Post on 06-Jan-2016
description
Chapter 11 1
Carbonyl Compounds I:Carbonyl Compounds I:Chapter 11Chapter 11
Chapter 11 2
Contents of Chapter 11 Naming Carboxylic Acids and Derivatives Physical Properties of Carbonyl
Compounds Reactivity of Carboxylic Acid Derivatives Reactions of Carboxylic Acids and
Derivatives
Chapter 11 3
IUPAC Nomenclature of Carboxylic Acids
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
Chapter 11 4
Examples
CH3
CHCH3 CH2
C
O
OH
CHCH
C
O
OH
3-Methylbutanoic acid 3-Phenyl-2-propenoic acid(cinnamic acid)
12
34
12
3
Chapter 11 5
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 6
Examples
Chapter 11 7
Aromatic Carboxylic AcidsCO2H CO2H
OH
CO2H
CO2H
CO2H
HO2C
benzoic acid 2-hydroxybenzoic acid
1,2-benzenedicarboxylic acid 1,4-benzenedicarboxylic acid
(salicylic acid)
(phthalic acid) (terephthalic acid)
Chapter 11 8
Derivatives of Carboxylic Acids
O
CR O
C
O
R
O
CR O
R
O
CR N
R
R
O
CR Cl
an acid chloride an anhydride
an ester an amide
Chapter 11 9
Nomenclature
Acid chlorides are named by replacing the –ic acid of the carboxylic acid with –yl chloride.
O
CCH3 Cl
C
O
Cl
O2N
acetyl chloride 4-nitrobenzoyl chloride
Chapter 11 10
Nomenclature
Anhydrides are named by adding the word anhydride to the name of the parent acid.
O
CO
C
OO
CCH3 O
C
O
CH3
acetic anhydride benzoic anhydride
Chapter 11 11
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.
Chapter 11 12
Nomenclature
Chapter 11 13
Nomenclature
Amides are named as derivatives of their carboxylic acid by dropping the suffix of the acid and adding –amide.
O
CCH3 NH2
O
CNH2
O
CNH2CH
CH3
CH3
acetamide benzamide2-methylpropanamide
Note: the above amides are all primary (1o) amides.
Chapter 11 14
NomenclatureIf 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
CH N
CH3
CH3
O
CCH3CH2CH2 N
H
N,N-dimethylformamide N-phenylbutanamide(a 3o amide) (a 2o amide)
Chapter 11 15
Physical Properties of Carboxylic AcidsCarboxylic 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:
δ+
δ+
δ−
δ−
CH3 C
O
O
H
CH3C
O
OH
Chapter 11 16
Physical Properties of Carboxylic Acids
CH3CH2CH2CH2OH CH3CH2COH
O
propanoic acid 1-butanol (propionic acid) (n-butyl alcohol)MW = 74; bp = 141oC MW = 74; bp = 117oC
CH3CH2CH2CH2CH2OH CH3CH2CH2CH2CH
O
CH3CH2CH2COH
O
butanoic acid MW = 88
pentanalMW = 84
1-pentanol MW = 88
bp = 164oC bp = 103oC bp = 137oC
Chapter 11 17
Physical Properties of Amides
Hydrogen bonding is possible.
C
R
O NH
H
R
CO N
H
H
Chapter 11 18
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
+ H2O + NaOH
benzoic acid(only slightly soluble in H2O)
sodium benzoate(very soluble in water)
Chapter 11 19
Preparation of EstersA 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
CCH3 OH
O
CCH3 O
CH2CH3
+ HOCH2CH3/H
+ H2O
Δ
acetic acid
ethanol
ethyl acetate
Chapter 11 20
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
Chapter 11 21
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
Chapter 11 22
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
Chapter 11 23
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