S5: Chemistry

        Key unit competency:

To be able to compare the physical and chemical properties of alcohols and ethers to 

their preparation methods, reactivity and uses.

Learning objectives: 

• Distinguish between alcohols from other organic compounds by 
   representing the functional group of alcohols
• Classify primary, secondary and tertiary alcohols by carrying out the method 
    of identification
• Write the name of alcohols by using IUPAC system
• Describe the physical properties of alcohols to other series of organic 
  compounds 
• Carry out the method of preparation of alcohols 
• Describe the local process of making alcohol by fermentation.
• Explain the effect of oxidation on urwagwa when it overstays 
• Compare the physical, chemical and the method of preparation of alcohols to 
   ethers

• State the use of ethers

Introductory activity

The following represent two pictures or pictures A and B. Observe each picture 

carefully and answer to the related questions.

            

1. Discuss the meaning of each picture.

2. What objects do you observe in the above pictures?

3. Explain the consequences that can arise from the picture B

5.1. Definition and nomenclature

      Activity 5.1

1. Look at the following compounds and classify them in their 

    homologous series.

            

2. By doing your own research, distinguish the rules used to name 

    alcohol compounds.

     5.1.1. Definition

Alcohols are organic compounds that are derivatives of hydrocarbons where one 
or more hydrogen atoms of hydrocarbon is or are replaced by hydroxyl (-OH) group. 

They are represented by the general formula:

where R is a radical: alkyl group made by a chain of carbon atoms

Alcohols are called monohydric if only one hydroxyl group is present 
 Dihydric alcohols are those with two hydroxyl group
(diol: vicinal and gem), trihydric (triols) and polyhydric are those with many – C-OH groups.
The functional group attached is –OH group to any atom of carbon.

   5.1.2. Nomenclature

 According to IUPAC system, alcohols are named by replacing the final ‘‘e’’ of the 
parent hydrocarbon with ‘‘ol’’, then specify the position of -OH group before ending 

by ol.

               

1. Write the structural formulas of all organic compounds containing 
   C-OH group and fit the molecular formula
2. Based on their structures and your knowledge about classes of 
    halogenoalkanes, classify the compounds identified in 1) above.
3. Classify them as chain and position isomers.

4. Which of them can exhibit optical isomerism?

Alcohols are classified as: 
Primary alcohols: These have only one alkyl group attached to the carbon 

carrying the –OH.

Examples

           

Secondary alcohols: they are alcohols in which the OH group is attached to carbon 

atom bonded to two other carbon atoms.

               

Tertiary alcohols: they are alcohols in which the OH group is attached to carbon 

atom bonded to three other carbon atoms. 

                     

Alcohols containing at least three carbon atoms exhibit different types of isomerism:

• Chain isomerism: 

This is due to the difference in the size of the chain.

                              

• Position isomerism: 

This is due to different positions taken by the –OH in the same carbon chain.

                

• Functional isomers: 

Except methanol which has one carbon, other alcohols are isomers with ethers 
another chemical function of general formula R-O-R’
 where R and R’ are alkyl groups 

or aryl groups but not hydrogen.

         

5.3. Physical properties

         Activity 5.3.

     Analyze the following data and answer to the question

     

     Explain the trends in the boiling point of the molecules given in the table

     Compare and explain the differences in the boiling point of alkanes and alcohols

     a. Boiling points

The chart shows the boiling points of some simple primary alcohols and alkanes 

with up to 4 carbon atoms.

          

                              Figure 5.1: boiling points of alcohols and alkanes   

  • The boiling point of an alcohol is always much higher than that of the alkane 
    with the same number of carbon atoms.

• The boiling points of the alcohols increase as the number of carbon atoms 
   increases.

• The boiling point of alcohols with branches is lower than that of unbranched 
   alcohols with the same number of carbon atoms. This is because increased 
    branching gives molecules a nearly spherical shape and the surface area 
   of contact between molecules in the liquid. This results in weakened 
   intermolecular forces and therefore in lower boiling points.

• Tertiary alcohols exhibit the lowest boiling point than secondary and primary 
    alcohols:

• Primary alcohol        > Secondary alcohol                         > Tertiary alcohol
 Highest boiling point                                                                      lowest boiling point

The patterns in boiling point reflect the patterns in intermolecular attractions: 
In the case of alcohols, there are hydrogen bonds set up between the slightly positive 

hydrogen atoms and lone pairs on oxygen in other molecules.

                             

 b. Solubility of alcohols in water

The lower members of alcohols are completely soluble in water because mixed 
hydrogen bonds between water and alcohol molecules are formed. As the length of 

hydrocarbon group of the alcohol increases, the solubility decreases.

c. Volatility

Alcohols are volatile and the volatility decreases as the molecular mass increases. 
Compared to alkyl halides, alcohols are less volatile. Polyalcohol are viscous or solids. 
Example: propane-1, 2, 3-triol (glycerine). This is due to stronger intermolecular 

forces than those of mono alcohols.    

Checking up 5.3

1. Comment on the solubility of alcohols compared to alkanes in water.

2. Ethanol with a molecular mass of 46 and butane with a molecular mass 

    of 58 have the boiling point of   respectively. 

    Explain these differences.

3. Are alcohols electric conductors? Justify your answer. 

5.4. Alcohol preparations

       Activity 5.4

Complete the following chemical equations. For each, show the mechanism of 

the reaction 

                     

   Alcohols are prepared with different methods

   a. From alkyl halides

Alkyl halides when refluxed with aqueous alkali (NaOH or KOH) or moist silver 
oxide (Ag OH) produce alcohols. The hydrolysis occurs by a nucleophile substitution 

reaction. 

                     

Note: During the reaction of these preparations of alcohols, you have to use the 
dilute NaOH, KOH and warm in order to increase the rate of   
 for primary alcohol while tertiary alcohols undergo 

b. From alkenes
Alkenes react with water in the presence concentrated sulphuric acid to yields 

alcohols

                

Notice: Alkenes in the presence of Aluminum oxide reacts with water to form 

alcohols in vapour phase then condense to give liquid alcohols.

                      

c. From carbonyl compounds

When aldehydes and ketones are reduced by hydrogen in the presence of a suitable 

catalyst like Pt, Ni or Pd, they form primary and secondary alcohols respectively.

                

                

     Note: Lithium tetrahydridoaluminate (LiAlH4 ) can also be used as a reducing agent.

                 

 Lithium tetrahydridoaluminate is not a stronger enough as reducing agent to reduce 
 a double bond unlike 
 which can reduce both the double bond and the carbonyl group.
       Activity 5.5 

 Process of alcoholic fermentation       

d. From esters

Esters on hydrolysis in the presence of mineral acid or alkalis produce alcohols and 

carboxylic acids.

    
Note:
           group followed by hydrolysis.

e. From Grignard reagents

The reaction between carbonyl compound and Grignard reagent (alkyl magnesium 
halides) produces an alcohol with more carbon atoms. The reaction is a nucleophilic 

addition on a carbonyl compound.

      

         

f. From primary amine to give primary alcohol

Primary amines react with nitrous acid to produce primary alcohols. 

       

Checking up 5.4

1. Using chemical equations, explain how 3-methylbutan-2-ol could be 
      prepared: 
   a. from an alkene
   b. using a Grignard reagent
   c. from a halogenoalkanes
   d. from an amine

   e. by reduction of a carbonyl compound

5.5. Preparation of ethanol by fermentation

     Activity 5.5 

   Process of alcoholic fermentation

        

6. Observe the above pictures and then interpret each picture. 
7. Describe the process followed to produce alcohol refer to the above 
     pictures. 
a. What are the raw materials used in the process? 
b. What is the main component of the final products? 
c. Give the name of the process illustrated by the picture

d. Propose another process that can be used to yield the product in b.

This method is mainly used to prepare ethanol industrially. Ethanol is prepared from 
starch (e.g. maize, cassava, millet, sorghum) and sugar (e.g. banana juice, molasses) 
by fermentation process.

Fermentation can be defined as any of many anaerobic biochemical reactions 
in which enzymes produced by microorganisms catalyse the conversion of one 

substance into another.

Alcoholic fermentation is the process in which enzymes act on carbohydrates to 
give simpler compounds like ethanol (alcohol) and carbon dioxide 

a. From starch
 malt obtained either from maize grain, millet, or cassava contains an enzyme called 

diastase which catalyzes the hydrolysis of starch to maltose.

           

At room temperature, yeast is added and one of its enzymes called maltase catalyzes 

the hydrolysis of maltose to simple sugar so called glucose.

      

Finally another enzyme of yeast called zymase catalyzes the decomposition of 

glucose to ethanol.

            

b. From sugar 

Molasses containing sugars are mixed with water and yeast and then allowed to 
ferment for several days after which ethanol are obtained during fermentation 
process.

One enzyme of the yeast called sucrase catalyzes the hydrolysis of sucrose present 

in the molasses to glucose and fructose.

            

Thus, another enzyme of yeast called zymase catalyzes 

the decomposition of glucose to ethanol.

          

The ethanol obtained by fermentation process is only about 11%. This is made 
concentrated by distillation which converts it to about 95% ethanol. This on further 
distillation yields a constant boiling mixture whose composition does not change 
(an azeotropic mixture). 

Therefore, 100% ethanol is obtained by either:
i. Adding quick lime which removes water
ii. Distilling with of benzene as a third component

Note: Methanol can be prepared industrially by the reaction of carbon monoxide 
and hydrogen at 300 °C and a pressure of 200 atmospheres.

             

Checking up 5.5
1. Briefly, describe the preparation of ethanol by alcoholic fermentation.
2. Compare and contrast the preparation of ethanol by hydration of ethene 

and by alcoholic fermentation.

Project work 5.1
The task is about the fermentation of glucose
Part A
In this project, you will investigate the fermentation of different types of 
substances containing starch. 
Requirements 
• Conical flask, 
• some yeast, 
• some boiled potatoes, 
• some bread, 
• some boiled cassava, 
• boiling tube, 
• cork with delivery tubes, 
• stands and cramps, 
• glucose, 

• weighing balance

Why boiled potatoes or cassava is preferred?
Procedure
Weigh 25g of each starch including glucose and place them in separate conical 
flasks. Add to each one spatula of dried yeast followed by 100 cm3
 of water.

Cork the conical flask and connect it to boiling tube containing lime water as 
shown in the figure below. Label each flask clearly. Leave all the flasks in a warm 
environment. Record your observation for seven days.
c. The conical flask
d. The boiling tube

For each type of starch

                         

Note: use the same quantity and concentration of lime water in each boiling 
tube.
Part B: Comparison of yield of alcohol obtained

 Filter the mixture from each flask separately and collect the filtrate in measuring 
cylinder. Record the volume in each case. Perform fractional distillation on each 
filtrate, collecting the fraction between  Record the volume of 
distillate collected from each starch.
Take  of each on watch glass, ignite and note the time it takes to burn completely.
Observe the amount of water left on watch glass.

5.6. Chemical properties of alcohols

Activity 5.6.1.
To investigate the oxidation reaction of an alcohol.
Requirements: methanol, ethanol, 2M sulphuric acid, potassium dichromate 
solution, test tubes, burner, droppers, propan-2-ol and 2-methylpropan-2-ol.

Procedure: 
• Place 5 drops of methanol in test tube
• Add 10 drops of dilute sulphuric acid followed by 5 drops of potassium 
  dichromate solution.
• Warm the mixture gently
• Repeat the experiment with ethanol, propan-2-ol and 2-methylpropan-2-ol.
     1. What happens to the colour of the solution?
    2. Explain the observation.

    3. Write an equation for the reaction taking place.

5.6.1. Oxidation

Primary and secondary alcohols are oxidized to aldehydes and ketones respectively 

by use of acidified. nitric acid once concentrated.

                    

             

Aldehydes formed by oxidation of primary alcohols tend to undergo further 

oxidation to carboxylic acid.

 Ketones formed by oxidation of secondary alcohols are not further oxidized, unless 
if the oxidizing agent is hot and concentrated in which case bonds around the –
CO_ group are broken and two smaller carboxylic acids are formed.

          

Tertiary alcohols resist oxidation because they have no hydrogen atom attached on 
the functional carbon atom. Oxidation also occurs when the alcohol is in gaseous 
phase by used of silver or copper catalyst under 500 °C and 300 °C respectively;
and the vapour of the alcohol is passed with air (oxygen) over heated silver.

Example 

These reactions help to distinguish between primary, secondary and tertiary 
alcohols because primary and secondary alcohols decolourise the purple 

solution of 

An acidified potassium dichromate solution is turned from orange to green when it 

reacts with primary and secondary alcohols. 

Secondary alcohols having the following structure only undergo 
oxidation, on treatment with iodine solution in the presence of sodium hydroxide to 

give yellow precipitate of tri-iodomethane.

Note: This is a reaction which is characteristic of methyl ketones, but
iodine here acting as an oxidizing agent first oxidizes the 
then the methyl ketone formed then gives the yellow precipitate of (Iodoform).

From the reaction involved we have the Iodoform test.

      

           

5.6.2. Reaction with sulphuric acid 

Activity 5.6.2

Show the product of the reaction referring to the preparation of alkenes and 

show the mechanism of reaction.

         

Alcohols react with concentrated acid to give products depending on the nature of 
the alcohol and conditions of reactions.
a. At about 0 °C alcohols react with sulphuric acid to produce alkyl hydrogen 

sulphates.     

       

This reaction is a substitution reaction where the OH group has been replaced by
b. At about 140°C in the presence of excess primary alcohol and concentrated 

sulphuric acid, ether is formed.

         

    

    Mechanism 

               

This reaction is an intermolecular dehydration.

c. Elimination reaction
Alcohols are dehydrated by heating with concentrated sulphuric acid or phosphoric 
acid to alkenes. The ease of dehydration is in the order tertiary>secondary>primary’, 

this reaction is the intramolecular dehydration of water.

        

Notice: For primary alcohols any temperatures between
 is sufficient and the acid should be sufficiently concentrated. 

       

This dehydration respects Zaïtsev’s elimination law (see alkenes) reason why the 

hydration of butan-1-ol and butan-2-ol gives the same products which is but-2-ene via

Elimination always competes with nucleophilic substitution reaction. Substitution 
leading to formation of ether is favoured by use of excess primary alcohols while 
higher temperatures favour elimination. Therefore, dehydration of ethanol may 
produce both alkenes by elimination and diethylether by substitution reaction. The 

relative proportion of two products depends on the condition of the reaction.

 

Dehydration of alcohols also occurs when the vapours of the alcohols are passed 
over heat aluminium oxide at about 300 °C.
              

5.6.3. Esterification
Alcohols react with organic acids in the presence of mineral acids lsuch as sulphuric 
acid (catalyst) with elimination of water under 100 °C to produce an ester with given 

off a perfume smell.

This reaction is called “esterification”.

    

          

The mechanism
Step 1
In the first step, the ethanoic acid takes a proton (a hydrogen ion) from the 
concentrated sulphuric acid. The proton becomes attached to one of the lone pairs 

on the oxygen which is double-bonded to the carbon.

        

Step 2

The positive charge on the carbon atom is attacked by one of the lone pairs on the 

oxygen of the ethanol molecule.

                                              

    Step 3

What happens next is that a proton (a hydrogen ion) gets transferred from the 
bottom oxygen atom to one of the others. It gets picked off by one of the other 
substances in the mixture (for example, by attaching to a lone pair on an unreacted 
ethanol molecule), and then dumped back onto one of the oxygens more or less at 

random.   

    The net effect is:  

                        

Step 4

Now a molecule of water is lost from the ion.

                

The product ion has been drawn in a shape to reflect the product which we are 

finally getting quite close to!

The structure for the latest ion is just like the one we discussed at length back in step 
1. The positive charge is actually delocalised all over that end of the ion, and there 
will also be contributions from structures where the charge is on the either of the 

oxygen atoms:

             

Step 5

The hydrogen is removed from the oxygen by reaction with the hydrogen
sulphate ion which was formed way back in the first step.

             

5.6.4. Reaction with strong electropositive metals and metal hydroxides

Electropositive metals like Na, K, react with alcohols forming alkoxide with 

evolution of hydrogen gas.

      

         

Note: Alcohols are not enough acidic to react with metal hydroxides such as 

sodium hydroxide or potassium hydroxide.

        

5.6.5 Action of hydrohalic acids (HX)

Activity 5.6.5

Referring to preparation of alkyl halides, complete the following reactions: 

       

Alcohols react with hydrohalicacids to give alkyl halides.

Examples 

         

      

Notice:
i. Reaction with concentrated hydrochloric acid is catalyzed by anhydrous 
    zinc chloride.
ii. This reaction is called LUCAS test and is used to distinguish between 
     simple primary, secondary or tertiary alcohols. In this reaction, the alcohol 

     is shaken with a solution of zinc chloride in concentrated hydrochloric acid.

Observations: Immediate cloudiness indicates presence of a tertiary alcohol. If the 
solution becomes cloudy within 5 minutes then the alcohol is a secondary one. 
Primary alcohol would show no cloudiness at room temperature since the reaction 

is very slow.

For example all alcohols which are isomers of can be distinguished by the 

LUCAS test.

Alcohols are also transformed into halogenoalkanes using phosphorus halides and 

thionyl chloride.

              

Checking up 5.6

1. An organic compound A possesses 87.6 % composition by mass and the 
rest is hydrogen. If the same molecule possesses the molecular mass of 
56 g/mol, deduce the molecular formula of A. 

a) The reaction of A with water produces the compound B. 
 B can be represented in different forms called isomers. Represent the 

 isomers of B.

When B reacts with it produces different compounds 
depending on the reaction conditions. Write the structural formulae of 
those compounds and state the conditions of their formation.
b) When B reacts withthree products are obtained depending on 

the temperature used. Write structural formulae of those products.

2. Explain why tertiary alcohols are not oxidized. 

3. Complete the following chemical reactions and name the products obtained:

                  

5.7. Uses of alcohols

Activity 5.7

In Rwnda, different types of alcoholic drinks are produced. However, some of 
the them produced locally including “Kanyanga” are prohibited.

a. Explain why this alcohols is prohibited?
b. Discuss the possible effects of using non certified alcoholic drinks.
c. How would you differentiate alcoholic products from non-alcoholic 

    ones?

Ethanol is the alcohol found in alcoholic drinks. Alcoholic fermentation converts 
starch sugar into ethanol. For example grapes are used to produce wine, ripe banana 
to produce urwagwa, honey for spirits are obtained by distilling the ethanol –water 
product obtained when sugar is fermented.

Drinking alcohol, i.e. the ethylic alcohol also called ethanol, is a normal social activity; 
but excess of it is dangerous for our health. Hence excess of alcoholic consumption 
must be avoided. For non-adult youth, consumption of alcohol in any form is illegal 

in Rwanda and many other countries.

There are some alcoholic drinks produced in Rwanda and in the Region that are 
prohibited to be sold in Rwanda. However, alcohols have many other applications in 

daily life as indicated in the Table 5.1. 

                                 Table 5.1. Application of some alcohols

           

           

Ethanol produced by sugar cane fermentation has been used as alternative fuel to 

gasoline (petrol). It has been mixed with gasoline to produce gasohol.

Project 5.2. USE OF ALCOHOLS

Consult leader to your community religious, political, professionals, e.g.
doctors, nurses, parents, teachers, and elders and find out from them the 

following:

• What are the true recommended users of alcohols
• How should alcohol be used
• Real life examples of the effect of alcohol abuse on:
i. Social life
ii. Spiritual life
iii. Physical life of an individual

a. Come up with your own resolution and statements concerning alcohol 
     abuse. Write it out on a card and share it with trusted friends and your 
     parents/guardian and mentor.

b. Discuss with your peers show how you would help one of your members 
    of your family who is addicted to alcohol to come out of it

c. Find out the good economic uses of alcohol.

5.8. Ethers

5.8.1 Structure and isomerism

 Activity 5.8.1.

1. Represent the possible isomers of Which of them are:
a. Structural isomers?
b. Functional isomers 

2. What homologous series do those isomers belong to? 

Ethers are organic compounds in which two carbon groups are connected to a 
single oxygen. The general formula of ether is R-O-R’. Based on the general structure 

of ether, they are classified as symmetrical, unsymmetrical and epoxide.

- For symmetrical esthers, R and R’ are identical

        

    - For unsymmetrical esthers, R and R’ are different (R#R’)

         

    - Cyclic ethers

         

   Checking up 5.8.

Classify the isomers of the molecules identified in activity 5.8.1 above into 

symmetric, asymmetric and cyclic.

5.8.2. Physical properties

1. Ethers are sparingly soluble in water but are soluble in organic solvents.
2. The polar nature of the C-O bond (due to the electronegativity difference of 
    the atoms) results in intermolecular dipole-dipole interactions.
3. An ether cannot form hydrogen bonds with other ether molecules since 
     there is no H to be donated (no -OH group).
4. Their melting and boiling points increase with the increase in molecular 
     mass because of increasing the magnitude of Van der Waal’s forces with size.
5. The boiling points of ethers are much lower than those of alcohols of similar 
     molecular mass. This is because of the intermolecular hydrogen bonding 

     which are present in alcohols but are not possible in ethers.

           

5.8.3 Preparation of ethers

 Activity 5.8.2 

1. With reference to alcohols, define intermolecular dehydration reaction. 
2. State the reagent and conditions used in that reaction and give one 

     example

1) Intermolecular dehydration of alcohols
This is done by heating excess primary alcohol with concentrated sulphuric acid or 

phosphoric acid at about 140˚C.

     

2) From halogenoalkanes

(a) In this method halogenoalkanes are heated together with sodium or potassium 

alkoxides.

              

           This is the Williamson’s synthesis

(b) In the second method, the halogenoalkane is heated with dry silver oxide.

                 

              

        5.9. Chemical properties of ethers

                  Activity 5.9

A compound with molecular formula  has three isomers. One of them

does not react with sodium metal. Identify that isomer.

Since they are saturated compounds and non-polar, they are relatively chemically 

inert reason why their chemical reactions are very few.

5.9.1. Reactions in which the carbon – oxygen bond is broken

    a. Ethers react with hot concentrated sulphuric acid to form alcohols according

         to the following reaction.

              

     

     b. Reaction with hydrohalic acids

            

     

     Ethers react with cold hydrohalic acids to form alkyl halides and alcohols. 

      R-O-R’ + HX→ ROH +R’X (cold)

          

      Note: For unsymmetrical ethers, the halogen is attached to the smaller of the two 

                   alkyl groups.

                 

                Ethers react with hot hydrohalic acids to form only alkyl halides.

             

a. Ethers can act as the Lewis base due to the two non-bonded electron pair on 
oxygen to form coordinative bonds with Grignard reagent. This explains clearly why 
organ magnesium compounds are manipulated in ether solvent but not in water 

since in water, there is a reaction which generate alkanes.

                               

b. Combustion of ethers gives carbon dioxide and water: 

          

5.9.2 Oxidation reaction

  Ethers react with oxygen of air to form peroxides 
 (less volatile than the parent ether)

In concentrated or solid form, these peroxides are dangerous because they are 
highly explosive. The presence of peroxides contaminates the ether. This type of 
contamination is purified by treatment with a reducing agent such as alkaline 

ferrous sulphate.

5.10. Uses of ethers

Activity 5.10

 A nurse is injecting anaesthesia to a patient as seen by the image below. 

                     

1. What product that form the anaesthesia.
2. Explain the effects of anaesthesia.

3. In which case a patient is injected anaesthesia?

Lower ethers are used as anesthesia since they produce inert local cooling when 
sprayed on a skin, ether are also used as local anesthesia for minor surgery operation.
Lower ethers are volatile liquid which on evaporation produce low temperature they 

are therefore used as refrigerants.

Ether itself is one of the most important organic solvents for fats, oils, resins, and 

alkaloids.

Checking up 5.10: 

Make a research and establish at least four uses of ethers

5.11. End unit assessment 

I. Multiple choice questions
1. What is the correct name of the molecule with the skeletal formula shown 

     below?

                   

A . 1,2, 2-trimethylbutan-3-ol
B. 2-ethyl-2-methylbutan-2-ol
C. 3,3-dimethylpentan-2-ol

D. 4-hydroxy-3,3-dimethylpentane

2. Compound X, C4H8O2, has an unbranched carbon chain. An aqueous 
solution of X has an approximate pH of 3. Compound Y, C3H8O, is a 
secondary alcohol. X and Y are reacted together in the presence of 
a little concentrated sulphuric acid to form Z as the major organic 

product.

    What is the structural formula of Z?

             

3. The ester CH3CH2CH2CO2CH2CH (CH3)2 was hydrolyzed under 
     acidic conditions.
     What are the organic products of this hydrolysis?
A. butanoic acid and 2-methylpropan-1-ol
B. butanoic acid and 2-methylpropan-2-ol
C. butan-1-ol and 2-methylpropanoic acid
D. propanoic acid and 2-methylpropan-1-ol

4. An unknown organic compound reacts with sodium to give a 
     combustible gas as one product but does not give a yellow precipitate 
     with alkaline aqueous iodine. What is a possible identity of the 
      unknown organic compound?
A. Propanol
B. Propan-1-ol

C. propan-2-ol

II. Open questions

5. A compound A   is found to be soluble in sulphuric acid, A doesn’t react 
    with sodium or potassium permanganate. When A is heated with hydroiodic 
   acid, it is converted into single alkyl iodide suggest the structure of A

6. An organic compound Y possesses the centesimal composition by mass 
   of 87.6% carbon and the rest is hydrogen. The molecular mass of it is 56 g/ 
  mol. Water molecule in presence of sulphuric acid was added to the same 
  molecule to produce M, the molecule M was subjected to sulphuric acid and 
  the temperatures of 140 °C, and produce N. Y possess many isomers including 
cycles molecules. 

Establish the structure of Y, and all isomers, M and all isomers and N. Show the 
mechanism where is possible.

7. An organic liquid M contains carbon, hydrogen and oxygen. When 0.25 g of M
     is combusted, 0.592g of carbon dioxide and 0.30 g of water was formed 
a. i. calculate the empirical formula 
    ii. Molecular formula if the molecular mass is 74 g/mol
b. Write the structural formula and name of all isomers of M
c. M gives a yellow precipitate with solution of iodine in sodium hydroxide

 i. Identify
ii. Describe briefly how the functional group in M may be determined 
iii. Give a reaction scheme of how M can be converted into but-2-yne 

8. Compare and contrast the preparation of ethanol by hydration of ethanol and 
    by fermentation by putting an emphasis on the advantages and disadvantages 

    of each process.