Carboxylic Acids
Acids have a sour or tart taste
– Examples:
• Vinegar
• Lemons
• Tart apples
acetic acid
citric acid
malic acid
O
R
OH
-COOH
-CO2H
Nomenclature
•
•
Drop the e and ad oic acid
If two acid groups in a molecule – keep the e and say
dioic acid
–
–
Carbonyl C is always is number 1 carbon
Also called an “acyl” group
C OH
O
Practice some on the board
Nomenclature
#C
Common Name
IUPAC Name
1
2
3
4
5
6
Formic acid
Acetic acid
Propionic acid
Butyric acid
Valeric acid
Caproic acid
Methanoic acid
Ethanoic acid
Propanoic acid
Butanoic acid
Pentanoic acid
Hexanoic acid
http://www.youtube.com/watch?v=AntCzWw-28s
Remembering Nomenclature
•
•
•
•
•
Formic acid…
Acetic acid…….
Butyric acid……..
Caproic acid……….
Unbranched 3-10…….
“ant acid”
“acetum” (Latin=vinegar)
“butter acid”
“goat acid”
“fatty acids”
Physical Properties
Increasing BP
• Highest bp of compounds studied so far!
Carboxylic acids
Alcohols
Ethers/Aldehydes/Ketones
Alkyl halides
Alkanes
Physical Properties
• Higher boil points due to hydrogen bonding
and
• Carboxylic acid dimers
– Two identical units
O H
R
O
C
C
O
H O
R
Physical Properties
– Foul odors
• butyric acid
stale perspiration
locker room odor, rancid butter
• valeric acid
smells worse (goat smell)
From Yahoo Images
Solubility of Organics
• One electronegative group per four carbons
will make a compound dissolve in water
Fatty Acids
•
•
•
•
•
•
Long un-branched carboxylic acids
Most have between 12 and 20 carbons
Derived from the hydrolysis of fats
Most have an even number of C’s
If unsaturated, the cis isomer predominates
Unsaturated have lower melt points than saturated
Melting Points
Saturated have higher melting points than
unsaturated fatty acids
Soap
• Soap is made by adding NaOH to a fat
• This reaction is called soponification
• This cleaves each of the fatty acids
producing the solid fatty acid salt (soap)
• The other product is glycerol
soap
O
H
3 Na
O
H
C
O C
O
H
C
O C
O
H
C
O C
H
fat or oil
+
3 NaOH
+
O C
+
H
H
OH
H
OH
H
OH
H
glycerol
Soap
O
soap
+
Na O C
polar
non polar
Soap Micelles
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
Modern Detergents
CH2(CH2)10CH2
Dodecylbenzene
H2SO4
NaOH
CH2(CH2)10CH2
SO3-Na+
Sodium 4dodecylbenzenesulfonate
Acidity due to Electron
Withdrawing Groups
H
H
O
OH
H
PKa = 4.76
H
H
Cl
O
Cl
OH
Pka = 2.86
Cl
Cl
O
OH
PKa = 0.70
Carboxylic Acid Reactions
React as an acid with a base
O
O
OH
+
LiOH
O
O Li
O
OH
+
NH3
O NH4+
+
+
H2O
Separation using soluble salts
Reduction To an Alcohol
Reduction is difficult for acids, but
Lithium Aluminum Hydride will do it
O
LiAlH4 Ether
OH
H2O
CH2OH
+
LiOH
+ Al(OH)3
Fischer Esterification
O
OH
+
OH
H2 SO4
O
O
+
H2O
Decarboxylation
O
Heat
OH
+
CO2