10.carboxylic acids
TRANSCRIPT
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CHAPTER 10CARBOXYLIC ACIDS
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INTRODUCTION
The functional group of carboxylic acidsconsists of a C=O with -OH bonded to thesame carbon.
Carboxyl group is usually written -COOH.
Aliphatic acids have an alkyl group bondedto -COOH.
Aromatic acids have an aryl group bonded to
-COOH.
C
O
O H
C
O
O H
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IUPAC NAMES
Carbon atoms IUPAC name Chemical formula
1 Methanoic acid HCOOH
2 Ethanoic acid CH3COOH
3 Propanoic acid CH3CH2COOH
4 Butanoic acid CH3(CH2)2COOH
5 Pentanoic acid CH3(CH2)3COOH
6 Hexanoic acid CH3(CH2)4COOH
7 Heptanoic acid CH3(CH2)5COOH
8 Octanoic acid CH3(CH2)6COOH
9 Nonanoic acid CH3(CH2)7COOH
10 Decanoic acid CH3(CH2)8COOH
Remove -e from alkane (or alkene) name,add -oic acid.
The carbon of the carboxyl group is #1.
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OH group is indicated by the prefix hydroxy
3-hydroxypentanoic acid
NH2 group is indicated by amino
4-aminobutanoic acid
C O group of an aldehyde or ketone is indicated by oxo
4-oxobutanoic acid
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Dicarboxylic acids are named by adding thesuffix dioic acid
The number of the carboxyl carbons are notindicated..why???-they can be only at the ends of the parentchain.
Eg:
Ethanedioic acid Propanedioic acid
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Carboxylic acids bonded to cycloalkane ringis name by giving the name of the ring andadding the suffix carboxylic acid.
The atoms of the ring are numberedbeginning with the carbon bearing the COOH group.
Eg:
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1-Aminocyclopentanecarboxylic acid
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The simplest aromatic carboxylic acid is
benzoic acid. Derivatives are named by using numbers to
show the location of substituents relative tothe carboxyl group.
Eg:
Benzoic acid 2-hydroxybenzoic acid 1,2-benzenedicarboxylic acid
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IUPAC name COMMON name
Methanoic acid
Ethanoic acid
Propanoic acid
Butanoic acid
Pentanoic acid
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COMMON NAMES
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IUPAC name COMMON name
Methanoic acid Formic acid
Ethanoic acid Acetic acid
Propanoic acid Propionic acid
Butanoic acid Butyric acid
Pentanoic acid Valeric acid
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COMMON NAMES
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Oxidation of primary alcohols,aldehydes and alkyl benzene
Hydrolysis of nitriles Addition of grinard reagents to carbon
dioxide
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PREPARATION OF
CARBOXYLIC ACIDS
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Oxidation of Primary Alcohols, Aldehydes and
Alkyl Benzene
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Primary alcohol
Aldehydes
Alkyl benzene
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Hydrolysis of Nitriles The hydrolysis ofnitriles, which are organic
molecules containing a cyano group, leads tocarboxylic acid formation. These hydrolysis reactionscan take place in either acidic or basic solutions.
Eg:
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Addition of Grignard's reagent to
Carbon Dioxide
Grignards reagents react with carbon dioxide to formsalts of carboxylic acids which give carboxylic acids onacidification with mineral acids.
Eg:
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EXERCISES
1. Draw the Structural Formula for:a) 3,3-dimethylheptanoic acidb) 3-chloro-1,1-cyclopentanedicarboxylic
acid2. Complete these reactions.
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ACIDITY Weak acid The acidities: carboxylic acid > alcohol Both have O-H bond. Carboxylate ions are more stable.
Resonance stabilizes the carboxylate ions bydelocalizing its negative charge.
There is no comparable resonance stabilization ofalkoxide ions
Chapter 20 15
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Electron withdrawing groups attached to the carboxyl groupwould enhance acidity
Examples of acetic acid, chloroacetic acid and trichloroaceticacid
Chlorine atoms are electronegative and thus have anelectron withdrawing effect.
Thus they help stabilize the negative charge of the conjugate
base formed upon the ionization of an acid by electronwithdrawal through carbon-carbon bonds.
The greater the number of Cl atoms present, the greater thetotal electron withdrawing effect and the greater the ease of
ionization
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Aromatic ring substituents also influence the acidity ofcarboxylic acids
benzoic acid is more acidic than acetic acid, because itis capable of withdrawing electron density by induction Furthermore, benzoic acids with electron withdrawing
groups (i.e. NO2) are even "more acidic" than benzoicacid
Chapter 20 17
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EXERCISES
Which is the stronger acid in each pair
a) or
b) or
Chapter 20 18
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Reaction with bases Salt formation reaction of a carboxylic acid with an alkali
metal hydroxide (NaOH, LiOH, KOH)
Eg:
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CHEMICAL REACTIONS
OF CARBOXYLIC ACIDS
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EsterificationAn ester is formed when a carboxylic acid is refluxed with an
alcohol in the presence of a small amount of concentratedsulphuric acid as a catalyst
Eg:
Chapter 20 20
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Oxidation Methanoic acid is a strong reducing agent. It can decolurise
aqueous pottasium manganate (VII) at room temperature
HCOOH + [O] CO2 + H2O
Oxidation of ethanedioic acid occurs rapidly at 60 C
COOH + [O] CO2 + H2OCOOH
Chapter 20 22
KMnO4
KMnO4
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Chapter 20 23
Reduction
Dehydration of methanoic acid can be carried out bywarming it with concentrated sulphuric acid. Carbonmonoxide gas, which is combustile, is released.
HCOOH CO + H2O
Dehydration of ethanedioic acid can also be carried out byusing concentrated sulphuric acid under the same condition
COOH
CO + CO2
+ H2
OCOOH
H2SO4Warm
H2SO4
Warm
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INDUSTRIAL USES
Widely used as foods and drink preservatives Responsible for preventing the growth of bacteria,
fungus and various microorganisms Eg: sodium benzoate, calcium propanoate and
monosodium glutamate Sodium salts of long chained fatty acids, which canbe derived from fats and oils, are used in themanufacture of soap and detergents
Zinc undercylate can be used to make components ofbaby powder
Chapter 20 24
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EXERCISES
Butanenitrile is boiled with dilutesulphuric acid to form compound W. Wreacts with sulphur oxide dichloride toproduce X. X reacts with ethanol toproduce a sweet smelling liquid, Y.
Determine the structural formulae of W,X, Y.
Chapter 20 25
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