Chapter 20' Carboxylic Acids

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Chapter 20. Carboxylic Acids

• Properties
• 1. Acidic!!

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2. Addition to carbonyl group
3. Protonation - two possibilities
Always favored!!
(why?)
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4. Hydrogen bonding
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B. Spectroscopic properties 1. IR O-H stretch
very broad, intense 2500 - 3500 cm-1 CO
stretch intense 1700 cm-1 2. 1H NMR RCO2H 10
- 13 ppm - broad Disappears upon addition of D2O -
Exchanging protons
3. 13C NMR OC 180 ppm
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C. Nomenclature 1. Common names - very prevalent
- -C(O)OH carboxyl group
acid common name
derivation HCO2H
formic acid formica - Lt. ant CH3CO2H
acetic acid acetum -
Lt. vinegar CH3CH2CO2H propionic acid protos
pion - Gk. dairy fat CH3(CH2)2CO2H butyric
acid butyrum- Lt. rancid butter CH3(CH2)3CO2H val
eric acid valerian - Lt. smelly
root CH3(CH2)4CO2H caproic acid caper - Lt. goat
oder
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other common names
2. IUPAC names - drop e in alkane name, replace
with oic acid. Number starting from
carboxyl carbon
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3. IUPAC for cycloalkanecarboxylic acids
4. IUPAC for dicarboxylic acids - just add dioic
acid to end of parent alkane name.
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D. Uses - not so many - derivatives - esters
amides are much more important.
O2
sugars CH3CH2OH
CH3CO2H (vinegar!)
fermentation
fermentation
lye
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micelle
hydrophillic region
hydrophobic region
M Ca2 or Mg2
soap scum
detergents
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DIRT!!
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E. Synthesis of carboxylic acids 1. Oxidation of
primary alcohols-
(chpt. 11-2)
2. Oxidation of alkynes with permanganate
3. Oxidation of alkynes with ozone
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4. Benzylic oxidation
(chpt 17-14)
5. Carboxylation of Grignard reagents a. overall
rxn.
b. mechanism
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c. examples
6. Synthesis and hydrolysis of nitriles
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F. Nucleophilic acyl substitution 1. overall
general reaction
We shall see that many of these reactions are
reversible
2. Fischer esterification a. overall reaction -
acid catalyzed
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b. mechanism
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c. To get a reasonable yield of ester we need
to use excess alcohol distill ester off as
soon as it is formed
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d. formation of lactones - must be 5 or 6
membered rings
G. Synthesis and uses of acid chlorides 1.
synthesis a. SOCl2 and PCl5
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b. oxalyl chloride and phosgene
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2. uses of acid chlorides a. general reactions
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b. general mechanism
Another example
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H. Esterification with diazomethane 1. overall
reaction
2. mechanism
3. example
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I. Direct condensation of carboxylic acids with
amines
1. general reaction
We can make this a much better reaction by 2.
DCC - dicyclohexylcarbodiimide
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Mechanism is basically-
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J. Preparation of anhydrides
a better procedure uses DCC or P2O5 to react
with the water formed
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K. Reduction of carboxylic acids 1. general
reaction
2. mechanism
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3. alternatives - we can stop at the aldehyde
stage by using bulky aluminum hydrides
L. Alkylation of carboxylic acids 1. general
reaction
Recall
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2. mechanism
NOTE
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M. Summary 1. Nomenclature - common IUPAC 2.
Spectroscopy 3. Synthesis of carboxylic acids
-review a. oxidation of alcohols b. oxidation
of alkynes c. benzylic oxidation 4.
Carboxylation of Grignard Reagents 5. Hydrolysis
of nitriles 6. Fisher esterification - mech. 7.
Syntheisi of acid chlorides (4 ways!) 8.
Synthetic uses of acid chlorides a. preparation
of esters b. preparation of amides c.
preparation of anhydrides d. reduction to
alcohols and aldehydes
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9. Esterification with diazomethane - mech. 10.
Condensation of acids with amines - use of
DCC 11. Reduction of carboxylic acids - mech. 12.
Alkylation of carboxylic acids - mech.