Carboxylic Acids and Their Derivatives -...
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Carboxylic Acids and Their Derivatives
Transcript of Carboxylic Acids and Their Derivatives -...
Carboxylic Acids and Their Derivatives
Families Containing the Carbonyl Group
O
CZY
O
CCO
Family Y Z
aldehyde H or C H
ketone C C
carboxylic acid H or C -O-H
ester H or C -O-C
acid halide H or C -F,-Cl,-Br,-I
acid anhydride H or C
amide H or C -N
Carboxylic Acid Functional Group
Carbonyl + hydroxyl = “Carboxyl”
General Formula: R-COOH R C O O H =
The carbonyl carbon and oxygen are sp2 hybridized. The hydroxyl oxygen is sp3 hybridized.
Sources of Carboxylic Acids
Oxidation of Primary Alcohols and Aldehydes
R C O HH
HR C O H
OR C
OH
primary alcohol aldehyde carboxylic acid
[O][O]
Substituted Benzenes as a Source of Substituted Benzoic Acids
CO O
H
Benzoic Acid
MnO4-
Cr2O72-
Nomenclature of Carboxylic Acids
Names of the Simplest Carboxylic Acids
Compound Systematic Name Trivial (Common) Name
HCOOH Methanoic Acid Formic Acid
CH3COOH Ethanoic Acid Acetic Acid
CH3CH2COOH Propanoic Acid Propionic Acid
CH3CH2CH2COOH Butanoic Acid Butyric Acid
CH3CH2CH2CH2COOH Pentanoic Acid Valeric Acid
CH3CH2CH2CH2CH2COOH Hexanoic Acid Caproic Acid
CH3CH2CH2CH2CH2CH2COOH Heptanoic Acid Enanthic Acid
Systematic Nomeclature
CH3CH2CH2CHCH2COOH
CH33-methyl hexanoic acid
β-methyl caproic acid
CH2CHCOOH
NH22-amino-3-phenylpropanoic acid
phenylalanine
Physical Properties of Carboxylic Acids
Boiling Points - Higher than alcohols of similar
molecular weight
Carboxylic acids “self associate” through hydrogen bonds.
R CO
O HRC
O
OH
Water Solubility- More water soluble than ethers,
aldehydes, ketones and alcohols of similar molecular weight
Carboxylic acids have three opportunities for hydrogen
bonding.
R CO
O H
HO
H
H3CCH2
C
O
O HO
H
H
H3CCH2
C
O
O
OH
HH
propanoic acidwater
propanoate ion
hydronium ion
Acidity of Carboxylic Acids
Acidity of Carboxylic AcidsCarboxylic acids are generally stronger acids than
phenols but weaker than mineral acids.
CH3C
O
O H
CH3C
O
O
OH
H
+ NaOH
Na+
Chemical and Physical Properties of Carboxylic Acids
Carboxylic acids react with bases.
acetic acid
sodium acetate
Carboxylate salts are ionic and possess much higher boiling and melting points than those of the corresponding carboxylic acids
(Ionic forces are much stronger than secondary forces).
Sodium acetate: MP 324°C, solid at room temperature Acetic acid: MP 17°C, liquid at room temperature
Carboxylic acids that have 6 or more carbons are only slightly soluble or insoluble in water. Carboxylate salts are much more soluble than
their corresponding carboxylic acids because of their ionic nature.
Chemical and Physical Properties of Carboxylic Acids
Carboxylic acids have increased solubilities in neutral or basic environments because the acids are converted into
their carboxylate ions.
H3CCH2
CH2
CH2CH2
CH2CH2
C
O
OH
+ NaOH
H3CCH2
CH2
CH2CH2
CH2CH2
C
O
O_
+ H2O
Na+
H3CCH2
CH2CH2
CH2CH2
CH2C
O
OH H3CCH2
CH2CH2
CH2CH2
CH2C
O
O_
Worksheet
CH3CH2 C
O
CH CH
CH3
CH3
OHa.
b.
CO
O H
Cl
H3C
H3C
1. Give an appropriate name for each compound.
2. Give structure(s) and name(s) for the major organic product(s) of the following reactions
a. _____________________________________ b. _____________________________________
CH3CH2 C
O
CH CH
CH3
CH3
OH NaOH, H2O
CO
O H
Cl
H3C
H3C KOH, H2O
Carboxylic Acid Esters
R C
O
OH R’HO R C
O
R’O+ + H2OH+
Synthesized from a carboxylic acid and an alcohol:
carboxylic acid alcohol or
phenol
ester
Nomenclature base on parent alcohol and carboxylic acid:
CH3 C
O
OH CH3HO CH3 C
O
CH3OCH2CH2 + + H2O
methanolpropanoic acid methyl propanoate
hydrolysis
condensation
Worksheet
Carboxylic Acid EstersAdditional Nomenclature examples:
CH3 C
O CH3
CH2O
CH3
CH
C
O
CH3CH2OCH3CH2CHCH2CH3
C
OCH3
CH O CH3CH2CH2CH3
isobutyl acetate
ethyl 3-methyl pentanoate
isopropyl butanoate
4. Give an appropriate name for each compound. a.
b.
c.
CO
O CH2F
F
CH3
COCH2 CH
CH3
CH3
O
OC
O
CH2 CHCH3
CH3
`ethyl 2,4-difluoro benzoate
Physical Properties of Esters
Ester molecules cannot hydrogen bond to each other.
Therefore, esters have much lower boiling and melting points than those of carboxylic acids.
Propanoic acid, bp 141°C Methyl acetate , bp 57°C
Esters are less soluble in water than are carboxylic acids because esters cannot form as many hydrogen bonds to
water molecules as can carboxylic acids.
CH3 C
O
OHCH2 CH3 C
O
CH3O
Physical Properties of Esters
The secondary forces in esters are weaker than those in aldehydes and ketones, and thus esters have lower melting
and boiling points.
Methyl acetate, bp 57°C Butanal, bp 76°C
Esters have about the same water solubilities as aldehydes and ketones because all three hydrogen bond to water equally well.
CH3 C
O
CH3O C
O
CH3CH2CH2 H
Esters Have Characteristic Odors
C
O
O C
O
OCH3C
O
OCH2CH3
Pear ApplePineapple
C
O
OHC
O
O
Raspberry Rum
C
O
O
Banana
C
O
O
C
O
OOrangePeach
Amides - Structure and Classification
Subclassification
C
O
NH
H
R1C
O
N
H
R1R2 C
O
NR1R2
R3
1º 2º 3º
Can amides engage in hydrogen bonding??
Amides - Structure and Classification
The amide is better represented as a dipolar ion:
C
O
N C
O
N
Because the bond between the carbonyl carbon atom and the nitrogen atom has a partial double bond character, the bond angles about the carbonyl carbon atom and nitrogen atom are both close to 120° (sp2 hybridization).
The dipolar ion nature of the amide bond is very important in determining the structure and function of protein molecules.
Amides - Synthesis
At low temperatures a carboxylic acid and an amine will take part in a simple acid-base reaction to form an ammonium salt.
R1 C
O
OH R2H N R1 C
O
O+R3
R2H N
R3
H
20-50o C
carboxylic amine ammonium acid carboxylate
Amides - Synthesis
At a higher temperature, a condensation reaction takes place between the carboxylic acid and the amine.
carboxylic ammonia primary acid amide
carboxylic 1º amine secondary acid amide
R1 C OH HH N+H
R1 C
O
H N
H>100o C
+ H2O
O
R1 C
O
OH R2H N+H
R1 C
O
R2 N
H>100o C
+ H2O
carboxylic 2º amine tertiary acid amide
R1 C
O
OH R2H N+R3
R1 C
O
R2 N
R3>100o C
+ H2O
Amides - Nomenclature
CH3C C
O
H N
HCH3
CH3
2,2-dimethyl propanamide
HN CH2CH2CH3C
O
N-propyl benzamide
Amides - Synthesis and Nomenclature
CH3 C
O
OH CH3H N+H
CH3 C
O
CH3 N
H>100o C+ H2O
acetic acid methylamine N-methylacetamide
NH2
C
O
OCH3C
O
CH3+
HN CH3C
O
+ CH3COOH
aniline acetic N-phenyl acetic anhydride acetamide acid
H CH2CH3CO
NCH2CH2CH3
NO2
CH2CH3CO
NH
HC
O
OHformic acid
CO
OH
benzoic acid
Amides - Physical Properties
Amides have the strongest secondary attractive forces and the highest melting and boiling points of any covalent organic compounds.
Potential Hydrogen Bonds:
R CO
N H
H
RCO
NH
H
Amides - Physical Properties
CH3 C
O
OHacetic acid
CH3 C
O
N
H
N-methylacetamide
CH3
CH3 C
O
N
H
acetamide
H
CH3 C
O
NN,N-dimethylacetamide
CH3
CH3
Amides - Physical Properties
The resonance structure of the amide functional group results in a large charge separation in an amide molecule resulting in large polarity and secondary attractive forces.
Amides - Comparison to Other Families
