Chapter 21 Carboxylic Acid Derivatives (continued) Jo Blackburn Richland College, Dallas, TX Dallas...
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Chapter 21 Carboxylic Acid Derivatives (continued) Jo Blackburn Richland College, Dallas, TX Dallas County Community College District 2006, Prentice Hall Organic Chemistry, 6 th Edition L. G. Wade, Jr.
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Transcript of Chapter 21 Carboxylic Acid Derivatives (continued) Jo Blackburn Richland College, Dallas, TX Dallas...
Chapter 21Carboxylic Acid Derivatives
(continued)
Jo BlackburnRichland College, Dallas, TX
Dallas County Community College District2006,Prentice Hall
Organic Chemistry, 6th EditionL. G. Wade, Jr.
Chapter 21 2
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.
=>
Chapter 21 3
Acid Hydrolysis of Esters
• Reverse of Fischer esterification.
• Reaches equilibrium.
• Use a large excess of water.
+CH3 C
O
OCH3 HOH CH3 C
O
OH + CH3OHH+
=>
Chapter 21 4
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. =>
Chapter 21 5
Hydrolysis of Amides
Prolonged heating in 6 M HCl or 40% aqueous NaOH is required.
=>
Chapter 21 6
Hydrolysis of Nitriles• Under mild conditions, nitriles hydrolyze
to an amide.
• Heating with aqueous acid or base will hydrolyze a nitrile to an acid.
=>
Chapter 21 7
Reduction to Alcohols
Lithium aluminum hydride reduces acids, acid chlorides, and esters to primary alcohols.
=>
Chapter 21 8
Reduction to Aldehydes
Acid chlorides will react with a weaker reducing agent to yield an aldehyde.
=>
Chapter 21 9
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.
=>
Chapter 21 10
Organometallic Reagents
Grignard reagents and organolithium reagents add twice to acid chlorides and esters to give alcohols after protonation.
=>
Chapter 21 11
Grignard Reagentsand Nitriles
A Grignard reagent or organolithium reagent attacks the cyano group to yield an imine which is hydrolyzed to a ketone.
=>
Chapter 21 12
Acid Chloride Synthesis
• Use thionyl chloride, SOCl2, or oxalyl chloride, (COCl)2.
• Other products are gases.
=>
Chapter 21 13
Acid Chloride Reactions (1)
acid
ester
amide
acid anhydride =>
Chapter 21 14
Acid Chloride Reactions (2)
3° alcohol
ketone
1° alcohol
aldehyde
acylbenzene =>
AlCl3
Chapter 21 15
Industrial Synthesis of Acetic Anhydride
• Four billion pounds/year produced.
• Use high heat (750°C) and triethyl phosphate catalyst to produce ketene.
CH3 C
O
OH(EtO)3P O
heat
CH
HC O
CH
HC O + CH3 C
O
OH CH3 C
O
O C
O
CH3
=>
Chapter 21 16
Lab Synthesisof Anhydrides
• React acid chloride with carboxylic acid or carboxylate ion.
C
O
Cl+ CH3 C
O
O_ C
O
O C
O
CH3
• Heat dicarboxylic acids to form cyclic anhydrides. C
O
OH
C
O
OHO
O
O=>
Chapter 21 17
Anhydride Reactions
acid
ester
amide
=>
acylbenzeneAlCl3
Chapter 21 18
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.
C
O
OCH2CH3
C
O
OHO
O
O
CH3CH2OH=>
Chapter 21 19
Synthesis of Esters
R C
O
OR'R C
O
OH + R'OHH+
+ HOH
acid
R C
O
OR'R C
O
Cl + R'OH + HCl
acid chloride
R C
O
OR'R C
O
O C
O
R + R'OHH+
+ RCOOH
acid anhydride
R C
O
OH CH2N2+ R C
O
OCH3 N2+methyl ester =>
Chapter 21 20
Reactions of Esters
acid
ester
amide
1° alcohol
3° alcohol=>
Chapter 21 21
Lactones• Formation favored for five- and six-
membered rings.O
OCOOH
OH H+
H2O+
• For larger rings, remove water to shift equilibrium toward products
H+
H2O+O
O
OH
COOH
=>
Chapter 21 22
Polyesters
• Dacron® thread• Mylar® tape
• Glyptal resin• PET bottles
=>
Chapter 21 23
Synthesis of AmidesR C
O
OH + HOH+ R'NH2heat
R C
O
NHR'
acid
R C
O
O C
O
R + RCOOHR'2NH R C
O
NR'2+acid anhydride
R C
O
OR'' + R''OHR'NH2 R C
O
NHR'+ester
R C
O
NH2R C N + H2OH+ or OH-
nitrile =>
acid chlorideR'2NH2
+Cl-+R C
O
NR'2R'2NH+ 2R C
O
Cl
Chapter 21 24
Reactions of Amides
acid and amine
amine
1° amine
=>
nitrile
Chapter 21 25
Lactam Formation• Five- and six-membered rings can be
formed by heating - and -amino acids.
• Smaller or larger rings do not form readily. =>
Chapter 21 26
-Lactams
• Highly reactive, 4-membered ring.
• Found in antibiotics isolated from fungi.
Amide ester !!
=>
Chapter 21 27
Polyamides
Nylon 6.6
=>
Chapter 21 28
Synthesis of Nitriles
R C
O
NH2 R C NPOCl3
1° amide
R C N +R X NaCN Na+X-
alkyl halide
+Ar N N+ CuCN Ar CN N2
diazonium salt
R C
O
R'HCNKCN
R C R'
HO CN
aldehyde or ketone
cyanohydrin =>
Chapter 21 29
Reactions of Nitriles
ketone
=>
amide acid
1° amine
Chapter 21 30
ThioestersMore reactive than esters because:
-S-R is a better leaving group than -O-RResonance overlap is not as effective.
=>
Chapter 21 31
Carbonic Acid Esters
• CO2 in water contains some H2CO3.
• Diesters are stable.
• Synthesized from phosgene.
+C
O
ClCl CH3CH2OCOCH2CH3
O
2 CH3CH2OH
diethyl carbonate
=>
phosgene
Chapter 21 32
Urea and Urethanes
• Urea is the diamide of carbonic acid.
• Urethanes are esters of a monoamide of carbonic acid.
+C
O
ClCl C
O
NH2H2N2 NH3urea
N C O
H2ONH C OH
O
a carbamic acid
ROHNH C OR
O
a urethane =>
Chapter 21 33
Polycarbonates
Long-chain esters of carbonic acid
=>
Chapter 21 34
Polyurethanes
A diol reacts with a diisocyanate.
=>
Chapter 21 35
End of Chapter 21
