S5: Chemistry

         Key unit competency:

To be able to relate the functional groups of esters, acid anhydrides,
amides and nitriles to their reactivity, preparation methods and uses. 
• Describe the chemical properties of esters, acid anhydrides, amides, and 
   nitriles. 
• Describe the process of urea manufacture and its uses. 

• Describe the formation of the detergents.

Apply IUPAC rules to name esters, acid anhydrides, amides, and nitriles.

• Compare the physical properties of esters to those of alcohols and carboxylic 
   acids. 
• Make a soap and compare its properties with those of soapless detergents. 
• Compare the reactivity of acid anhydrides with those of acyl chlorides. 
• Prepare aspirin from appropriate reagents.
• Appreciate the importance of esters, acid anhydrides, amides and nitriles in 

   textile industry and pharmacy. 

    Introductory activity

The development of organic chemistry has led scientists to the production of 
new substances and materials that are necessary in our everyday life which 
could not be provided by our natural environment. Others were produced to 
satisfy the high demand of consumers which cannot be assured by natural 
products only. Analyze the items presented below and answer the questions 

listed down.

               

1. What kind of textile is used to make umbrellas? How did scientists make 

    this kind of textiles? 

2. One of the substances used to improve soil fertility so as to ensure food 
    security is urea? How is it synthesized?
3. Why is it possible to make artificial drinks with flavors of natural fruits?
4. How are pain killer drugs manufactured?

5. What kinds of substances provide perfumes with their fragrances? 

8.1. Structure and nomenclature of esters

      Activity 8.1

3. The compounds listed below contain acid derivatives and other organic 

      molecules. Classify them in the following table. 

                             

    2.Draw all possible isomers with molecular formula   and label esters 

        with letter A and acids with letter B. 

      8.1.1. Structure of esters

In unit 7, the reactions of carboxylic acids were discussed. The reactions of carboxylic 
acids produce the derivatives of acids such as esters, acid halides, acid anhydrides 

and amides.

The general molecular formula of esters is  and their general structural 

  formula is: RCOOR’ or

                                      

Where R may be a hydrogen atom or an alkyl group and R may be an alkyl group 
or an aryl group but not a hydrogen atom. In case that R is the hydrogen atom, the 
compound is no longer an ester but it is a carboxylic acid.
The following Figures, 8.1 and 8.2 show models for two common esters where green 
spheres = Hydrogen atoms, red spheres = oxygen atoms; blue spheres = carbon 

atoms.

                       

The functional group of esters is 

Esters are compounds produced by the reaction involving an acid and an alcohol 

with the elimination of water molecule.

For example, the reaction between acetic acid and ethanol yields an ester 

with water.

              

Esters are known for their distinctive odor and they are commonly responsible for 
the characteristic of food (fruits) aroma, flowers and fragrances. Esters are found in 
nature but they can be also synthesized. Both natural and synthetic esters are used 

in perfumes and as flavoring agents.

8.1.2. Nomenclature of esters

The nomenclature of esters follows some steps. When naming esters the alkyl 
group R’ is named followed by the name of RCOO- group. 
The group name of the alkyl or aryl portion is written first and is followed by the 
name of the acid portion. In both common and International Union of Pure and 
Applied Chemistry (IUPAC) nomenclature, the -ic ending of the corresponding acid 
is replaced by the suffix –ate. Some examples of names of esters are given in Table 

8.1.

        Examples:

        

         Table 8.1. Examples of structural formulae of some esters and their name

   8.1.3. Physical properties and uses of Esters

       Experiment 

A. Analyzing the solubility of esters ( fats and oils)
Materials and Chemicals
Cooking oil, margarine, water, ethanol, stirring rods and test tubes labeled A 
and B. 

Procedure
1. Pour water in a test tube A and ethanol in test tube B and add some 
    cooking oil in each test tube. Shake well to mix and record your 
    observation.
2. Pour water in a test tube A and ethanol in test tube B and add a small 
    piece of margarine in each test tube. Use a stirring rod to mix and record 
    your observation. 

Conclusion: Esters are soluble in organic solvents such as ethanol and insoluble 

in water.

B. Comparing boiling points of alcohols, carboxylic acids and esters

      Materials and Chemicals

       Propan-1-ol, propanoic acid and methyl ethanoate, test tubes, test tube holders 

       (lacks), heaters, and thermometers.

Procedure

1. Put 10 mL of each substance in a labeled test tube.
2. Boil carefully substances are volatile and flammable
3. Use a thermometer to measure the boiling point of each substance.
4. Record the results and compare them. Suggest a reason for the difference 
    in boiling points of the three substances.

Conclusion: Esters have lower boiling points than alcohols and carboxylic 
acids because they lack hydrogen bonds. A compound having hydrogen bonds 
has a high boiling point because, to break that bond requires higher energy. 

Other physical properties of esters
i. Lower esters have sweet fruity smells
ii. Melting and boiling points of esters increase as the molecular mass 
    increases. 
iii. Small esters are fairly soluble in water but the solubility decreases as the 
      length of the chain increases 

8.1.4. Uses of Esters
Esters find various uses:
i. They are used as organic solvent
ii. Due to their aroma, they are used as constituent of fragrance, essential oils, 
     food flavoring and cosmetics.
iii. They are used to manufacture soaps, detergents and glycerol. 
iv. They are used to provide energy in the body

v. Polyesters are used to produce plastics etc

Checking up 8.1

1. Name the following compounds by using the common and IUPAC 

     names.

              

2. Draw the structural formulae corresponding to each of the following 
      names.
i. Propyl methanoate 
ii. octyl ethanoate
3. Discuss the solubility of esters 
4.State one industrial and one biological use of esters. 
5.Two compounds A and B of molecular formula  were analyzed 
    to compare their relative boiling points. Compound A had lower boiling 
    point than compound B. Draw the structural formula of each compound. 
6.Identify the relationship that exists between compounds A and B. Explain 

    your reasoning.

8.2. Preparation and chemical properties of esters

              

3. Using your research on internet and reading books, make a summary of 
    each of the following terms: 
e. Reduction of esters 
f. Hydrolysis of esters
g. Alkaline hydrolysis of ester
h. Trans-Esterification 
i. Comparison of the reactivity of esters, acid chlorides and acid 
    anhydrides
4.Give an example of an equation for each of the processes in (1).

 5. Express the technical name given to the process in 3 (c)

8.2.1. Preparation of Esters
The preparation of esters involves different types of reaction such as esterification, 
reaction of an acid chloride with an alcohol and the reaction of acid anhydrides 
with alcohols.

1.Esterification reaction
In units five and seven, it is mentioned that esters can be produced by a reaction 
between alcohols and carboxylic acids in strong acidic medium acting as a catalyst. 
The acid is commonly a concentrated sulphuric acid, under reflux (Figure 8.3). The 
reaction is generally called “Esterification” (a condensation reaction which involves 
the addition of the alcohol and acid molecules followed by an elimination of a 

water molecule).

        

                      

3. Reaction of acid anhydrides with alcohols ( Trans-esterification)
Alcohols react with esters to undergo an exchange of the alkoxide segment. The 
reaction is acid catalyzed and the used alcohol must be in excess. This is a very 

common technique of producing new esters from available esters.

                      

              

Reaction mechanism

                      

          

          2. Reaction of an acid chloride with an alcohol

               

             

             8.2.2. Chemical properties of esters

      Chemical properties of esters involve their reactivity with other compounds.

          a. Reduction of esters

Compared to ketones and aldehydes, esters are relatively resistant to reduction.
Esters are reduced by giving two alcohols,
one from the acyl segment (RC=O) and one from the alkoxide segment (R-O) as 

shown by the reaction below.

           

When a less reactive reducing agent such as diisobutylaluminium hydride (DIBAH) is 
used the acyl segment is converted into an aldehyde and the alkoxide group is still 
converted into an alcohol. Exactly one equivalent of the hydride must be used, and 

the reaction must be carried out at -78 °C

                 

b. Hydrolysis of esters.
The reaction of an ester with water is called hydrolysis. This reaction is very slow 

unless catalyzed by a base or an acid.

                 

Mechanism of basic hydrolysis ofeEsters

               

The base catalyzed hydrolysis reaction is called saponification (derived from Latin 
word, “sapo”, which means soap). Soaps are sodium or potassium salts made by 
hydrolyzing the vegetable oil which contain higher molecular weight esters in the 

presence of sodium or potassium hydroxides.

              

c. Trans-esterification
Alcohols react with esters to undergo an exchange of the alkoxide segment. The 
reaction is acid catalyzed and the used alcohol must be in excess. This is a very 

common way of producing new esters from readily available esters. 

        

          

          d. Reaction with amines: Aminolysis
Esters react with ammonia, primary or secondary amines to produce amides. The 
reaction is carried out at high temperature in basic medium. However, this reaction is 

not often used because higher yields are normally obtained by using acyl chlorides.

        

             

e. Reaction with Grignard reagents

Esters react with two equivalents of a Grignard reagent to form tertiary alcohols. This 
reaction produces ketone intermediates which undergo a fast conversion into the 

alcohol because of being more reactive than esters.

        

Checking Up 8.2.

1. Write a balanced equation for the reaction between propanoyl 
chloride and butan-1-ol and name the product. 

2. Investigate how to carry out the following conversions by using a 
   non-organic compounds other than the one cited. Use any inorganic 
     substances you need. 
a. Propan-1-ol to propyl propanoate
b. Ethanal to ethyl ethanoate 

3. Ethanoic acid reacts with an alcohol of molecular formula C4H10O to 
produce an ester which is optically active. 
a. Identify the structure of the alcohol. 

b. Sketch the structure of the ester formed.

4. Complete the equations below:

       

5. For a reaction to take place, some conditions may be required 
     depending on the type of reaction. Discuss the conditions to be used 

     in order to carry out the reaction 4.a.

6. Reactions of amines with esters are not common 
     Explain briefly this statement.
7. You are provided with ethyl ethanoate and asked to prepare isobutyl 
    ethanoate.
Describe how you can proceed to prepare that compound. In your 
explanations, include reagents, conditions and equation(s) for the reaction(s) 
that take place. 

 You are allowed to use any other organic compound you need. 

8.3. Saponification and Detergents

        

Observe the above picture and answer the following questions

1. Explain the properties that these products have which make them 
      suitable for their use as you have stated in (1).
2. Explain how these products are manufactured?
3. Propose the differences and similarities of these products? 
4. Using NaOH and cooking oil, how can you prepare a solid soap in 

    laboratory? 

Surfactants like soaps and detergents are important cleaning products which play 
an essential role in our daily life. By safely and effectively removing soils, germs and 
other contaminants, they help us to stay healthy, care for our homes and possessions, 
and make our surroundings more pleasant.

Soaps
Soaps are water-soluble sodium or potassium salts of fatty acids. Soaps are made 
from fats and oils, or their fatty acids, by reacting them with a strong alkali. The 
process is known as “saponification”.

Fats and oils
The fats (solid lipids at room temperature and pressure) and oils (liquid lipids at 
room temperature and pressure) used to produce soaps find their sources from 
animal or plant. Each fat or oil is made up of a distinctive mixture of several different 
triglycerides.

In the formation of a triglyceride molecule, three fatty acid molecules reacted with 

one molecule of propane-1,2,3-triol or glycerol as shown in Figure 8. 4 below. 

           

            

            Saponification reaction

The reaction of saponification involves the collision between triglycerides in fat/oil 

and aqueous NaOH or KOH. The result is the formation of soap and glycerol (Figure 8.5).

            

                   

The reaction of saponification is exothermic because there is liberation of heat and 
the soap formed remains in suspension form in the mixture. Soap is precipitated as 

a solid from the suspension by adding common salt to the suspension. 

            

Note: Sodium soaps are “hard” soaps whereas potassium soaps are soft.

DETERGENTS

Detergents are organic liquid or water-soluble solid cleaning substances that, unlike 
soap, are not prepared from fats and oils. 

The chemical composition of detergents is different from that of soaps but they 
have the same cleaning mechanism and are not adversely affected by hard minerals 
in the water and this makes them more effective than soaps. However, they are less 
environmental friendly because of a reduced biodegradability.

Detergents may be used for household cleaning, laundry or for body and hand 
washing. They exist in the powder or liquid form.

How do soaps and detergents work?
When a soap or detergent is added to water, a polar solvent, the molecules form 
clusters, known as micelles(Figure 8.6), in which the polar ends of the molecules are 

on the outside of the cluster and the non-polar ends are in the middle.

         

The carboxylate end of the soap molecule is attracted to water. It is called the 
hydrophilic (water-loving) end. The hydrocarbon chain is attracted to oil and grease 
and repelled by water. It is known as the hydrophobic (water-hating) end. When 
washing, the hydrophobic part of the soap molecule (Figure 8.7) dissolves oil or 
grease the main source of dirt and it gets washed away by water as it is insoluble in 

it. 

The other major soap-making process is the neutralization of pure fatty acids with 

an alkali.

       

The cleaning property of both soaps and detergents results from their capacity 
to emulsify water-insoluble materials (dirt, oil, grease, etc.) and hold them in 
suspension in water. This ability originates from the molecular structure of soaps 
and detergents. When a soap or detergent adds on to water that contains oil or 
other water-insoluble materials, the soap or detergent molecules surround the oil 
droplets. The oil or grease is “dissolved” in the alkyl groups of the soap molecules 
while the ionic end allows the micelle to dissolve in water. As a result, the oil droplets 
are dispersed throughout the water (this is referred to as emulsification) and can be 

rinsed away.

            

                        Difference Between Soap and Detergent

             

Checking Up 8.3.

1. Propyl tristearate reacts with sodium hydroxide to form soap.
a. Write a balanced equation for the reaction which takes place.
b. Calculate the mass of sodium hydroxide needed to react exactly with 
     4kg of this oil and the mass of the produced soap.

2. Describe the chemical difference of solid and liquid soaps.
3. Distinguish soaps from detergents.
4. Why are detergents more effective than soaps?
5. Describe briefly in your own words how soaps and detergents work.

6. Discuss the importance of soaps and detergents in our everyday life.

8.4. Structure and nomenclature of acid anhydrides

        

One of the most used pain killers is aspirin. This is a medical drug which can be 
prepared using salicylic acid and ethanoic acid. However, ethanoic acid is not 
used. Instead, one of its derivatives is used. Search from internet or the school 
library and answer the questions below:

1. Propose a derivative of acetic acid is used in this preparation?
2. Explain why is it used in preference to acetic acid?
3. Write down its molecular formula and structure. 

4. Suggest how it is produced from acetic acid.

8.4.1. Structure of acid anhydrides

The acid anhydrides are derivatives of carboxylic acids.
The general structure of acid anhydrides is RCOOOCR, or
   When the two R groups are identical, the acid anhydride is symmetric and when the 

two R groups are different, the acid anhydride is asymmetric. The general molecular 

formula of acid anhydride is                          
The functional group of acid anhydrides consists of two acyl groups held together 

by an oxygen atom. 

                    

When the two R groups are identical, the acid anhydride is symmetric and when the 
two R groups are different, the acid anhydride is asymmetric. The general molecular 

formula of acid anhydride is  

8.4.2. Nomenclature of acid anhydrides

The nomenclature of acid anhydride is based on whether they are symmetrical or 
unsymmetrical. Symmetrical acid anhydrides are named as parent acid followed by 

the term anhydride

            

                

Unsymmetrical acid anhydrides are named by writing alphabetically the names of 

parent acids followed by the term anhydride. 

           

Checking up 8.4.

1. Write the molecular formula of an acid anhydride which has 6 carbon 
     atoms
2. Draw the structure of one straight and one branched isomers of the 
    molecular formula in (1) above. 

3. Name the isomers from (2).

8.5. Preparation, chemical properties and uses of acid anhydrides

Activity 8.5.

1. Two carboxylic acids can react to form an acid anhydride and a water 
     molecule. However, this method is not suitable when preparing mixed 
    (unsymmetrical) acid anhydrides. 
2. Suggest a reason why this method is not suitable. 
3. Using your knowledge in organic chemistry so far, suggest a method 
     which may be suitable to prepare ethanoic propanoic anhydride. Write 
     the equation for the reaction. (Hint: you may refer to the preparation of 
     ethers). 
4. Prepare ethanoic anhydride using ethanoic acid and phosphorous 
    pentoxide.
5. Aspirin is synthesized using ethanoic anhydride and salicylic acid. Suggest 

    an equation for the reaction that occurs. 

8.5.1. Preparation

Anhydride means “without water”. Two carboxylic acids can react, eliminating a 

water molecule to yield an acid anhydride.

     

The commonly used dehydrating agent is phosphorous pentoxide, If two 
different acids are used, a mixed anhydride is produced. The method is less efficient 
however, as one obtains the two symmetrical anhydrides in addition to the desired 
mixed anhydride. 

A better method of making mixed anhydrides is to react an acid halide with a salt 

of a carboxylic acid. This method can be used to make symmetrical anhydrides too.

          

8.5.2. Chemical properties of acid anhydrides and their uses 

The term “chemical properties” indicates the reactivity between two or more 
compounds. In the case of acid anhydrides, their reactivity involves the electron                                                                             deficient carbonyl-carbon which is attacked by nucleophiles. This reaction occurs slowly.

There are mainly four types of reactivity of acid anhydrides such as hydrolysis, reaction 
with alcohols, reaction with ammonia and amines and the reduction reaction.

1. Hydrolysis
This reaction of acid anhydride in water leads to the formation of parent carboxylic 
acids which were used to prepare the anhydride. The reaction is carried out in acidic 

medium under reflux. 

            

            

2. Reaction with alcohols 

Anhydrides react readily with primary, secondary, tertiary alcohols to form esters 

and carboxylic acid.

               

Aspirin synthesis is an application of this reaction

                  

This reaction is very important in pharmaceutical industries and it indicates the 

main use of acid anhydrides as it is the basis of aspirin manufacture as shown below.

                    

 3. Reaction with ammonia and amines

Anhydrides react with ammonia, primary and secondary amines to produce 
amides. 
The reaction with amide: 

            
        
         Reaction with ammonia: (RCO)2 O + NH3 → RCONH2 + RCOOH

            
            
             4. Reduction of acid anhydrides
Anhydrides are reduced by Lithium tetrahydridoaluminate, 
to yield two moles of primary alcohols. 

            
 Where R and R can be hydrogen atoms (for primary amides), alkyl groups (for 

tertiary amides). For secondary amides only one R is a hydrogen atom. Their general 

molecular formula is Cn

H2n+1ON. Examples of some amides are given in the Table 8.2.

       

8.5.3. Uses of acid anhydrides

1. Ethanoic anhydride is used in the synthesis of acetate esters. 
2. Examples: aspirin, cellulose acetate,…
3. Maleic anhydride is used in the synthesis of various resins when 
    copolymerized with styrene.

4. They are used to synthesize polyesters and polyamides.

Checking up 8.5 

1. Write the equations that can be used to synthesize the following acid 
anhydrides from ethanol.
a. Ethanoic anhydride 
b. Propanoic anhydride 
c. Ethanoic propanoic anhydride
2. Students of senior five MCB were asked to prepare butanoic propanoic 
    anhydride and group A used a method similar to Williamson’s method of 
     synthesizing ethers whereas group B decided to use a dehydrating agent. 
     Which group chose a better method? Explain your reasoning

3. Complete the equations below

       

4. Propose the products from the reaction below:

     

5.Draw the structures of products formed when propanoic anhydride reacts 
    with 2-methylpropan-2-ol
6. State the necessary chemicals and conditions to prepare aspirin.
7.Chemists prefer using acid anhydrides than acyl chlorides when preparing 

    esters. Discuss this statement. 

8.6. Structure and nomenclature of amides

Activity 8.6.

In the previous unit, it has been mentioned that carboxylic acids react with 
ammonia and amines to produce new organic compounds.
1. Draw and name their functional group.
2. Draw their general structure and determine their general molecular 
    formula. 
3. What natural and artificial polymers contain the same functional group?
4. Suggest how their boiling points would be relative to those of esters. 

Provide an explanation for your suggestion. 

8.6.1. Structure of amides

 Amides are acid derivatives in which the –OH group is replaced by  or
. The functional group comprises nitrogen atom which is attached to the 
carbonyl carbon atom. The carbonyl group linked to nitrogen atom is called an 

amide linkage. The general structure of amides is:

                             

Where R and R can be hydrogen atoms (for primary amides), alkyl groups (for 
tertiary amides). For secondary amides only one R is a hydrogen atom. Their general 
molecular formula is       ON. Examples of some amides are given in the Table 8.2.

                      Table 8.2. Examples of some amides

            

8.6.2. Nomenclature of amides

The nomenclature of amides is derived from the name of corresponding acid. The 
–oic acid suffix or –ic acid is replaced by –amide.
 
As for other organic compounds, the first step is to consider the number of carbon 
atoms forming the chain.

The alkyl group bonded to nitrogen atom is indicated by a capital N preceding the 

alkyl name. 

              

8.6.3. Physical properties and uses of amides

Physical properties of amides
Except formamide, all the amides are crystalline solids at room temperature. Amides 
have higher melting and boiling points than corresponding esters due to hydrogen 

bonding as shown below. 

                

The melting and boiling points increase as molecular mass increases. Lower members 
are soluble in water but this solubility decreases as the molecular mass increases. All 
the amides are soluble in organic solvents. The Table 8.3 shows the comparison of 

melting and boiling points of some amides.

Table 8.3. Some physical properties of lower amides

       

8.6.4. Uses of Amides

Amides are used in the production of many useful chemicals and materials such as 

fertilizers (urea), nylon textiles and skin care substances. 

              

Urea manufacture
Urea can be prepared in three ways:

a. Reaction of phosgene and ammonia 

                

The diagram below shows the representation of Urea.

               

b. From calcium cyanamide,

Calcium carbide reacts with nitrogen to produce calcium cyanamide and carbon. 
  produced is then treated with a mixture of water 

and carbon dioxide to produce urea.

         

c. Reaction of carbon dioxide and ammonia

              

Urea is also naturally present in animal urines.
It is widely used in agriculture as a source of nitrogen, chemical fertilizer. It also finds 
use in animal feeding and in resins manufacture. 

Nylon manufacture
Nylon-6,6 is a synthetic textile produced when hexane-1,6-dioic acid(adipic acid) 
reacts with hexane-1,6-diamine. Nylon is a polyamide. Materials and clothes are 

made from nylo-6,6.

             

Medical use of urea

Urea containing creams are used in skin treatment to promote its rehydration. It softens the 

skin. 

Checking up 8.6.

1. Write the molecular formula of amides with 4 carbon atoms
2. Draw all possible structural formulae of primary, secondary and tertiary 
     amides with molecular formula in (1) above and name them
3. Compare the solubilities of butanamide and N,N-dimethylethanamide 
     in water 
4. The solubility of amides decreases with the increase in molecular mass. 
     Suggest a reason for this observation.
5. Which one between ethanol and ethanamide do you expect to have a 
    higher boiling point? Explain your answer. 
6. Discuss the benefits and dangers of using animal urine as a source of 

     nitrogen for plants.

8.7. Preparation and chemical properties of amides

Activity 8.7.

1. Draw the structure of propanamide.
2. Suggest how this compound can be prepared from propanoic acid. 
     Include an equation in your answer and state working conditions. 
3. Draw the structure of ethanoyl chloride and write an equation for its 
    reaction with 
4. Suggest other possible reactions that can be used to prepare amides in 
     general

5. What reagents and conditions which can be used to reduce amides?

8.7.1. Preparation of amides

Amides can be prepared from all of the other acid derivatives when they react with 
ammonia and primary or secondary amines. Their production of amides involves 

the following reactions.

               

            

 8.7.2. Chemical properties of amides

The reactivity of amides involves different types of reaction to form various organic 

compounds. 

1. Reduction reaction

Amides are reduced with sodium and ethyl alcohol or with lithium aluminium 

hydride   to yield primary amines.

             

          

2. Hydrolysis

Amides react with water in acidic medium (dilute) at high temperatures to form 

acids.

        

          

         

3. Hoffman degradation

Amides react with a mixture of sodium hydroxide and bromine or sodium 
hypobromite to produce amines. The reaction is called degradation as the carbon 

chain is reduced by one carbon.

    

      

This equation can be simplified as follows:

         

Note: Hoffman degradation reaction is used to test the presence of the amide 
functional group. When an amide is treated with sodium hypobromite, a 

colorless gas which turns milky lime water is evolved, 

4. Reaction with nitrous acid

Amides react with nitrous acid to produce an acid, water and nitrogen gas.

       

         

5. Dehydration reaction

Dehydrating reagents, like thionyl chloride   remove one molecule of water 
from amides to give nitriles. Phosphorous pentoxide can also be used. The reaction 

is done under reflux.

       

        

        

8.8. Structure and nomenclature of nitriles

Activity 8. 8.

In the previous lesson of this unit you learnt different reactions of amides. From 

your knowledge and understanding, answer the questions that follow:

1. Draw the structure of compound A:

             

2. To what homologous series does product A belong?
3. Write the molecular formula of A.
4. Suggest the general structure and the general molecular formula for all 
    compounds belonging to the same homologous series as A.
5. At room temperature, these compounds are liquids or solids depending 
    on the molecular mass and yet they lack hydrogen bonding. Suggest a 

     brief explanation for this specialty. 

8.8.1. Structure of nitriles

Nitriles are organic compounds with the general structure is its 
functional group. The nitrile compounds include a nitrogen atom attached to a 
carbon atom by a triple covalent bond. Their general molecular formula is

Unlike other acid derivatives they do not contain an acyl group.

8.8.2. Nomenclature of nitriles

The nitriles are named using the name of the alkane parent followed by the term 
–nitrile. The carbon attached to the nitrogen atom is given the location position 

number 1.

Structure and name of some nitriles are shown in the Table 8.4.

              

8.8.3. Physical properties and uses of nitriles

Physical properties

The physical properties of nitriles are summarized below.
1. The nitrile compounds are present as colorless solids and liquids having a 
    characteristic odor.
2. Nitriles have boiling points ranging between 82 and 118 °C. The high 
boiling points are due to strong dipole-dipole moments caused by the 
polarity of the C N bond.
3. Nitriles compounds exhibit high polar and electronegativity
4. Lower nitriles are highly soluble in water but this solubility decreases 

with the increase in molecular mass as the non-polar part becomes lager.

Uses of nitrile compounds

Nitriles find many uses:
• Nitriles are used in the manufacture of nitrile gloves, seals, and pipes or tubes 
   as they exhibit resistance to chemicals.
• They are used as an antidiabetic drug which is used in the treatment of breast 
   cancers.
• This compound is found in many plant and animal sources.
• They are utilized in the applications of oil resistant substances and also for 
   low-temperature uses
   They are also employed in automotive systems, hydraulic tubes and also in aircraft 

    systems.

Checking up 8. 8

1. Draw the structure of each of the compound below:
a. Butanenitrile
b. 3-methylpentanenitrile

2. Name these compounds:

                

3. Draw all possible isomers of molecular formula   and name them.

8.9. Preparation and chemical properties of nitriles

Activity 8. 9

One method of preparing nitriles is to dehydrate an amide. 
1. Use your knowledge about chemistry of alkyl halides and suggest 
     another preparation method. 
2. Name the reaction mechanism involved in that method
3. Write an equation of the preparation of propanenitrile using the method 

    you have suggested.

8.9.1. Preparation of nitriles

Nitriles are prepared by dehydration of amides under reflux in the presence 
of phosphorous (V) oxide, or sulphur dichloride oxide, 

 and there is elimination of water molecule. 

1.Dehydration of amides

          

2.Nucleophilic substitution of halogenoalkanes

The halogenoalkane is heated under reflux with a solution of sodium or potassium 
cyanide in ethanol. The halogen is replaced by a -CN group and a nitrile is 

produced. 

        

         

8.9.2. Chemical properties of Nitriles

Nitrile compounds undergo various reactions. Nitriles are hydrolyzed in the 
presence of an acid or a base to form carboxamides and carboxylic acids. This is 
the reason why they are considered to be acid derivatives while they have no acyl 

group.

1. Hydrolysis

       

           

          2. Reduction reaction.

Nitriles can be reduced by  to produce primary amines in the presence of 

catalysts such as 

          

      

Checking up 8. 9.

1. An aldehyde of molecular formula   reacts with hydrogen cyanide 
in strong basic medium to give compound A. compound A undergoes a 
reduction to give compound B. 

a. Suggest a reducing agent which can be used to reduce A.

b. Draw the structure of the product formed when compound A is treated with hot acidified water

2. What is meant by the term hydrolysis?
3. Nitriles are considered to be acid derivatives even though they do not 
     have the acyl group. Search from the internet or library a reason for this 

     consideration.

8.10. End Unit assessment

Part I: Objective questions
1. The esters are ……. acyl chlorides
d. more reactive than
e. equal in reactivity
f. less reactive than 

2. Secondary amines react with acid chloride to give
a. amines
b. carboxylic acids
c. amides
d. imines

3. A mixture of acetic acid and propanoic acid undergo dehydration to give
a. acetic anhydride
b. propanoic anhydride
c. acetic and propanoic anhydrides
d. acetic, propanoic and acetic propanoic anhydrides

4. Ethanoyl bromide reacts with sodium propanoate to give
c. ethanoic anhydride
d. propanoic anhydride
e. ethanoic propanoic anhydride
f. all of the above

5. Esters are made from the reaction between
a. carboxylic acid molecules
b. alcohol molecules
c. alcohol and carboxylic acid molecules
d. acid anhydride and water molecules

 6. Ethyl acetate is hydrolyzed by water to give a/an
a. lactone
b. ester
c. acid anhydride
d. carboxylic acid and an alcohol

 7. The reaction between ethyl ethanoate and dimethylamine gives an
a. amide
b. imide
c. acid anhydride

8. 
 reduces Ethanamide to give a/an
a. carboxylic acid
b. amide
c. alcohol
d. amine

9. Nitriles can be hydrolyzed with water to give
a. alcohols
b. aldehydes
c. acids

d. acids and amides

10. Reduction of nitriles gives 
e. amide
f. amine
g. imine
h. carboxylic acids

Part II: Structured questions
1. Use equations to show how you could prepare the following compounds, 
     using the 
    organic compounds cited as the only organic substances and any inorganic 

     substance you need:

           

                 

 5. Draw the structural formula of:
       a. 2-chloropropanamide
       b. Methylpentanoate
      c. Butanoic anhydride
      d. Propanoyl chloride
      e. N-ethyl-N-propylbutanamide

6. Give the organic products of the following reactions:
     a. Propanoic acid and ammonia. 
     b. Ethanoyl chloride plus methanol.
    c. Butanoic anhydride plus water. 
   d. Propanamide plus sodium hypobromite
    e. Ethanol plus propanoyl chloride

7. Give reagents, essential conditions and equations for the conversion of 
     ethanoic acid into:
    a. Ethanoic anhydride
    b. Ethanamide
    c. Ethyl ethanoate
8. Ethanoic anhydride is a liquid at room temperature but Ethanamide is a 
     solid. Comment briefly on this.

9. Discuss the uses of esters. 

10. a. Write an equation for the formation of ethyl ethaonate from ethanoyl 
       chloride and ethanol. Name and outline the mechanism for the reaction 
       taking place.
      Explain why dilute sodium hydroxide will cause holes in clothing made from 
      polymers such as terylene while polythene containers can store caustic soda.

11. Ethyl oleate is an ester with the molecular structure below:

           

It is possible the body could synthesize this compound from the ethanol present 
in alcoholic drinks and the natural fatty acid, oleic acid.

a. Write the structural formula of oleic acid
b. Construct a balanced equation for the production of ethyl oleate from 
     ethanol and oleic acid.

c. Suggest how oleic acid can be obtained from the triglyceride below

                

12.This question is about the reactions of carboxylic acids and their derivatives.
a. A carboxylic derivative X was found to contain C, H, N and O. analysis 
     gave the following percentage composition by mass: 49.4%, 9.6% and 
    19.1% for carbon, hydrogen and nitrogen respectively. Compound X had 
     a relative molecular of 73.
     i. Calculate the empirical and molecular formulae of X.
    ii. Suggest three possible structures of X.
b. Acyl chlorides such as ethanoyl chloride undergo several reactions due 
    to their high reactivity. What could be produced when ethanoyl chloride 
    reacts with:
c. A and B are two isomeric amides which can be hydrolyzed in acidic medium.            
    i. Water
   ii. Propan-2-ol
   iii. Ammonia

   iv. Sodium acetate

     

     i. Draw the structures of the products formed from hydrolyzing A and B.
    ii. What is the structure of the compound produced when A reacts with 
         sodium hypobromite?

    iii. Write an equation for the reaction of B with ethanoyl chloride.