9.

1 EXECISE
SECTION A
For each question there are four possible answers, A, B, C and D. choose the one you
consider to be correct.
1. Carboxylic acids have the functional group __________.
A. carbonyl
B. carboxyl
C. carbonate
D. alkyl

2. Which of the following is not a carboxylic acid derivative?

A. Methyl propanoate
B. Ethanamide
C. Ethanoyl chloride
D. Propanone
3. Consider the organic compound;

Which functional group is present in this compound?

A. Amide
B. Anhydride
C. Ester
D. Carboxyl
4. Carboxylic acids are soluble in water due to their ability to form __________ with
water.
A. hydrogen bonds
B. covalent bonds
C. ionic bonds
D. metallic bonds
5. Primary alcohols and ___________ can be oxidised to carboxylic acids in acidic
solution by potassium dichromate (VI).
A. ketones
B. esters
C. amides
D. aldehydes
6. The base hydrolysis of an ester is called ____________.
A. esterification
B. saponification
C. hydrolysis
D. neutralization
7. Esterification is the reaction of a (n) _________ with an alcohol.
A. amide
B. carboxylic acid
C. ester
D. amine
8. Vinegar contains a carboxylic acid known as __________.
A. citric acid
B. ethanoic acid
C. nitric acid
D. methanoic acid
9. Chlorine atoms are regarded as electron ____________.
A. acceptors
B. donators
C. withdrawing group
D. sharing group
10. Acyl chlorides are made by reacting carboxylic acids with __________.
A. PCl5
B. SOCl2
C. PCl3
D. All of them
11. CH 3 CH 2 COCl is structural formula for __________.
A. ethanoyl chloride
B. propanoyl chloride
C. propanoic acid
D. chloro propanoate
12. Carboxylic acids react with __________ to liberate carbon dioxide gas.
A. sodium carbonate
B. sodium hydroxide
C. sulphuric acid
D. alcohols
13. Carboxylic acids undergo reactions to produce derivatives of the acid. Which of the
following is not a carboxylic derivative?
A. Ethyl ethanamide
B. Butyl chloride
C. propyl ethanoate
D. methyl propanal

14. If benzoic acid undergoes a chemical reaction with ethanol in the presence of
concentrated sulphuric acid, ethyl benzoate and water are produced. The reaction is
called __________.
A. esterification
B. acid hydrolysis
C. saponification
D. base hydrolysis
15. Fatty acids are carboxylic acids consisting of a long hydrocarbon chain at one end
and a __________ at the other end.
A. carboxyl group
B. carbonyl group
C. hydroxyl group
D. aryl group
16. consider the anhydride;

What name is given to this compound?

A. Propanoic ethanoic anhydride
B. Ethanoic propanoic anhydride
C. Ethanoic anhydride
D. Methanoic propanoic
17. Food industry uses many organic acids like citric acid and lactic acid for the
production of __________.
A. soft drinks
B. cheese
C. milk
D. all of them
18. When a triglyceride is hydrolysed in a basic medium, the products of the reaction are
__________ and the salts of the respective fatty acids.
A. Carboxylic acid
B. Triglycerol
C. Glycerol
D. Soap
19. Consider the acid hydrolysis of ethane nitrile under reflux conditions;
CH 3 CN + 2 H 2 O + HCl → X + NH 4 Cl

Identify X from the equation

A. CH 3 COOH
B. CH 3 COCl
C. CClH 2 COOH
 D. CH 3 C H 2 OH
20. ____________ of carboxylic acids tend to have pleasant odours, so they are usually
used to make perfumes.
A. Amides
B. Esters
C. Anhydrides
D. Acy chlorides

Section B

1. Pentanol and ethanoic acid reacts in the presence of concentrated sulphuric acid to
produce ____________ which is an ester.
Answer: pentyl ethanoate
2. The most familiar carboxylic aicd is ____________ and is sometimes reffered to as
acetic acid which is responsible for the sour taste in vinegar.

Answer: ethanoic acid

3. Reactions of carboxylic acids with ammonia gives ____________ salts, which can
then be dehydrated by strong heating to give amides.

Answer: ammonium

4. Consider the reaction;

Name the product Xin the reaction.

Answer: ethanoyl chloride

5. Nitriles are ____________ to form carboxylic acids by boiling with aqueous solutions
of strong acids.

Answer: hydrolysed

6. Formic acid, systemically named _____________ acid, is the simplest carboxylic acid.
Answer: methanoic

7. From the table below, give the correct match of the functional group represented by
each molecule.

Molecule Functional group

Acyl chloride

a.
Ester

b.
Amide

c.
Carboxylic acid

d.
Anhydride

e.

Answer:

a. Anhydride
b. Acyl chloride
c. Ester
d. Amide
e. Carboxylic acid
 8. Give the organic product of the reaction of butanoic acid and phosphorous
pentachloride.

Answer: Butanoyl chloride

9. Electron withdrawing substituents on carboxylic acids makes the acid ____________

because they delocalise the negative charge of the carboxylate ion.

Answer: stronger

10. Carboxylic acids derivatives can be converted into one other or the parent acid by
nucleophilic ___________ reactions using an appropriate nucleophile.

Answer: substitution

11. Give the name of the organic product of the reaction of propanoyl chloride in
concentrated solution of ammonia in water.

Answer: Propanamide

12. Give the name of the organic product of the reaction of ethanoyl chloride and
methanol.

Answer: methyl ethanoate

13. Give the IUPAC name of the following compound;

Answer: Propanamide

14. The carboxyl group is a combination of two polar groups, the hydroxyl and
___________ groups.

Answer: carbonyl
 15. Saturated fats tend to be __________ at room temperature and are mainly from
animal sources.

Answer: solids

16. Amides are formed by reactions between acid chlorides and ammonia or a primary
or secondary ___________.

Answer: amine

Section C

1. Name and predict the structures of the organic products of the reactions between;
a. Ethanoyl chloride and phenol[2]

Answer: phenyl ethanoate

b. Ethanoyl chloride and ammonia [2]

Answer: ethanamide

c. Butanoic acid and sodium carbonate [2]

Answer: sodium butanoate

 d. propyl ethanoate and sodium hydroxide [2]

Answer: propanol and sodium ethanoate

propanol

sodium ethanoate

2. With reference to molecular structures of ethanol, phenol and ethanoic acid,

acccount for the variation in acidity of these three compounds.[7]

Answer:

 Phenol and ethanol are alcohols and ethanoic acid is a carboxylic acid.
 The acidity of carboxylic acids compared to alcohols is explained by the relative
stabilisation of the carboxylate ion by the delocalisation of electron.
 When an alcohol donates its proton, it becomes a negative ion called an alkoxide ion,
−¿¿
RO . When a carboxylic acid donates its proton, it becomes a negatively charged
ion, ROO−¿ ¿, called a carboxylate ion.
 A carboxylate ion is much more stable than the corresponding alkoxide ion because
of the existence of resonance structures for the carboxylate ion which disperse its
negative charge.
 Ethanoic acid has pKa = 4.74, alcohols have pKa ~ 16, so carboxylic acids are about
1011 times more acidic than alcohols.
 The difference lies in the fact that the carboxylate anion has the negative charge
spread out over two oxygen atoms, whereas the alcohol has the negative charge
localized on a single oxygen atom

3. Esters are neutral compounds and they undergo two types of hydrolysis that is acid
and base hydrolysis.
a. Write an equation for the acid catalysed hydrolysis of ethyl acetate.[2]
Answer:

+¿
CH 3 COO CH 2 CH 3 (l) + H 2 O(l) H CH 3 COOH (aq )¿ + C 2 H 5 OH ( aq)
⇔

b. Write an equation for the base catalysed hydrolysis of ethyl acetate.[2]

Answer:
+ ¿¿
CH 3 COO CH 2 CH 3 + NaOH →CH 3 CO O−¿ Na ¿
+ CH 3 CH 2 OH
4. Carboxylic acids are converted to acyl chlorides by their reaction with phosphorous
pentachloride (PCl¿¿ 5)¿ or by sulphur dichloride oxide(SOCl¿¿ 2)¿.
a. Draw the fully displayed structural formula for pentanoyl chloride.
Answer:

b. Write equations for the preparation of butanoyl chloride by reactions of butanoic

acid with;
I. Phosphorous pentachloride (PCl¿¿ 5)¿
Answer: CH 3 CH 2 CH 2 COOH + PCl5 →CH 3 CH 2 CH 2 COCl + POCl 3 + HCl
II. Sulphur dichloride oxide(SOCl¿¿ 2)¿
Answer: CH 3 CH 2 CH 2 COOH + SOCl2 → CH 3 CH 2 CH 2 COCl + SO 2 + HCl
5. A di-ester is formed by the reaction of ethane- 1, 2- diol and methanoic acid.
a. Draw the structural formula of the di – ester.[2]
Answer:

b. Suggest a possible catalyst for this reaction.[1]

Answer: Concentrated sulphuric acid
6. When triglycerides in fat or oil react with aqueous NaOH, they are converted into
glycerol and the salts of the respective fatty acids.
 Consider the triglycerolD below, the R groups represents carboxylic acid chains.

a. Write a balanced equation for the reaction of the triglyceride D and sodium
hydroxide.[3]
Answer:

b. The reaction in (a) is called alkaline hydrolysis of esters. Name one important
industrial use of this reaction and give the industrial name for the process.[2]
Answer: The reaction is useful in the manufacture of soaps and the process is called
saponification.
7. Given an aromatic carboxylic acid, benzoic acid, outline how one can produce the
following organic compounds. State the conditions under which they are formed and
give reactions for the formation.

a. An ester[3]
Answer:
Benzoic acid undergo a reaction with alcohols in the presence of concentrated sulphuric acid
to form an ester and water.
C 6 H 5 COOH + CH 3 CH 2 OH →C 6 H 5 COOCH 2 CH 3 + H 2 O

b. An acid chloride [4]

Answer:
Benzoic acid is converted to acyl chlorides by its reaction with phosphorous pentachloride
(PCl¿¿ 5)¿ or by sulphur dichloride oxide(SOCl¿¿ 2)¿.
Consider the reaction of benzoic acid and sulphur dichloride oxide which gives benzoyl
chloride;
C 6 H 5 COOH + SOCl2 → C6 H 5 COCl + SO 2 + HCl
8. Aspirin, also known as acetylsalicylic acid and is a medication used to treat pain,
fever, or inflammation. Consider the structure of Aspirin;

a. Identify any two functional group that are present in Aspirin.[2]

Answer: carboxyl group and ester group
b. Draw the structures of the two organic compounds that can be used to make aspirin.
[4]

and

Or

and

9. Explain the relative ease of hydrolyis of acyl chlorides, aryl chlorides and alkyl
chlorides.[10]
Answer:

 The ease of hydrolysis of acyl chlorides, aryl chlorides and alkyl chlorides rely on the
degree of electron deficiency of the carbon atom which is bonded to the halogen,
chlorine.
 In acyl chloride, the carbon atom is bonded to both chlorine and oxygen atoms
which are highly electronegative and they withdraw electron from the carbon atom.
 Therefore, the acyl chloride can readily attract nucleophiles, ¿.
 In alkyl chlorides (chloro ethane), the carbon atom to which the chlorine atom is
bonded is electron deficiency since the electrons are being withdrawn by the
chlorine atom.
 Therefore, the alkyl chloride can attract nucleophiles like OH −¿¿ but not more than
acyl chlorides.
 So ethanoyl chloride is more reactive than ethane chloride.
 In aryl chlorides (chloro benzene), the lone pair of electrons on the chlorine atom
interacts with the benzene ring and there is resonance.
 So, because of resonance, a cloud of delocalised electrons will result and it increases
the C−Cl bond strength and decreases the polarity of the bond.
 Hence, the chlorine atom in chlorobenzene cannot be removed easily as a result the
chloro benzene is almost unreactive.

10. Describe the formation of carboxylic acid from;

a. Nitriles[3]
Answer:
 The basic and acidic hydrolysis of nitriles, which are organic molecules containing a
cyano group, leads to carboxylic acid formation.
 For acid hydrolysis, the nitrile is heated under reflux with dilute hydrochloric acid.
 For example, with ethanenitrile and hydrochloric acid you would get ethanoic acid
and ammonium chloride.
CH 3 CN + 2 H 2 O + HCl →CH 3 COOH + NH 4 Cl
  For basic hydrolysis, the nitrile is heated under reflux with sodium hydroxide
solution.
 For example, with ethanenitrile and sodium hydroxide,a sodium salt is formed and
ammonia gas is given off as well.

CH 3 CN + H 2 O + NaOH →CH 3 COONa + NH 3

 To get a free carboxylic acid in this case, the final solution is acidifyed with a strong
acid such as dilute hydrochloric acid or dilute sulphuric acid.

b. Alcohols [3]
Answer:

 Primary alcohols are oxidised to carboxylic acids via aldehydes. Below is an example
of ethanol;

Reflux withexcess
CH 3 CH 2 OH + [O] H SO ∧Cr O2−¿ CH 3 CHO → CH 3 CO 2 H ¿
2 4 2 7
→

 In this reaction, ethanol is first oxidised to ethanal and the oxidation continues to
produce the ethanoic acid.