Chapter 21 Carboxylic Acid Derivatives (continued)

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Chapter 21Carboxylic Acid Derivatives(continued)
Organic Chemistry, 6th EditionL. G. Wade, Jr.
Jo Blackburn Richland College, Dallas, TX Dallas
County Community College District ã 2006,
Prentice Hall
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Hydrolysis of Acid Chlorides and Anhydrides

• Hydrolysis occurs quickly, even in moist air with
  no acid or base catalyst.
• Reagents must be protected from moisture.

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Acid Hydrolysis of Esters

• Reverse of Fischer esterification.
• Reaches equilibrium.
• Use a large excess of water.

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Saponification

• Base-catalyzed hydrolysis of ester.
• Saponification means soap-making.
• Soaps are made by heating NaOH with a fat
  (triester of glycerol) to produce the sodium salt
  of a fatty acid - a soap.
• One example of a soap is sodium stearate, Na
  -OOC(CH2)16CH3.
  gt

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Hydrolysis of Amides

• Prolonged heating in 6 M HCl or 40 aqueous NaOH
  is required.

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Hydrolysis of Nitriles

• Under mild conditions, nitriles hydrolyze to an
  amide.
• Heating with aqueous acid or base will hydrolyze
  a nitrile to an acid.

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Reduction to Alcohols

• Lithium aluminum hydride reduces acids, acid
  chlorides, and esters to primary alcohols.

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Reduction to Aldehydes

• Acid chlorides will react with a weaker reducing
  agent to yield an aldehyde.

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Reduction to Amines

• Lithium aluminum hydride reduces amides and
  nitriles to amines.
• Nitriles and 1? amides reduce to 1? amines.
• A 2? amide reduces to a 2? amine.
• A 3? amide reduces to a 3? amine.

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Organometallic Reagents

• Grignard reagents and organolithium reagents add
  twice to acid chlorides and esters to give
  alcohols after protonation.

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Grignard Reagentsand Nitriles

• A Grignard reagent or organolithium reagent
  attacks the cyano group to yield an imine which
  is hydrolyzed to a ketone.

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Acid Chloride Synthesis

• Use thionyl chloride, SOCl2, or oxalyl chloride,
  (COCl)2.
• Other products are gases.

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Acid Chloride Reactions (1)
acid
ester
amide
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Acid Chloride Reactions (2)
3 alcohol
ketone
1 alcohol
aldehyde
AlCl3
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Industrial Synthesis of Acetic Anhydride

• Four billion pounds/year produced.
• Use high heat (750C) and triethyl phosphate
  catalyst to produce ketene.

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Lab Synthesisof Anhydrides

• React acid chloride with carboxylic acid or
  carboxylate ion.

• Heat dicarboxylic acids to form cyclic
  anhydrides.

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Anhydride Reactions
acid
ester
amide
AlCl3
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Anhydride vs. Acid Chloride

• Acetic anhydride is cheaper, gives a better yield
  than acetyl chloride.
• Use acetic formic anhydride to produce formate
  esters and formamides.

• Use cyclic anhydrides to produce a difunctional
  molecule.

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Synthesis of Esters
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Reactions of Esters
acid
ester
amide
1 alcohol
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Lactones

• Formation favored for five- and six-membered
  rings.

• For larger rings, remove water to shift
  equilibrium toward products

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Polyesters

• Dacron thread
• Mylar tape

• Glyptal resin
• PET bottles

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Synthesis of Amides
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Reactions of Amides
acid and amine
amine
1 amine
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Lactam Formation

• Five- and six-membered rings can be formed by
  heating ?- and ?-amino acids.

• Smaller or larger rings do not form readily.
  
  gt

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?-Lactams

• Highly reactive, 4-membered ring.
• Found in antibiotics isolated from fungi.

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Polyamides
Nylon 6.6
gt
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Synthesis of Nitriles
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Reactions of Nitriles
1 amine
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Thioesters

• More reactive than esters because
• -S-R is a better leaving group than -O-R
• Resonance overlap is not as effective.

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Carbonic Acid Esters

• CO2 in water contains some H2CO3.
• Diesters are stable.
• Synthesized from phosgene.

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Urea and Urethanes

• Urea is the diamide of carbonic acid.
• Urethanes are esters of a monoamide of carbonic
  acid.

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Polycarbonates

• Long-chain esters of carbonic acid

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Polyurethanes

• A diol reacts with a diisocyanate.

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End of Chapter 21