carboxylic acids acids have a sour or tart taste –examples: vinegaracetic acid lemonscitric acid...
Post on 22-Dec-2015
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Carboxylic Acids
Acids have a sour or tart taste– Examples:
• Vinegar acetic acid
• Lemons citric acid
• Tart apples malic acid
R
O
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 Formic acid Methanoic acid2 Acetic acid Ethanoic acid3 Propionic acid Propanoic acid4 Butyric acid Butanoic acid5 Valeric acid Pentanoic acid6 Caproic acid Hexanoic acid
http://www.youtube.com/watch?v=AntCzWw-28s
Remembering Nomenclature
• Formic acid… “ant acid”• Acetic acid……. “acetum”
(Latin=vinegar)
• Butyric acid…….. “butter acid”
• Caproic acid………. “goat acid”
• Unbranched 3-10……. “fatty acids”
Physical Properties
• Highest bp of compounds studied so far!
Alcohols
Alkyl halidesAlkanes
Incr
easi
ng B
P
Ethers/Aldehydes/Ketones
Carboxylic acids
Physical Properties
• Higher boil points due to hydrogen bonding and
• Carboxylic acid dimers– Two identical units
C
O
O
R
H
C
O
O
R
H
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 PointsSaturated 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
C
C
C
O C
O
O C
O
O C
O
H
H
H
H
H
+ NaOH3
C
O
ONa+
3
+H
H OH
OHH
OHH
Hfat or oil
glycerol
soap
Soap
C
O
ONa+
soap
polar non polar
Soap Micelles
O
O
OO O
O O O
OO
O
O
O
O
O
O
Modern Detergents
Dodecylbenzene Sodium 4dodecylbenzenesulfonate
CH2(CH2)10CH2
H2SO4
NaOHCH2(CH2)10CH2 SO3-Na+
Acidity due to Electron Withdrawing Groups
O
OH
H
HH
O
OH
H
HCl
O
OH
Cl
ClCl
PKa = 4.76 Pka = 2.86 PKa = 0.70
Carboxylic Acid Reactions
O
OHLiOH
O
O Li+ OH2
O
OH NH3
O
O NH4+
+ +
+
React as an acid with a base
Separation using soluble salts
Reduction To an Alcohol
O
OH
LiAlH4Ether
OH2
CH2OHLiOH Al(OH)3+ +
Reduction is difficult for acids, but Lithium Aluminum Hydride will do it
Fischer Esterification
O
OH
O
O OH2OH
H2SO4
+ +
Decarboxylation
O
OH
HeatCO2+