Transcript Chapter 11: Reactions at an sp3 Hybridized Carbon III

Carbonyl Compounds I:
Chapter 11
Chapter 11
1
Contents of Chapter 11
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Naming Carboxylic Acids and Derivatives
Physical Properties of Carbonyl
Compounds
Reactivity of Carboxylic Acid Derivatives
Reactions of Carboxylic Acids and
Derivatives
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IUPAC Nomenclature of
Carboxylic Acids
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
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Select as the parent compound the
longest chain of carbon atoms that
contains the carboxyl group
Change the suffix –e of the parent name
to –oic acid
Carboxyl carbon is carbon 1
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Examples
CH3
4
CH3
O
CH
C
3
CH2
2
1
O
O
CH
3
H
3-Methylbutanoic acid
CH
C
1
O
H
2
3-Phenyl-2-propenoic acid
(cinnamic acid)
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Dicarboxylic Acids
Dicarboxylic acids are named by
adding the suffix –dioic acid to the
name of the parent compound that
contains both carboxyl groups
Chapter 11
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Examples
Chapter 11
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Aromatic Carboxylic Acids
CO2H
CO2H
benzoic acid
OH
2-hydroxybenzoic acid
(salicylic acid)
CO2H
CO2H
1,2-benzenedicarboxylic acid
(phthalic acid)
CO2H
HO2C
1,4-benzenedicarboxylic acid
(terephthalic acid)
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Derivatives of Carboxylic
Acids
R
O
O
O
C
C
C
Cl
R
an acid chloride
R
R
an anhydride
O
O
C
O
O
an ester
R
R
C
N
R
R
an amide
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Nomenclature
Acid chlorides are named by replacing the
–ic acid of the carboxylic acid with –yl
chloride.
O
O
CH3
C
C
Cl
Cl
O2N
acetyl chloride
4-nitrobenzoyl chloride
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Nomenclature
Anhydrides are named by adding the
word anhydride to the name of the
parent acid.
CH3
O
O
C
C
O
O
O
C
C
O
CH3
acetic anhydride
benzoic anhydride
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Nomenclature
•
•
Esters are named as a derivative of the
carboxylic acid from which it is derived.
The alkyl or aryl group attached to the
oxygen is named first.
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Nomenclature
Chapter 11
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Nomenclature
Amides are named as derivatives of their
carboxylic acid by dropping the suffix of the
acid and adding –amide.
O
CH3
C
CH3
NH2
acetamide
CH
O
O
C
C
NH2
CH3
2-methylpropanamide
NH2
benzamide
Note: the above amides are all primary (1o) amides.
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Nomenclature
If a hydrogen atom of an amide is replaced by an alkyl
or aryl group, the substituent is named and its location
on nitrogen indicated by N- (or N,N- if there are two
groups)
O
H
C
O
N
CH3
CH3
N,N-dimethylformamide
(a 3o amide)
CH3CH2CH2
C
N
H
N-phenylbutanamide
(a 2o amide)
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Physical Properties of
Carboxylic Acids
Carboxylic acids can form H-bonding molecule
pairs, so the boiling points of carboxylic acids
are somewhat higher than even alcohols with
the same molar mass because they often boil
away from the liquid as molecule pairs:


O
CH3
H O
C
C
O
H

Chapter 11
CH3
O
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Physical Properties of
Carboxylic Acids
O
CH3CH2CH2CH2OH
CH3CH2COH
propanoic acid
(propionic acid)
MW = 74; bp = 141oC
O
1-butanol
(n-butyl alcohol)
MW = 74; bp = 117oC
O
CH3CH2CH2COH CH3CH2CH2CH2CH CH3CH2CH2CH2CH2OH
butanoic acid
pentanal
1-pentanol
MW = 88
MW = 84
MW = 88
bp = 164oC
bp = 103oC
bp = 137oC
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Physical Properties of Amides
Hydrogen bonding is possible.
H
O
C
R
N
R
H
O
C
N
H
H
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Acidity of Carboxylic Acids
All carboxylic acids, whether soluble or
insoluble in water, react quantitatively with
NaOH, KOH, and other strong bases to
form salts
CO2H
CO2 Na
+ NaOH
benzoic acid
(only slightly soluble in H2O)
+ H2O
sodium benzoate
(very soluble in water)
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Preparation of Esters
A carboxylic acid can be converted to an ester by
heating with an alcohol in the presence of an acid
catalyst, usually concentrated sulfuric acid.
O
CH3
C
+ HOCH2CH3
OH
 /H
ethanol
acetic acid
O
CH3
C
O
CH2CH3 + H2O
ethyl acetate
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Stabilities of Carboxylic Acid
Derivatives
• In principle carboxylic acid derivatives should be able to be
interconverted into one another using a scheme like the one
shown below
• In the scheme below LG represents the original group, like OR,
attached to the starting compound (OR would make this an
ester)
• Nu (nucleophile) forces LG (leaving group) to leave and
replaces it, making a new compound
• In this scheme if Nu is amine and LG is alkoxy (OR) then an
ester is converted into an amide
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Stabilities of Carboxylic Acid
Derivatives
• Scheme on previous slide will only work if Nu is less stable than
LG, so reaction goes downhill
• Relative energy of Nu or LG given by pKa of conjugate acid
• In table below the derivatives at the top are less stable than
those beneath
• In neutral or basic media you can convert a derivative higher up
into one lower down, but not vice-versa
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Stabilities of Carboxylic Acid
Derivatives
• In acidic media interconversion of carboxylic acid derivatives
works by a different mechanism
• In this mechanism LG can be protonated before it leaves
• In this case the leaving group is no longer negatively charged
when it leaves; therefore it leaves more easily (more stable)
• In acidic media you can interconvert any of the carboxylic acid
derivatives into one another
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Reactions Carboxylic Acid
Derivatives
• To work out the product of a carboxylic acid derivative
reaction first make sure the reaction will work
• If the reaction is done in acid or goes from a less stable
derivative to a more stable derivative polarize the most
polar bonds in the reactants and swap partners
• Always polarize the carbonyl carbon positive and the
leaving group negative in these reactions
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