Chapter 19 19'119'5 Carboxylic Acids

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Chapter 19( 19.1-19.5)Carboxylic Acids
19.1 Naming RCO2H 19.2 Bonding Structure 19.3
Boiling point Solubility 19.4 Acidity 19.5
Carboxylates
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Name the parent alkane stem then add -oic
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Name the parent alkane stem then add -oic
Systematic Name
Common Name
methanoic acid
formic acid
acetic acid
ethanoic acid
octadecanoic acid
stearic acid
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Indicate the locant and substituent name for
substituted RCO2H
Systematic Name
Common Name
2-hydroxypropanoicacid
lactic acid
(Z)-9-octadecenoicacid
oleic acid
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19.2Structure and Bonding
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Which bond is stronger CO or C-O?
What is the geometry at the CO2H group?
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Electron Delocalization

• stabilizes carbonyl group

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19.3Physical Properties
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Boiling Points
bp (1 atm)
31C
80C
99C
How can hydrogen bonding be used to explain the
increase in boiling point here?
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Hydrogen-bonded Dimers
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Solubility in Water

• RCO2H solubility similar to ROH solubility

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19.4Acidity of Carboxylic Acids

• pKa of RCO2H is ?

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Carboxylic acids are weak acids

• Compare the acidity for the compounds below

CH3CH2OH
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Carboxylic acids are weak acids

• but carboxylic acids gtgt alcohols in terms of
  acidity

CH3CH2OH
pKa 4.7
pKa 16
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Greater acidity of carboxylic acids is
attributedstabilization of carboxylate ion by
inductive effect of carbonyl group
resonance stabilization of carboxylate ion
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Figure 19.4 Electrostatic potential maps
ofacetic acid and acetate ion
Acetic acid
Acetate ion
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19.5Carboxylates
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Carboxylic acids are neutralized by strong bases


RCOH
HO
RCO
H2O
strongeracid
weakeracid

• K is 1011
• Lower molecular weight carboxylates are H2O
  soluble

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Carboxylic acids are neutralized by strong bases

• K for the equlibrium is 1011
• Lower mol. wt. carboxylates are H2O soluble
• Higher mol. wt. carboxylates form structures
• called micelles

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Micelles
sodium stearate(sodium octadecanoate)

Na
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Micelles
ONa
polar
nonpolar
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Micelles
ONa
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Micelles
ONa
Polar head (Hydrophilic)
Nonpolar tail (Hydrophobic)
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Figure 19.6 (p. 800) A micelle
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Micelles

• interior is nonpolar.
• Mechanism for how soaps clean
• e.g Grease dissolves in the interior of the
  micelle and is washed away with the dispersed
  micelle.