Chapter 14 in General, Organic, and Biological Chemistry, 7th edition, by Denniston.

1. Chapter 14
Carboxylic Acids and Derivatives
1

2. 1. Carboxylic acids
The carboxyl group consists of carbonyl and hydroxyl
groups attached to the same carbon.
carbonyl + hydroxyl = carboxyl
An aliphatic or aromatic group can be attached to the carboxyl
group.
2

3. 1. Carboxylic acids
The acyl group is a carboxyl group with either a hydroxyl
or alkoxy group.
If R is a hydroxyl group, the compound is a carboxylic acid.
If R is an alkoxy group, the compound is an ester.
3

4. 1. Carboxylic acids: boiling points
Intermolecular forces
are strong in carboxylic
acids due to
the high polarity of the
carboxyl group;
the presence of
hydrogen-bonding
between carboxylic acid
molecules.
4

5. 1. Carboxylic acids: boiling points
When two hydrogen bonds form between two carboxylic
acid molecules, the result is a dimer.
Dimer formation can cause carboxylic acids to seem to
have double their actual molecular mass.
5

6. 1. Carboxylic acids: boiling points
Compare molecules with similar molar masses and
different functional groups:
6

7. 1. Carboxylic acids: boiling points
Boiling point (oC) vs.
number of carbons for
acids, alcohols, aldehydes,
and alkanes.
7

8. 1. Carboxylic acids: solubility
Lower molecular weight carboxylic acids are very soluble
in water.
Vinegar is a solution of ethanoic acid.
Solubility falls off as molecular weight increases.
Why?
Hexadecanoic acid is insoluble in water.
8

9. 1. Carboxylic acids: solubility
Solubility (g acid/g H2O)
vs. number of carbons for
saturated, unbranched-
chain carboxylic acids.
9

10. 1. Carboxylic acids: nomenclature
Determine the parent compound from the longest
chain that includes the carboxyl carbon.
Number the chain so that the carboxyl carbon is
carbon 1.
Replace the –e ending with –oic acid.
Assign numbers to any remaining substituents.
10

11. 1. Carboxylic acids: nomenclature
Additional notes:
If two carboxyl groups are present use –dioic acid.
For cycloalkanes, add carboxylic acid to the name of the
cycloalkane.
For aromatic acids, the simplest acid is benzoic acid.
If the acid group is attached to the aromatic ring, name after
benzoic acid.
If the acid group is not attached to the aromatic ring, name after
the longest chain, with a –phenyl substituent.
11

12. 1. Carboxylic acids: nomenclature
pencast
12

13. 1. Carboxylic acids: nomenclature
Name the following compounds:
pencast
13

14. 1. Carboxylic acids: nomenclature
Draw structures for the following compounds:
2,5-dimethylhexanoic acid
3-bromo-5-chlorooctanoic acid
pencast
2,2-dimethylbutanedioic acid
3-methylcyclohexanecarboxylic acid
2,4-dichlorobenzoic acid
3-phenylpentanoic acid
14

15. 1. Carboxylic acids
Is “alpha-hydroxy” an actual substance?
glycolic acid
α carbon
lactic acid
tartaric acid
15

16. 1. Carboxylic acids
The last paragraph in the inset box on pages 460-461 of
your textbook states:
"For the time being, biodegradable plastics cannot outcompete
their nonbiodegradable counterparts. Future research and
development will be required to reduce the cost of commercial
production and fulfill the promise of an 'environmentally
friendly' garbage bag.”
This statement gives the impression that there are no
biodegradable plastics available to consumers at a reasonable
cost.
Compostable plastic bags
16

17. 1. Carboxylic acids: reactions
Preparation is by complete oxidation of primary alcohols
or oxidation of aldehydes.
1o alcohol aldehyde carboxylic acid
17

18. 1. Carboxylic acids: reactions
Carboxylic acids are proton donors and therefore react as
acids.
Carboxylic acids are weak acids, dissociating only slightly
in solution.
>95% <5%
18

19. 1. Carboxylic acids: reactions
When a strong base is added to a carboxylic (weak) acid,
water and salt are formed.
Although the carboxylic acid isn’t initially completely
dissociated, as H+ is removed by reaction with OH-, more
acid dissociates.
19

20. 1. Carboxylic acids: reactions
Remember le Chatelier’s principle?
When product (H+) is removed, the equilibrium shifts to
make more product (and less undissociated acid).
20

21. 1. Carboxylic acids: reactions
Acid-base reaction
carboxylic acid + strong base  carboxylic acid salt + water
21

22. 1. Carboxylic acids: reactions
Naming salts of carboxylic acids
Name the carboxylic acid.
Replace the –ic acid ending with –ate.
Precede this name with the name of the cation.
Name the salts formed in the following reactions:
ethanoic acid + KOH
benzoic acid + LiOH pencast
hexanoic acid + NaOH
22

23. 1. Carboxylic acids: reactions
Esterification is the formation of water and an ester from
a carboxylic acid and an alcohol.
More about this in the next section…
23

24. 2. Esters
Esters are carboxylic acid derivatives, in which the acidic
-H of the acid has been replaced by an alkyl or aryl group
–R.
carboxylic acid ester derivative
24

25. 2. Esters: properties
Esters
are slightly polar;
boil at about the same temperature as corresponding
aldehydes and ketones;
are somewhat soluble in water when they are small.
have pleasant aromas.
25

26. 2. Esters: nomenclature
Recall nomenclature of salts of carboxylic acids.
Name the carboxylic acid.
Replace the –ic acid ending with –ate.
Precede this name with the name of the cation.
Esters are named in the same way, except the alkyl or aryl
portion of the alcohol is used in place of the cation name.
Name the carboxylic acid.
Replace the –ic acid ending with –ate.
Precede this name with the name of the alkyl or aryl portion of the
alcohol.
26

27. 2. Esters: nomenclature
Name the following esters.
pencast
27

28. 2. Esters: nomenclature
Draw the structures of the following esters.
propyl ethanoate
octyl decanoate
methyl methanoate
pencast
2-methylpropyl propanoate
3-methylbutyl ethanoate
phenyl pentanoate
28

29. 2. Esters: reactions
Preparation of esters is by reaction of a carboxylic acid
and an alcohol to produce an ester and water.
This is a dehydration reaction. [water is lost]
Heat and a trace of acid catalyst (H+) are required.
The reaction produces an equilibrium mixture.
heat
29

30. 2. Esters: reactions
30

31. 2. Esters: reactions
Show the esterification reaction that would produce
butyl propanoate.
pencast
31

32. 2. Esters: reactions
Esters can be synthesized starting from alcohols only.
An alcohol can be oxidized to an aldehyde, and further oxidized
to a carboxylic acid.
This carboxylic acid can undergo an esterification reaction with
another alcohol.
Name the required alcohols and show the necessary
reactions to produce
pentyl butanoate (apricots). pencast
octyl ethanoate (oranges).
32

33. 2. Esters: reactions
Hydrolysis (hydration) of esters, when it is acid-catalyzed,
is the reverse of the esterification reaction.
H2O
ester carboxylic acid alcohol
33

34. 2. Esters: reactions
Hydrolysis of esters, when it is base-catalyzed, is called
saponification.
ester carboxylic acid salt alcohol
34

35. 2. Esters: reactions
The carboxylic acid that forms when the ester breaks up
reacts immediately with the base, forming the
carboxylate anion, associated with the cation of the base.
35

36. 2. Esters: reactions
What are the products of the following reactions?
+ H2O
pencast
+ H2O
+ H2O
+ H2O
36

37. 2. Esters: saponification
(salts of carboxylic acids)
+ +
37

38. 2. Esters: saponification
A soap (carboxylic acid salt)
has a nonpolar end that dissolves in nonpolar fats and oils, and
a polar end that dissolves in water.
forms groups of soap molecules called micelles that dissolve in
water and are washed away.
38

39. 2. Esters: saponification
39

40. EXTRA CREDIT QUESTION
Radioactive isotopes of an element behave chemically in exactly the
same manner as the nonradioactive isotopes. As a result, they can be
used as tracers to investigate the details of chemical reactions. A
scientist is curious about the origin of the bridging oxygen atom in an
ester molecule. She has chosen to use the radioactive isotope 18O to
study the following reaction:
Design experiments using 18O that will demonstrate whether the oxygen
in the water molecule came from the –OH of the alcohol or the –OH of
the carboxylic acid.
Post your answer in the Journal for this module with tag = isotopes.
40

41. 3. Acid chlorides and acid anhydrides
Acid chlorides are carboxylic acid derivatives in which the
hydroxyl group, -OH, has been replaced by –Cl.
Naming
Name the corresponding carboxylic acid.
Replace the -oic acid ending with –oyl chloride.
41

42. 3. Acid chlorides and acid anhydrides
Examples
ethanoic acid ethanoyl chloride
benzoic acid benzoyl chloride
42

43. 3. Acid chlorides and acid anhydrides
Name the following acid chlorides.
pencast
Draw structures for the following acid chlorides.
heptanoyl chloride
2-hydroxypropanoyl chloride
43

44. 3. Acid chlorides and acid anhydrides
Preparation of acid chlorides
PCl3 or
+ PCl5 or + inorganic products
SOCl2
The reagents PCl3, PCl5, and SOCl2 are inorganic acid chlorides.
44

45. 3. Acid chlorides and acid anhydrides
PCl3, PCl5, and SOCl2 replace the hydroxyl group on the
acid with a chloride, by the following mechanism!
45

46. 3. Acid chlorides and acid anhydrides
Write an equation for the reaction of benzoic acid with
SOCl2 and name the organic product.
pencast
SOCl2
benzoyl chloride
46

47. 3. Acid chlorides and acid anhydrides
Acid anhydrides are two carboxylic acid molecules with a
water molecule removed.
+ H2O
47

48. 3. Acid chlorides and acid anhydrides
Acid anhydrides with identical acyl groups are symmetrical.
Symmetrical acid anhydrides are named after the acid from
which they are made, with the acid ending replaced with
anhydride.
The molecule above, made from two molecules of ethanoic acid, is
called ethanoic anhydride.
48

49. 3. Acid chlorides and acid anhydrides
Unsymmetrical anhydrides have two different acyl groups.
Unsymmetrical anhydrides are named using both parent
carboxylic acid names, in alphabetical order, followed by the
word anhydride.
The molecule above is called butanoic ethanoic anhydride.
49

50. 3. Acid chlorides and acid anhydrides
Name the following acid anhydrides.
pencast
50

51. 3. Acid chlorides and acid anhydrides
Acid anhydrides can be prepared from an acid chloride
and a carboxylate anion.
Direct reaction of the two parent carboxylic acids is usually not
possible.
acid chloride carboxylate anion acid anhydride
51

52. 3. Acid chlorides and acid anhydrides
Write equations for the synthesis of butanoic anhydride,
beginning with butanoic acid.
pencast
52

53. 3. Acid chlorides and acid anhydrides
Acid anhydrides react with water, if it is present, to
produce two carboxylic acids.
+ H2O
53

54. 3. Acid chlorides and acid anhydrides
What are the products of the hydrolysis of
ethanoic anhydride? pencast
ethanoic methanoic anhydride?
54

55. 3. Acid chlorides and acid anhydrides
An acid anhydride can also react with an alcohol, in a
reaction analogous to hydrolysis.
Hydrolysis: products are two carboxylic acids.
Reaction with alcohol: products are an ester and an acid.
55