Lecture 6 AB - The Carboxylic Acid Family: Part III O R X...

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The Carboxylic Acid Family: Part III R X O R O O O Acid chloride R C N R O R O R R N O H R R O O H Acid anhydride Ester Nitrile Amide Lecture 5A
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Top 10 reactions of Carboxylic Acid and Derivatives 1. Hydro lysis (a-e) 2. Synthesis of acid chlorides 3. Synthesis of acid anhydrides 6. Grignard Reaction 7. Reduction 8. Alkylation of β -keto esters or diesters . Claisen Reaction 2 4. Synthesis of esters (a-c) 5. Synthesis of Amides (a,b). 9. (like Aldol) 10. Decarboxylation of β -keto acids
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“Simplified” view of hydrolysis vrs synthesis R Cl O R O R O O O O H 2 O H 2 O H 2 + + + Rxn # 1a-d Rxns 3 R O R N O R' R OH O O H 2 O H 2 O H 2 O H 2 O H 2 R O O + - - - - Cl R H H H O H R N H 2 R' # 2-5
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RECALL Acid Chlorides, Acid anhydrides, Nitriles are typically synthetic intermediates. Amides and Esters are the high value synthetic 4 targets. Carboxylic acids are produced by hydrolysis of other members of the carboxylic acid family and are the thermodynamic resting place. • Often used as starting materials.
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2. Synthesis of Acid Chlorides • SOCl 2 = thionyl chloride R OH O SOCl 2 R Cl O SO 2 Cl H + + 5 • Why can’t we just mix HCl and an acid as we show in our simplified Scheme on previous Slide ? Lets see what happens if we try this:
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Mechanism of acid chloride formation R OH O Cl S Cl O .. R O S Cl O O -H+ - Cl - Cl 6 R Cl O S O O + Mechanism is similar to reaction of alcohols with thionyl chloride + Cl -
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Aside: Another method for acid chloride formation (II) R OH O Cl O Cl O .. R O O O O Cl Cl H + 7 R Cl O C C + O O + O .. Very Interesting Mechanism!! Oxalyl chloride ? + HCl
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“Simplified” view of hydrolysis vrs synthesis R Cl O R O R O O O O H 2 O H 2 O H 2 + + + Rxn # 1a-d Rxns 8 R O R N O R' R OH O O H 2 O H 2 O H 2 O H 2 O H 2 R O O + - - - - Cl R H H H O H R N H 2 R' # 2-5
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3. Synthesis of Acid Anhydrides R Cl O R O O O R R O O + NaCl Na+ 9
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“Simplified” view of hydrolysis vrs synthesis R Cl O R O R O O O O H 2 O H 2 O H 2 + + + Rxn # 1a-d Rxns 10 R O R N O R' R OH O O H 2 O H 2 O H 2 O H 2 O H 2 R O O + - - - - Cl R H H H O H R N H 2 R' # 2-5
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4. Synthesis of esters a) Fischer esterification (reversible!) R O R O R'OH H + O H 2 + + 11 OH OR' excess This method is used when R is valuable and R’OH is cheap and can be used as a solvent eg MeOH McMurry 7e 21.3 p. 796
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Fischer esterification is reverse of hydrolysis (PATLD) R OH O R O OR' R'OH H + O H 2 + + - H + + H + 12 Mechanism: McMurry 7e 21.3 p. 796 Need to know for Test 2!
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Preparation of Fatty acid Methyl Esters: Analyzing Cell Membrane Composition 13
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4b Synthesis of esters via acid chlorides R Cl O R'OH N R OR' O N + + H Cl- + 14 This method is used when R’OH is valuable , eg steroid ; pyridine is a non-nucleophilic base (proton scavenger).
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4c Synthesis of esters via acid anhydrides R O R O O R OR' O R O O R'OH H + 15 Mechanism is similar to that for ester synthesis using acid chlorides
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A cetyl Spir saure) OH O OH OH O O O O O O OH O H+ + 16 Why don’t we see this mixed anhydride product? O
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Lecture 6 AB - The Carboxylic Acid Family: Part III O R X...

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