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Chapter Sixteen

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Title: Chapter Sixteen


1
Chapter Sixteen
  • Carboxylic Acids, Esters, and Other Acid
    Derivatives

2
  • Carboxylic acid An organic compound with
    carboxyl functional group
  • Carboxyl group A carbonyl group (CO) with a
    hydroxyl group (OH) bonded to the carbonyl
    carbon atom
  • A general structural representation for a
    carboxyl group is shown below

Carbonyl group
Carboxylic acid
3
Carboxylic Acids
  • Fig. 16.1
  • The three simplest carboxylic acids methanoic
    acid, ethanoic acid, and propanoic acid.

4
Carboxylic Acids
  • Fig. 16.2
  • Benzoic acid molecule

5
Carboxylic Acids
  • Carboxylic acids always contain the carboxyl
    group on __________ ____.
  • A carboxyl group is a carbonyl attached to a
    hydroxyl
  • Acts differently than an alcohol or a carbonyl
    compound
  • O
  • ??
  • CH3 COH CH3COOH
  • carboxyl group

6
IUPAC Rules for Naming Monocarboxylic Acids
  • Rule 1 Select the longest carbon chain that
    includes the carbon atom of the carboxyl group as
    the parent chain.
  • Rule 2 Name the parent chain by changing the
    -e ending of the corresponding alkane to -oic
    acid.
  • Rule 3 Number the parent chain by assigning the
    1 to the carboxyl carbon atom.
  • Rule 4 Determine the identity and location of
    any substituents in the usual manner, and append
    this information to the front of the parent chain
    name.

7
Naming Rules
  • Identify longest chain containing the ___________
    group
  • (IUPAC) Number ____________ carbon as 1
  • (Common) Assign ?, ?, g to carbon atoms adjacent
    to ____________ carbon
  • CH3
  • CH3 CHCH2 COOH
  • IUPAC 3-methylbutanoic acid
  • Common ?-methylbutryic acid

8
Naming Carboxylic Acids
  • Formula IUPAC Common
  • alkan -oic acid prefix ic acid
  • HCOOH methanoic acid formic acid
  • CH3COOH ethanoic acid acetic
    acid
  • CH3CH2COOH propanoic acid propionic
    acid
  • CH3CH2CH2COOH butanoic acid
    butyric acid

9
First Six Unbranched Monocarboxylic Acids
10
First Six Unbranched Dicarboxylic Acids
11
Aromatic Carboxylic Acids
  • Benzoic Acid is the ______________ carboxylic
    acid
  • Locates substituents by assigning 1 to the carbon
    with the carboxyl group

3-chlorobenzoic acid
Benzoic acid
4-methylbenzoic acid
12
Common Acids
  • Acetic Acid CH3COOH
  • Vinegar is 4-8 (v/v) acetic acid solution
  • Colorless liquid with sharp odor
  • Oxalic acid HOOC-COOH - found in spinach and
    cabbage
  • Harmful at high concentrations
  • Used to remove rust, bleach straw, and leather
    and ink stains

13
Polyfunctional Carboxylic Acids
  • PCAs contain at least one or more functional
    groups other than carboxyl group
  • PCAs are commonly found in living organisms an
    play an important role in human body
  • Occur in many fruits
  • Used in over the counter skin care products and
    prescription drugs
  • Common types of PCAs
  • Unsaturated acids
  • Hydroxy acids
  • Keto acids

14
Unsaturated Acids
  • Contain at least one carbon-carbon double bond
    (CC)
  • Two types of monounsaturated carboxylic acids
  • Trans - unsaturated carboxylic acids
  • Cis unsaturated carboxylic acids
  • Examples
  • Propenoic acid (acrylic acid) used in the
    manufacture of polymeric materials.
  • Futenedioic acid - has two forms
  • Fumaric acid trans-form
  • Maleic acid cis-form

15
Hydroxy Acids
  • Contain at least one hydroxyl group and are
    naturally present in many foods
  • Examples
  • Glycolic acid present in juice from sugar cane
    and sugar beets
  • Lactic acid Present sour milk, sauerkraut, and
    dill pickles
  • Malic acid and tartaric acid occur naturally in
    fruits

16
Keto Acids
  • Contain a carbonyl (CO) group within a carbon
    chain.
  • Example
  • Pyruvic acid - simplest keto acid with odor
    resembling that of vinegar (acetic acid) and it
    is also a metabolic acid

17
  • Metabolic acids Polyfunctional acids formed as
    intermediates of ________________ reactions in
    the human body.
  • There are eight such acids that will appear
    repeatedly in the biochemistry chapters
  • Metabolic acids are derived from
  • Propionic acid, (C3 mono acids) lactic,
    glyceric, and pyruvic acids
  • Succinic acid (C4 diacid) fumaric, oxaloacetic,
    and malic acids
  • Glutaric acid (C5 diacid) a-ketoglutaric and
    citric acids

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19
At Room Temperature and Pressure
  • Straight chain carboxylic acids with 1-9 carbon
    atoms are liquids and strong odors
  • Straight chain carboxylic acids with gt10 C atoms
    are waxy solids with no odor.
  • Aromatic and dicarboxylic acids Odorless solids

20
Properties of Carboxylic Acids
  • Like alcohols, carboxylic acids form ___________
    intermolecular hydrogen bonds.
  • Most carboxylic acids exist as ___________.
  • Boiling points higher than alkanes of similar MW.
  • Small carboxylic acids (1-4 carbons) are soluble
    in water

21
Boiling Points
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23
Synthesis of Carboxylic Acids
  • Synthesized from aromatic rings, primary
    alcohols and aldehydes.
  • Oxidizing Agents
  • K2Cr2O7 / H2SO4
  • or
  • KMnO4

Carboxylic Acid
24
Oxidation of Aromatic Compounds
  • Benzene does not react with KMnO4.
  • Alkyl groups on the ring (-R) are readily
    oxidized though.
  • One product for all reactions.

25
Oxidation of Aromatic Compoundswith KMnO4
26
  • Oxidation of primary alcohols and aldehydes

27
  • Oxidation of alcohols to carboxylic acids.

28
Properties
  • Carboxylic acids are ________ acids
  • Stronger acids than alcohols
  • In water they dissociate to release ___________
    (H) and form carboxylate ion (RCOO-) --
    equilibrium reactions and equilibrium lies
    towards the left indicating that small amount of
    acid is ionized
  • CH3COOH H2O CH3COO H3O
  • Neutralized by a base
  • CH3COOH NaOH CH3COO Na H2O

29
  • Monocarboxylic acids release ______ H to form
    carboxylate ion with _______ negative charge
  • Dicarboxylic acids release ______ H ions to form
    carboxylate ion with _____ negative charges and
    so on

30
  • Carboxylic acids are obviously _________.
  • Stronger acids than alcohols, but __________ than
    mineral acids.
  • Will react with _________ to give metal
    carboxylates.
  • There is a large range of acidities depending on
    the substituents on a carboxylic acid.

31
Carboxylate Ions
  • The conjugate base of a carboxylic acid
  • Formed when a carboxylic acid loses a proton
  • Named by dropping the -ic acid ending and
    replacing it with ate
  • CH3CH2COO- Propionate
  • CH3COO- Ethanoate (Acetate)
  • CH3CH2CH2COO- Butanoate

32
Carboxylate Salts
  • An ionic compound in which the negative ion is a
    carboxylate ion
  • Naming the positive ion is named first,
    followed by a separate word giving the name of
    the negative ion
  • Converted back to a carboxylic acid by the
    addition of a strong acid
  • CH3CH2COO-Na Sodium Propionate
  • CH3COO-K Potassium Ethanoate
  • CH3CH2CH2COO-Li Lithium Butanoate

33
Uses of Carboxylic Acid Salts
  • Good antimicrobial and antifungal agents
  • Benzoate salts Effective (0.1, m/m) against
    yeast and mold in beverages, jams and jellies,
    etc.
  • Sodium sorbate Inhibits mold and yeast in dairy
    products, dried fruits, some meat and fish
    products
  • Propionate Used in preservation of baked goods
  • Benzoate and sorbate cant be used in yeast
    leavened baked goods as they inhibit mold and
    yeast

34
Carboxylic Acids
35
Esters
  • Fig. 16.12
  • Methyl and ethyl esters of acetic acid.

36
Ester
  • In an ester, the _______ in the carboxyl group is
    replaced with an ________ group
  • O
  • ??
  • CH3 CO CH3 CH3COO CH3
  • ester group
  • Sulfur analogs of esters are called thioesters
    (sulfur replaces the hydroxyl oxygen)

37
  • The name for the alcohol part of the ester
    appears _________ and is _____________ by a
    separate word giving the name for the acid part
    of the ester.
  • The name for the alcohol part of the ester is
    simply the name of the R group (alkyl,
    cycloalkyl, or aryl) present in the OR portion
    of the ester.
  • The name for the acid part of the ester is
    obtained by dropping the -ic acid ending for
    the acids name and adding the suffix -ate.

38
Naming Esters
  • Name the alkyl from the alcohol O-
  • Name the acid with the CO with ate
  • acid alcohol
  • O
  • ?? methyl
  • CH3 CO CH3
  • Ethanoate methyl ethanoate (IUPAC)
  • (acetate) methyl acetate (common)

39
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40
Esters
41
Esterification Preparation of Esters
  • Reaction of a carboxylic acid and alcohol
  • Acid catalyst
  • O
  • ?? H
  • CH3 COH HOCH2CH3
  • O
  • ??
  • CH3 COCH2CH3 H2O

42
Hydrolysis Breaking Up Esters
  • Esters react with water and acid catalyst
  • Split into carboxylic acid and alcohol
  • O
  • ?? H
  • H COCH2CH3 H2O
  • O
  • ??
  • H COH HOCH2CH3

43
Hydrolysis
44
Saponification
  • Esters react with bases
  • Produce the salt of the carboxylic acid and
    alcohol
  • O
  • ?? H2O
  • CH3COCH2CH3 NaOH
  • O
  • ??
  • CH3CO Na HOCH2CH3
  • salt of carboxylic acid
  • Saponification reactions produce soaps

45
Soaps
  • Carboxylate salts

46
  • The following figure represents soap.
  • Which end of the anion is hydrophobic?

47
  • How does soap interact with grease?

48
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51
Dicarboxylic Acids
52
The C2 dicarboxylic acid, oxalic acid,
contributes to the tart taste of rhubarb stalks.
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