CH 3 O + OH CH 3 OH + + C OH OH 2 1 2 3 HO
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Sec. 6: Alcohols, Ethers 2 Alcohols may be weakly basic as well as being acidic. Molecules that can be both acidic and basic are called amphoteric . RO H 2 H Alkoxonium ion Alcohol Alkoxide ion Strong Acid Strong Base Weak acid and base strong acid mild base strong base mild acid Very strong acids are required to protonate alcohols.
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Sec. 6: Alcohols, Ethers 3 Preparation of Alcohols 90 % 10 % A) S N 1 B) S N 2
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Sec. 6: Alcohols, Ethers 4 Oxidation States of Carbon A reaction of an organic molecule usually corresponds to increasing its hydrogen content or decreasing its oxygen content. RCH 3 [O] [H] RCH 2 OH [O] [H] RC O H [O] [H] O OH Lowest Oxidation State Highest Oxidation State H R OH RC R O [O] [H] Oxidation broad definition a reaction that increases its content of any element more electronegative than carbon CH 3 [O] [H] CH 2 Cl How to figure out the oxidation state of a carbon atom a bond to hydrogen or anything less electronegative than carbon is electron donating -1 a bond to nitrogen, oxygen or anything more electronegative than carbon is electron withdrawing +1 a bond to a carbon 0 C H H H H CO O C H H H C H OH H OS = oxidation state OS = OS = OS = OS =
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Sec. 6: Alcohols, Ethers 5 Oxidation States of Carbon C C H H H H H 2 /Pd C H H H C H H H LEO goes GER L oss of E lectrons O xidation, G ain of E lectrons R eduction C H H H C H OH H KMnO 4 C H H H C O OH Reduction Oxidation Alcohols can form by hydride reduction of the carbonyl group The carbonyl functional group is polarized due to the high electronegativity of the carbonyl oxygen atom: OS = OS = OS = OS =
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Sec. 6: Alcohols, Ethers 6 Alcohols by Reduction of Carbonyl Compounds with LiAlH 4 and NaBH 4 The carbonyl group is susceptible to nucleophilic attack. Nucleophile (base) Electrophile (acid) These reductions are achieved by the addition of a H¯ ion (nucleophile) to the electropositive carbon and a proton to the electronegative oxygen The carbonyl carbon can be attacked by a nucleophilic hydride ion, H¯, furnished by a hydride reagent. Sodium borohydride, NaBH 4 , and lithium aluminum hydride, LiAlH 4 , are commonly used for hydride reductions because their solubilities are higher in common organic solvents than LiH and NaH.
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Sec. 6: Alcohols, Ethers 7 Mechanism with LiAlH 4 and NaBH 4 C O R R Na H 3 B- H + C O R R H Na H 2 O CH 3 CH 2 OH solvent + BH 3 C O R R H BH 3 C O H R R H CH 3 CH 2 O H + CH 3 CH 2 O + BH 3 This will react three more times C O R R 4 ( CH 3 CH 2 O ) 4 B + C OH R R H NaB(OH) 3 CH 3 CH 2 OH + + CH 3 CH 2 O H C O H R R H
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Sec. 6: Alcohols, Ethers 8 C O R R Li H 3 Al- H + C OAlH 3 Li R R H + C O R R 3 C O R R H Al O O O C R H R C C R R RR H H a tetra-alkyl aluminate H 3 O + C OH R R H The reactivity of LiAlH 4 is much greater than that of NaBH 4 and is less selective in its reactions.
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This note was uploaded on 07/10/2010 for the course CHEM 266 taught by Professor Pols during the Spring '07 term at Waterloo.

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6_alcohols_and_ethers_post - Alcohols Order the following...

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