1st year Organic Chem in Nursing-my group's powerpoint presentation. Enjoy! Not responsible for any error in information..it's been 3 years and I'm not sure if I corrected the information after we presented and were critiqued
1. Carboxylic Acids and Their
Derivatives
Lab Performed by 1Nur9-Grp 5
Elias, Jose Emmanuel D.
Esperanza, John Ruben A.
Flores, Norman Karl
Genilla, Jonathan L.
Manalo, Michelle C.
2. Carboxylic Acids
• INTRODUCTION
• Carboxylic acids are weak acids. They have sour or tart taste,
produce hydronium ions in water, and neutralizes base. Carboxylic
acid reacts with an alcohol to form an ester. In an ester, the –H of
the carboxylic acid is replaced by an alkyl group. Aspirin is an ester
as well as carboxylic acid. Amines and amides are organic
compounds that contain nitrogen. Many nitrogen containing
compounds are important to life as components of amino acids,
proteins and nucleic acid: DNA and RNA. Many amines that exhibit
strong physiological activity are used in medicine as decongestants,
anesthetics, and sedatives. Amides are derived from carboxylic
acids and amines. In biochemistry, the amide bond is called the
peptide bond, which links amino acids in proteins.
3. CARBOXYLIC ACIDS
• CARBOXYLIC ACID
• In carboxylic acids, the functional group is the carboxyl group,
which is combination of the carbonyl group and hydroxyl group.
• The carboxyl functional group maybe attached to an alkyl group or
an aromatic group.
•
O
•
‖
• —OH –COOH CO2H
C
•
• You encounter carboxylic acids when you use a vinegar salad
dressing, which is a solution of acetic acid and water, or experience
the sour taste of citric acid in grapefruit or lemon.
6. Results
Sample
Solubility in H2O
+ Na2CO3 →
Effervescence
+ HCl →
Formation of
precipitate
Acetic acid
Soluble
2 – 3 drops
No precipitate in
yellow solution
Triethylamine
Soluble
5 drops
Bubbly brown top
layer (precipitate)
with liquid bottom
layer
Benzoic acid
Insoluble
5 drops, still no
effervescence
White precipitate
on top of colorless
liquid
7. Explanations
Intermolecular bonding
Acetic acid
..
O
II . .
CH3 – C – . . +
OH
.. ..
O
H
H
Acetic acid is soluble in water due to its one – carbon
length and three hydrogen bonding possibilities.
•Carbonyl oxygen with hydrogen of water
•Hydroxyl oxygen with hydrogen of water
•Hydroxyl hydrogen with oxygen of water
8. Triethylamine
..
CH3 – N – CH3
I
CH3
.. ..
O
H
H
Triethylamine is slightly soluble in water due to the nitrogen
in the amine forming an H – bond with a hydrogen of water.
Primary and secondary amines have nitrogen (amine) to
hydrogen (water) bonding and hydrogen (amine) to oxygen
(water) bonding. But in triethylamine, a tertiary amine, only
the nitrogen (amine) to hydrogen (water) bonding is possible.
9. Benzoic acid
..
O
II ..
C – OH +
..
.. ..
O
H
H
Benzoic acid is insoluble in water for two reasons.
•The carboxyl group is bonded to the benzene
ring. Benzene is insoluble in water.
•There are seven carbons in the benzoic acid
molecule. Carboxylic acids with five or more
carbons are insoluble in water.
10. Chemical equations
Acetic acid
CH3COOH + H2O + Na2CO3 → CH3COONa + H2O + CO2↑
Bubbles of carbon dioxide were formed when sodium
bicarbonate was added to the acetic acid solution. And, a
carboxylic acid salt (sodium acetate) was formed (and
dissolved in water).
CH3COONa + H2O + HCl → CH3COOH + NaCl + H2O
No precipitate was formed after the addition of
hydrochloric acid to the sodium acetate solution. Since
the products (acetic acid and sodium chloride) were both
dissolved in water, no precipitate was formed.
11. Triethylamine
1. (CH3CH2)3N + H2O + Na2CO3 →
(CH3CH2)3N + Na2CO3 + H2O + CO2↑
2. (CH3CH2)3N + Na2CO3 + H2O + HCl →
(CH3CH2)3N + H2O + NaCl + CO2↑
The triethylamine remained untouched after the addition of sodium
bicarbonate. Instead, the sodium bicarbonate decomposed into
sodium carbonate, water, and carbon dioxide (effervescence) (eq. 1).
Then, the hydrochloric acid was added, yielding sodium chloride and
carbonic acid. Carbonic acid eventually broke down into water and
carbon dioxide, thus producing a second batch of effervescence.
Once again, the triethylamine was untouched after the addition of
hydrochloric acid (eq. 2).
12. 1. C6H5COOH + H20 + NaHCO3 → no reaction
2. C6H5COOH + H20 + NaHCO3 + HCL →
C6H5COOH + NaCl + H2O
• No bubbles were formed in the benzoic acid
solution after the addition of sodium
bicarbonate. In fact, benzoic acid is insoluble in
water at room temperature, but soluble in water
at boiling point (eq. 1). The benzoic acid crystals
were seen floating on water surface, even after
the addition of hydrochloric acid. Instead, the
sodium bicarbonate reacted with hydrochloric
acid, producing sodium chloride and carbonic
acid, which later broke down into carbon dioxide
and more water (eq. 2).
13. Benzoic acid
C6H5COOH + H2O + Na2CO3 → no reaction
There was no bubble formation after adding sodium
bicarbonate since benzoic acid is insoluble in water at
room temperature (but soluble at water’s boiling point).
C6H5COOH + H2O + Na2CO3 + HCl → C6H5COOH + H2O + NaCl +
CO2↑
The white “precipitate” in this chemical reaction (after the
addition of sodium bicarbonate and hydrochloric acid)
was the insoluble benzoic acid. The only reaction that
occurred here was between the added compounds
(sodium bicarbonate and hydrochloric acid), which
formed sodium chloride, more water, and carbon dioxide
effervescence.
14. Study Question 1 for Solubility
• Account for the difference in solubility: the
carboxylic acids and amines in 1) water and 2)
sodium bicarbonate and 3) hydrochloric acid.
• Intermolecular bonding and solubility in
water
• Acetic acid is soluble in water because of the
following reasons, besides from its polarity
(the carboxyl group provides the acid’s
polarity).
15. Study Question 1 for Solubility
• It has only two carbons. Aldehydes and ketones
with at most four carbons are infinitely soluble in
water.
• There are three hydrogen bonding possibilities in
acetic acid.
– Carbonyl oxygen H – bonds with hydrogen of water.
– Hydroxyl oxygen H – bonds with hydrogen of water.
– Hydroxyl hydrogen H – bonds with oxygen of water.
16. Study Question 1 for Solubility
• Trimethylamine is partly soluble in water due to
the nitrogen in the amine molecule forms an H –
bond with hydrogen of a water molecule. Primary
and secondary amines have nitrogen (amine) to
hydrogen (water) bonding, as well as hydrogen
directly bonded to nitrogen (amine) to oxygen
(water) bonding. But in triethylamine, a tertiary
amine, only the nitrogen (amine) to hydrogen
(water) bonding is possible, because no hydrogen
is directly bonded to the nitrogen.
17. Study Question 1 for Solubility
• Benzoic acid is insoluble in water at room
temperature (but soluble in hot water) for two
reasons.
• The carboxyl group is bonded to a benzene
ring. Benzene is nonpolar and insoluble in
water.
• There are seven carbons in the benzoic acid,
six in the benzene ring plus one carboxyl
carbon.
18. Study Question 1 for Solubility
•
•
•
•
Chemical reactions and equations
CH3COOH + H2O + Na2CO3 → CH3COONa + H2O + CO2↑
CH3COONa + H2O + HCl → CH3COOH + NaCl + H2O
Addition of sodium bicarbonate (Na2CO3) to the acetic
acid solution produced effervescence, carbon dioxide
bubbles. Also, a carboxylic acid salt was produced,
sodium acetate (eq. 1). Later, hydrochloric acid was
added to the sodium acetate solution. This reaction
yielded acetic acid and sodium chloride; both products
are soluble in water. Thus, no precipitate was formed
after adding hydrochloric acid (eq. 2).
19. Study Question 1 for Solubility
• (CH3CH2)3N + H2O + NaHCO3 → (CH3CH2)3N + Na2CO3 + H2O + CO2↑
• (CH3CH2)3N + Na2CO3 + H2O + HCl → (CH3CH2)3N + H2O + NaCl +
CO2↑
• The triethylamine remained untouched after the addition of sodium
bicarbonate. Instead, the sodium bicarbonate decomposed into
sodium carbonate, water, and carbon dioxide (effervescence) (eq.
1). Then, the hydrochloric acid was added, yielding sodium chloride
and carbonic acid. Carbonic acid eventually broke down into water
and carbon dioxide, thus producing a second batch of
effervescence. Once again, the triethylamine was untouched after
the addition of hydrochloric acid (eq. 2).
20. Study Question 1 for Solubility
• C6H5COOH + H2O + NaHCO3 → no reaction
• C6H5COOH + H2O + NaHCO3 + HCl → C6H5COOH + NaCl +
H2O
• No bubbles were formed in the benzoic acid solution after
the addition of sodium bicarbonate. In fact, benzoic acid is
insoluble in water at room temperature, but soluble in
water in hot water (eq. 1). The benzoic acid crystals were
seen floating on water surface, even after the addition of
hydrochloric acid. Instead, the sodium bicarbonate reacted
with hydrochloric acid, producing sodium chloride and
carbonic acid, which later broke down into carbon dioxide
and more water (eq. 2).
22. AMINES
• Amines are considered as derivatives of
ammonia (NH3) in which one or more
hydrogen atoms is replaced with alkyl or
aromatic groups. For example, in
methylamine, a methyl group replaces one
hydrogen atoms in ammonia. The bonding of
two methyl groups gives dimethylamine, and
the three methyl groups in trimethylamine
replace all the hydrogen atoms in ammonia.
23. CLASSIFICATION OF AMINES
• Amines are classified the same way as
alcohols by counting the number of carbon
atoms directly bonded to a nitrogen atom. In a
primary amine, one carbon is bonded to a
nitrogen atom. In a secondary amine, two
carbons are bonded to the nitrogen atom, and
a tertiary amine has three carbon atoms
bonded to the nitrogen.
25. PROPERTIES OF AMINES
• Amines have higher boiling points than alkanes of
similar mass, but lower than the alcohols.
• Because amines contain a polar N—H bond, they form
hydrogen bonds. However, nitrogen is not as
electronegative as oxygen, which makes the hydrogen
bonds in amines weaker. The —NH2 in primary amines
can form more hydrogen bonds, which gives them
higher boiling points than the secondary amines of the
same mass. It is not possible for tertiary amines to
hydrogen bond with each other(no N—H bonds), which
makes their boiling points much lower and similar to
those of alkanes.
26. PROPERTIES OF AMINES
• Amines are stonger proton acceptors than oxygencontaining organic compounds such as alcohols and
ethers; that is, they are stronger bases than these
compounds. A 0.1 M aqueous solution of
methylamine has a pH of 11.8 and a 0.1 M of
aqueous solution of aniline has a pH of 8.6. these
solutions are sufficiently basic to turn red litmus
paper blue. Carboxylic acid salts are the only other
type of organic compound sufficiently basic to turn
red litmus paper red.
27. AMIDES
• Amides are derivatives of carboxylic acid in
which an amino group replaces the hydroxyl
group
28. AMIDATION
• An amide is produced in a reaction called
amidation, in which a carboxylic acid reacts
with ammonia or a primary or secondary
amine. A molecule of water is eliminated, and
the fragments of the carboxylic acid and
amine molecules join to form the amide,
much like the formation of ester. Because a
hydrogen atom must be lost from the amines,
only primary and secondary amines undergo
amidation.
29. ACETAMIDE
• -unlike other water-insoluble organic substances, saponification of
an amide releases ammonia which is very distinct for its pungent
and urine like smell.
• *red litmus paper turned blue on ACETAMIDE due to the presence
of ammonia(weak base)
• -nitrogen atom in the molecule has a lone pair making it a proton
acceptor
30. BASICITY OF AMINES
• Because amines acts as weak bases by
accepting protons from water and producing
hydroxide ions, their aqueous solutions are
basic.
31. PROPERTIES OF AMINES
• Most of the K value for amines are less than
10^-3, which means that the equilibrium
favored the undissociated amine molecules.
Aqueous solutions of amines have basic pH
values and turn litmus paper blue.
32. HYDROLYSIS OF AMIDES
• The most important reaction of amides is
hydrolysis. In amide hydrolysis, the bond
between the carbonyl carbon atom and the
nitrogen is broken, and free acid and free
amine are produced. Amide hydrolysis is
catalyzed by acids, bases, or certain enzymes;
sustained heating is also often required.
33. HYDROLYSIS OF AMIDES
• Acidic or basic hydrolysis conditions have an
effect on the products. Acidic conditions
convert the product amine to amine salt. Basic
conditions convert the product carboxylic acid
to a carbxylic acid salt.
• (PICTURE COURTESY OF BOOK page 715)
34. HYDROLYSIS OF AMIDES
• Amide hydrolisis under basic conditions is also
called amide saponification, just as ester
hydrolysis under basic conditions is called
ester saponification.
• (PICTURE COURTESY OF BOOK PAGGE 715)
35. HYDROLYSIS OF AMIDES
• Amide bonds are formed by the elimination of
water. The reverse reaction called hydrolysis
occurs when water is added back to the amide
bond to split the molecule. When an acid is
used, the hydrolysis products of an amide are
the carboxylic acid and the ammonium salt. In
base hydrolysis, the amide produces the salt
of carboxylic acid and ammonia or amine.
36. HYDROLYSIS OF AMIDES
• Of the various acid derivatives, amides are the least
reactive toward nucleophilic attack, because the unshared
electron pair on the nitrogen is delocalized to the carbonyl
carbon through resonance.
• Thus, unlike most acyl halides or anhydrides, amides must
be heated to boiling with aqueous acid or base in order to
hydrolyze them. For a primary amide, the product will be
ammonium ion and the acid (for acidic hydrolysis) or
ammonia and carboxylate ion (for alkaline hydrolysis). The
reaction mechanisms are similar to those for the hydrolysis
of other acid derivatives.
37. SAPONIFICATION
• Procedure:
• 1. Prepare 2 clean and dry text tubes. Place
1.0 triethylamine in tube 1, and pinch-amount
of acetamide in tube 2. add 1.0 of dilute 6N
NaOH solution to each tube and mix
thoroughly.
• 2. Heat all 2 tubes in a boiling water bath for
two minutes.
40. ESTERS
• An ester is similar to a carboxylic acid, except
that the oxygen of the carboxyl group is
attached to a carbon and not to hydrogen. In
ester, the –H of the carboxylic acid is replaced
by an O-akyl (alkoxy) group. Fats known as
Triglycerides are esters of glycerol and fatty
acids, which are long-chain carboxylic acids.
Esters produce the pleasant aromas and
flavors of many fruits such as bananas,
strawberries, and oranges.
41. Introduction
• An ester is a carboxylic acid derivative in
which the –OH portion of the carbonyl group
has been replaced with an –OR group.
• The ester functional group is
O
C
O
R
42. Study Question 2: Saponification
• The principle used in the saponification is
hydrolysis. In amide hydrolysis, the bond
between the carbonyl atom and the nitrogen
is broken, and free acid and free amide are
produced. Amide hydrolysis is catalyzed by
acids, bases, or certain enzymes; also
sustained heating is often required.
43. Study Question 2: Saponification
• Amide hydrolysis:
• Hydrolysis under Acidic Conditions
• Hydrolysis under Alkaline Conditions
• Acidic or basic hydrolysis conditions have an
effect on the products. Acidic conditions convert
the product amine to amine salt. Basic conditions
convert the product carboxylic acid to carboxylic
acid salt.
44. Study Question 2: Saponification
• Acidic or basic hydrolysis conditions have an effect on the
products. Acidic conditions convert the product amine to
amine salt. Basic conditions convert the product carboxylic
acid to carboxylic acid salt.
•
Saponification helps differentiate the amides from the
rest of other water-insoluble compounds because the test
reacts on carbonyl atom and nitrogen when carbon is
present in amides.
•
Amides are capable of participating to H-bonding with
water and other priotic solvents; the atom can accept
hydrogen bonds from water and the N-H hydrogen atoms
can donate H-bonds. As a result of interactions such as
these, the water solubility of amides is greater than that of
other hydrocarbons.
46. PROPERTIES OF ESTERS
– Boiling point: lower than alcohols and carboxylic
acid.
– Cannot form hydrogen bonds because they do not
have a hydrogen atom bonded to an oxygen atom.
– Solubility: rapidly decrease with increasing carbon
chain length
– Most have pleasant odors such as raspberry,
banana, pear, apple and pineapple.
47. Preparation of Esters
• General formula:
Esters can be prepared through a process called
“Esterification”.
49. ESTERIFICATION
• In a reaction called esterification, a
carboxylic acid reacts with an
alcohol when heated in the
presence of an acid catalyst. In the
reaction, water is produced from
the –OH removed from the
carboxylic acid and an –H lost by
the alcohol.
50. Lab Experiment-Esterification
• Procedure:
• 1. Prepare two clean and dry test tubes. To tube
1, place pinch-amount of salicylic acid and 2.0
ml of methanol. To tube 2, place 2.0 ml of
95% ethanol and 1.0 ml of glacial acetic acid.
Add slowly to both tubes five drops of conc.
Sulfuric acid. (CAUTION: concentrated
sulfuric acid is very corrosive. See first aid
measures in case of accident.) Mix the
contents of both tubes thoroughly.
51. Lab Experiment- Esterification
• 2. Heat both tubes in a boiling water bath
until the either the odor of the alcohol or
the acid used is no longer obvious. Prepare
two evaporating dishes. In each dish, place
5.0 ml hot water. Pour the contents of test
tubes 1 and 2 separately in the
evaporating dish. Immediately note the
odor of each sample and record your
observations.
54. • Both samples yield esters into which the –H of
the carboxylic acids (Acetic Acid and Salicylic
Acid) was replaced by an alkyl group.
• In the experiment the –OH group is lost from
the carboxylic acid, a –H atom is lost from the
alcohol and water is formed as a by-product.
The results of this reaction was the
substitution of an –OR group of the alcohol
and for the –OH group of the acid.
55. Study Question 3
• Aside from amides and carboxylate esters,
what are the other kinds of esters? Give their
equations.
• Methyl Ethanoate
• Ethyl Ethanoate
• Methyl Methanoate
56. • Ethyl Ethanoate
Study Question 3
• Methyl Methanoate
• Ethyl Methanoate
These are four of the most common kinds of esters.
57. Study Question 4
• In the formation of esters, why is there a need to
add a small amount of concentrated sulfuric acid?
•
Formation of esters may be achieved through
“esterification”. It is a reaction of a carboxylic acid
and with an alcohol (or phenol) to produce an
ester. In order for esterification to be achieved a
strong catalyst is needed. The Sulfuric Acid
(H2SO4) serves as a catalyst in the process of
esterification which helps increase the chemical
reaction.
60. Uses
Aspirin is one of the most widely
used drugs in modern society. It is
most frequently used to treat mild to
moderate pain or to reduce fever.
Because of its anti-inflammatory
action, aspirin is prescribed to
individuals who suffer from joint
inflammation conditions such as
rheumatoid
arthritis
and
osteoarthritis.
63. Acetylsalicylic Acid
(C6H4OCOCH3COOH) is the ubiquitous
pain reliever known as aspirin.
Chemically, aspirin is both an
aromatic acid and an ester;
analgesic properties not with
standing, the compound is an
excellent showcase for at least two
or three principles of organic
chemistry.
64. Salicylic Acid
(C6H4OHCOOH; aspirin's parent
compound) and sodium salicylate
(C6H4OHCOONa) are useful for detecting
iron compounds; they form colored
complexes with the Fe3+ ion. They can also
be used in several organic chemistry
experiments which illustrate important
principles.
66. Acid Hydrolysis
“Acid Hydrolysis is the breaking of
the carbon-oxygen single bond
between the “alcohol” part and the
“acid” part. It is also the most
important reaction of esters.”
72. Base Hydrolysis
“Saponification reaction under basic
conditions, hydrolysis of an organic
compound in which the product is a
carboxylic acid salt. All of the
following go through saponification:
esters, amides, fats and oils.”
73. Ester Saponification
“A reaction between the ester and a base to
produce a carboxylic acid salt and alcohol. In
this reaction, all carboxylic acid products are
converted to its salt form due to the
conditions of the basic reaction.”
74. Lab Report-Hydrolysis of Esters
• Acetate Ion (CH3COO-)
• Basic Ferric Acetate Test: Dissolve a small
quantity of CH3COONa in 3 drops of distilled
water. Add 3 drops of 0.5 M FeCl3 solution. If
no color change is observed, add one drop of 6
M nitric acid. Record all observations on the
data sheet.
75. Lab Report-Hydrolysis of Esters
• Figure 1. Structure of acetylsalicylic acid.
• Aspirin is one of the most widely used drugs in modern society. It is most
frequently used to treat mild to moderate pain or to reduce fever. Because
of its anti-inflammatory action, aspirin is prescribed to individuals who
suffer from joint inflammation conditions such as rheumatoid arthritis and
osteoarthritis.
• Figure 2. Hydrolysis of acetylsalicylic acid to acetic acid and salicylic acid.
76. Lab Report-Hydrolysis of Esters
PROCEDURE:
D. Hydrolysis of an Ester
Dilute 5.0 ml of 6N sodium hydroxide with an equal volume of water in a
hard glass test tube. Add 5.0 g of acetylsalicylic acid and heat in a boiling
water bath for five minutes. Cool to room temperature and then acidify
the mixture with 6N hydrochloric acid until a precipitate is formed. Filter.
1. Basic Ferric Acetate Test
To 1.0 ml of the filtrate obtained from hydrolysis, add 6N sodium
hydroxide until the solution is slightly alkaline to litmus paper. Add
ferric chloride dropwise to the solution until a change is noted.
Record your observations.
2. Ferric Chloride Test
Mix a pinch of the residue obtained from hydrolysis with 2.0 ml water. Add
three drops of ferric chloride and note what happens. Record your
observation.
77. Summary of the Hydrolysis of Ester
"The hydrolysis of Ester (ASA/Aspirin) will yield acetic
acid and salicylic acid. Acetic acid, together with the
filtrate, will react to the ferric ion. Acetic acid will be
neutralized and will become Acetate so that Sodium
Hydroxide will be the one reduced and not Acetic
Acid. Acetate will then react with Ferric Chloride,
producing Ferric Acetate which has the visible result
present in the experiment.(reddish brown color)."
79. Basic Ferric Acetate Test versus Ferric
Chloride Test
• OBJECTIVE
• "The primary objective of Basic Ferric Acetate
Test is to test for any presence of ferric ions
with the use of Ferrous Acetate and the
filtrate. On the other hand, Ferric Chloride
Test is used to test for phenols as residue is
added."
80. RESULT OF BASIC FERRIC ACETATE TEST
• VISIBLE RESULT
• "An aqueous solution of Basic Ferric Acetate
will yield a reddish brown liquid. The Acetate
from the neutralized Acetic Acid will react
with the Ferric Chloride, producing Ferric
Acetate which is the one responsible for the
visible result in the solution."
81. Ferric acetate is the coordination
compound more commonly known
as "basic iron acetate". With the
formula [Fe3O(OAc)6(H2O)3]OAc
(OAc is CH3CO2-), it is a salt,
composed of the cation [Fe3(μ3O)(OAc)6(H2O)3]+ and an acetate
anion. The formation of the redbrown complex has long been
used as a test for ferric ions.
83. The ferric chloride test is used to determine the
presence or absence of phenols in a given
sample. Enols give positive results as well. The
bromine test is useful to confirm the result.
Phenols form a complex with Fe(III), which is
intensely colored. This is the basis for the
test.The sample is dissolved in water, or a
mixture of water and ethanol, and a few drops
of dilute ferric chloride solution is added. The
formation of a red, blue, green, or purple
coloration indicates the presence of phenols.
Where the sample is insoluble in water, it may
be dissolved in dichloromethane with a small
amount of pyridine.
84. Lab Report-Introduction to the
Ferric Acetate Test
• Acetylsalicylic acid (C6H4OCOCH3COOH) is the ubiquitous pain reliever
known as aspirin. Chemically, aspirin is both an aromatic acid and an
ester; analgesic properties notwithstanding, the compound is an excellent
showcase for at least two or three principles of organic chemistry.
• Salicylic acid (C6H4OHCOOH; aspirin's parent compound) and sodium
salicylate (C6H4OHCOONa) are useful for detecting iron compounds; they
form colored complexes with the Fe3+ ion. They can also be used in several
organic chemistry experiments which illustrate important principles.
• For convenience we may abbreviate acetic acid as HOAc or AcOH. This
refers to an acetate group ("OAc"; Figure 1) with a hydrogen ("H"). Acetic
acid loses an H+ when it ionizes to acetate, which is then abbreviated as
OAc-.
85. Lab Report-Introduction to the
Ferric Acetate Test
• Because the shorthand system becomes
ambiguous with more complex molecules,
we'll refer to salicylic acid as "SA" and
acetylsalicylic acid as "ASA". (Consider that
HOSal could be salicylic acid, if we assume the
dissociable H+ comes from the carboxylic acid
group.)
86. Basic Ferric Acetate Test
• Ferric acetate is the coordination compound more commonly known as
"basic iron acetate". With the formula [Fe3O(OAc)6(H2O)3]OAc (OAc is
CH3CO2-), it is a salt, composed of the cation [Fe3(μ3-O)(OAc)6(H2O)3]+
and an acetate anion. The formation of the red-brown complex has long
been used as a test for ferric ions.
•
• Figure 3. Reddish Brown Solution of Basic Ferric Acetate Test
• Laboratory Observation: The solution turned reddish brown in color.
87. Basic Ferric Acetate Test
• Q: In the basic ferric acetate test, why is it important
that the solution be kept neutral? What would
happen if there is an excess of acid or alkali?
• A: Acetate would either be oxidized or reduced.
88. Ferric Chloride Test
• The ferric chloride test is used to determine the presence or
absence of phenols in a given sample. Enols give positive
results as well. The bromine test is useful to confirm the result.
Phenols form a complex with Fe(III), which is intensely colored.
This is the basis for the test.The sample is dissolved in water,
or a mixture of water and ethanol, and a few drops of dilute
ferric chloride solution is added. The formation of a red, blue,
green, or purple coloration indicates the presence of phenols.
Where the sample is insoluble in water, it may be dissolved in
dichloromethane with a small amount of pyridine.
89. Ferric Chloride Test
Figure 4. Purple Solution of Ferric Chloride Test
-----------------------------------------------------------------------------------------------Laboratory Observation: The solution turns purple in color.
90. Study Question 5
Q: After alkaline hydrolysis of acetylsalicyclic acid and
acidification, what products (filtrate and residue)
are formed? Write the equations involved and
name the corresponding products.
A: The hydrolysis of acetylsalicyclic acid aspirin will
yield acetic acid (residue) and salicylic acid (filtrate).
91. Study Question 6
Q: What tests proved the identity of the products (filtrate and
residue). Give all equations involved and the formulas
responsible for the visible results.
A: The Ferric Chloride Test proved the identity of the products,
acetic acid and salicylic acid. The Ferric Chloride test showed
the presence of the phenol group –OH both the residue and
the filtrate which proved that the presence that both are
carboxylic acids.
O
Cl
||
|
CH3-C-OH + H2O+ FeCl3 -> FeO(OH) + CH3-C-Cl
|
Cl
Salicylic Acid + FeCl3 -> Iron (III) Salicylate and hydrochloric acid
+ FeCl3 -> Fe(C7H5O3)3 (aq) + 3HCl (aq)
3 C7H6O3 (aq)
93. Benzoic Acid
Introduction:
• Benzoic acid is the simplest aromatic
carboxylic acid. Its chemical formula is
C7H6O2 (or C6H5COOH).
• Its structure is of a benzene ring (6-sided ring)
and has the following attachment to a carbon
on its ring: a carbonyl group and a hydroxyl
group.
94. Physical and Chemical Properties of
Benzoic Acid
It’s a colorless, crystalline solid. Its melting point is at
122°C and its boiling point is 249°C.
• Solubility:
• Benzoic acid is soluble in hot water but in room
temperature water (25°C), its solubility is 0.34 g/100
ml, which means it is insoluble.
• It is soluble in ethanol (2.58M), methanol (2.91M).
•
• Chemical Properties
• Benzoic acid: pka = 4.21
95. Preparation of Benzoic Acid
Uses of Benzoic Acid
Benzoic Acid and its salts are used as
food preservatives. One of the salt
derivatives is the carboxylic acid salt,
benzoate.
96. Two possible reactions
• From the lab experiment performed, either
one of two reactions can occur:
• The production of a benzamide (if water used
was hot enough) or
• The production of a carboxylic acid salt, a
benzoate
• To coincide with my lab result, I will discuss
the production of a benzoate and thus will
proceed to discuss Carboxylic Acid Salts,
specifically enzoic Acid.
97. BENZOIC ACID
Introduction
• Benzoic acid is a weak acid, the simplest
aromatic carboxylic acid. Its chemical formula
is C7H6O2 (or C6H5COOH). Its structure is of a
benzene ring and has the following
attachment to a carbon on its ring: a carbonyl
group and a hydroxyl group.
98. BENZOIC ACID-PHYSICAL AND
CHEMICAL PROPERTIES
Physical Properties of Benzoic Acid
It’s a colorless, crystalline solid. Its melting point is at 122ºC and its boiling point
is 249ºC.
Solubility:
Benzoic acid is soluble in hot water but in room temperature water (25ºC), its
solubility is 0.34 g/100 ml, which means it is basically insoluble or only slightly
soluble in room temperature water. It is soluble in THF (3.37M), ethanol (2.58M),
methanol (2.91M).
Chemical Properties
Benzoic acid: pka = 4.21
99. BENZOIC ACID
• Preparation of Benzoic Acid
• Commercially, Benzoic acid is produced by the
partial oxidation of toluene with oxygen with
one the following catalysts: manganese
naphthenate or cobalt.
100. LAB EXPERIMENT- BACKGROUND
• From the lab experiment performed, either
one of two reactions could have occurred if
the right conditions were maintained:
• The production of a benzamide (100°C water
used) and a dehydrating agent was used.
• The production of a carboxylic acid salt, a
benzoate (if the water did not maintain
100°C).
101. LAB EXPERIMENT-BACKGROUND
As the water was not kept hot enough to
produce an amide, the resulting reaction
produced a benzoate and therefore, I will
proceed only in the discussion of carboxylic
acid salts and the “Test for Benzoic Acid” lab
experiment.
102. CARBOXYLIC ACID SALTS
• Carboxylic Acid Salt
• A carboxylic acid salt is an ionic compound in
which the negative ion is a carboxylate ion.
- Exploring Organic and Biological
Chemistry
• Carboxylic acid salts are produced from the
neutralization reaction between a carboxylic
acid and a strong base.
103. LAB REPORT-TEST FOR BENZOIC ACID
•
Lab Report: Test for Benzoic Acid
Objective:
To test for an aromatic acid, in this lab, it is a test for the presence of a benzoic acid
Reagents used:
Benzoic acid
Ammonium Hydroxide (6N NaOH)
Ferric Chloride [Iron (III) Chloride]
•
Materials/Equipment used:
Water bath (hot water)
One test tube
Graduated cylinder
Litmus paper
104. Reagents used in Lab experiment
Benzoic Acid
O
|| ..
C – OH
Ammonium Hydroxide
Iron (III) Chloride
Ferric (III) Chloride
|
NH4 OH - a Bronsted-Lowry Base
NH3
+ H20 => NH4+ + OHAmmonia Water Ammonium Hydroxide ion
(Base H+ (Acid H+ ion
(basic solution)
Acceptor) Donor)
105. LAB REPORT-TEST FOR BENZOIC ACID
Procedure:
1) Take 1 test tube and add water (6-7 ml)
2) Heat in a hot water bath and after heating, make
sure there is 5ml of water left for the procedure
3) Dissolve a “mongo-grain” amount of Benzoic Acid
in the 5ml of hot H20
4) Add 6N NH4OH until the solution is neutral or
slightly alkaline (test with litmus paper).
5) If it is alkaline, warm until solution is neutral.
6) Add 6 gtts of FeCl3 and note what is formed.
106. LAB REPORT-TEST FOR BENZOIC ACID
• Reaction: A benzoate is formed from a
reaction between the weak acid, Benzoic
Acid, and the weak base, Ammonium
Hydroxide (Brönsted-Lowry Base) and the
FeCl3 is used to detect if there is an aromatic
acid. The positive test for benzoic acid using
FeCl3 will be a precipitate of an orange or tan
color.
107. LAB REPORT-TEST FOR BENZOIC ACID
• Benzoic Acid + Ammonium hydroxide →
Ammonium benzoate + Iron (III) Chloride
+
→3
Cl
→
→ + H2O + FeCl3
+ Fe(OH)3 ↓ + H2O
FERRIC (III) HYDROXIDE IS THE COMPOUND RESPONSIBLE
FOR THE ORANGE PRECIPITATE
108. LAB REPORT-TEST FOR BENZOIC ACID
• Benzoic acid is not soluble in water as it has a benzene ring and therefore
does not have free protons (hydrogens) to donate as part of a hydrogen
bond. In order to neutralize benzoic acid, ammonium hydroxide is used.
The carboxylic acid salts are solids at room temperature and have high
melting points. Because they are ionic compounds, carboxylic acid salts of
the alkali metals (Li+, Na+, and K+) and NH4+ are usually soluble in water.
•
• The Neutralization reaction between the carboxylic acid, Benzoic acid and
the base, Ammonium hydroxide produces a Carboxylic Acid salt,
Ammonium benzoate. The Iron (III) Chloride was used to produce a
reaction showing the presence of an aromatic acid.
•
• RESULT: My lab experiment yielded a rusty orange or tan precipitate in
turbid solution which proves a positive test for benzoic acid.
•
•
111. Amides
• Amides are derivatives of carboxylic acid in which the
carboxyl –OH group is replaced with an amino group or
a substituted amino group ( NH2, NH, N).
Primary Amide
Secondary Amide
Tertiary Amide
Unsubstituted
Monosubstituted
Disubstituted amides
O
||
R-C-NH2
Two hydrogen atoms bond to
the amide nitrogen atom
O
O
||
R-C-NH-R’
An alkyl (or aryl) group and a
hydrogen atom are bonded to
the amide nitrogen atom
O
O
||
R-C-N-R’
|
R
Two alkyl (or aryl) groups and
no hydrogen atoms are bonded
to the amide nitrogen atoms.
112. Physical Properties of Amides
• Amides have a lone pair (nonbonding pair) of
electrons which is not vailable for bonding
with H+ ions, as Amines do, thus amides do
not exhibit the same basic properties of
amines.
113. Benzamide
• A benzamide is a secondary (2°)
amide produced from the
Amidification Reaction (a
Condensation reaction) of a benzoic
acid and a primary amine, or in the
case of the lab, an ammonia.
114. Carboxylic Acid Salt
• A carboxylic acid salt is an ionic compound in
which the negative ion is a carboxylate ion.
- Exploring Organic and Biological
Chemistry
• Carboxylic acid salts are produced from the
neutralization synthesis reaction between a
carboxylic acid and a strong base.
115. Lab Report-Test for Benzoic Acid-Part E
Objective:
To test for an aromatic acid, in this lab, it is a test for the presence of a
benzoic acid
Reagents used:
• Benzoic acid
• Ammonium Hydroxide (6N NaOH)
• Iron (III) Chloride
Materials/Equipment used:
• Water bath (hot water)
• One test tube
• Graduated cylinder
• Litmus paper
116. Lab Experiment-Test for Benzoic Acid
Procedure:
1. Take 1 test tube and add water (6-7 ml)
2. Heat in a hot water bath making sure there is 5ml of water left for
the procedure
3. Dissolve a “mongo-grain” amount of Benzoic Acid in the 5ml of
hot H20
4. Add 6N NH4OH until the solution is neutral or slightly alkaline (test
with litmus paper).
5. If it is alkaline, warm until solution is neutral.
6. Add 6 gtts of FeCl3 and note what is formed.
In the laboratory iron(III) chloride is commonly employed as a
Lewis acid for catalysing reactions such as chlorination of
aromatic compounds and Friedel-Crafts reaction of aromatics.
117. Two different products can be derived from this lab
experiment depending on the temperature of the
water used. For the purpose of this report, I will
discuss both results.
If hot water (100 °C) water was used during the reaction between the
carboxylic acid and an amine, then an amide will be the product.
Product: Ammonium Benzamide (hot water-100°C)
If room temperature water (25°C) water was used during the reaction,
then this will be an acid-base reaction producing a carboxylic acid
salt.
• Two different products can be produced depending on if the water
used was hot or not:
• Product: Ammonium Benzoate (warm water)
118. Reactions
• Reaction 1: A benzamide is formed from the
reaction between the Benzoic acid and the
Ammonium Hydroxide and the Iron (III)
Chloride [FeCl3) is used as a catalyzing agent.
catalyzing agent.
Hot H2O (100ºC) and FeCl3
-C-OH
+
NH4OH →
-NH2
O
||
C- NH2
+
+ FeCl3 →
+ FeO(OH) ↓ + H2O
119. Reactions
• Reaction 2: A benzoate is formed from a reaction
between Benzoic Acid and Ammonium Hydroxide
(Bronsted-Lowry Base) and the FeCl3 is used to
detect if there is an aromatic acid.
• Ferric Chloride Test: For presence of aromatic acid.
warm H2O
-C-OH
NH4OH →
+
C7H9NO2
Benzoic Acid + Ammonium hydroxide → Ammonium benzoate
+
→
+ H2O
120. Result of Lab Experiment
Yield: A rusty orange precipitate in turbid
solution.