WAEC Standard for Answering Organic Chemistry

State two advantages of synthetic polymers over natural polymers.

The expected answers include: – cheaper
– more durable
– can be recycled
– easily moulded
– lighter
– can be made on demand / tailor made
– easily available
– can be produced in larger quantity
– can be formed fasterDraw the structure of the product formed when one mole of ethyne reacts with two moles of hydrogen bromide and name the product(s).

The product formed is dibromoethene

Explain briefly why benzene is soluble in ethanol but insoluble in water

Benzene and ethanol are organic compounds while water is an inorganic / polar compound / like dissolves like / organic compounds dissolve in organic solvents hence benzene is insoluble in water.

Give the reagent(s) that could be used to distinguish between each of the following pairs of compounds.
I. CH3(CH2)2CH2OH and CH3CH2OH
II. CH3CH2C =CH and CH3C = CCH3

i. KMnO4 / I2 / NaOH
II. NH3 / AgNO3 // NH3/ CuCl
III. Br2 / CCl4 // H+/ KMnO4 // H+ / K2 Cr2 O7, Bromine water (i)

Consider the compound below. CH3CONH2CH2OH (i) Draw the structure of the compound.
(ii) Name the functional group(s) present in the compound.

(ii) – Amide
– hydroxyl / hydroxy

Give the names of the following compounds:
(i)         CH3CH=CHCH2CH3;
(ii)        CH3CH2CH2-C-OH.

(i)     2 – pentene/ pent -2- ene
(ii) Butanoic acid

Consider the following compounds:
            CH3CH=CHCH3; CH3COOCH2CH3; CH3(CH2)2CH3 and CH3CH(OH)CH2CH3

  1. State the family to which each organic compound belongs.
  2. Give the IUPAC name of each compound.
  3. Arrange the compounds in order of increasing boiling point.

Give reasons for your answer     

  1. CH3CH =CHCH3 – Alkene
    CH3COOCH2CH3 – Alkyl alkanoate
    CH3(CH2)2CH3 – Alkane                  
    CH3CH(OH)CH2CH3 – Alkanol.

2. CH3CH=CHCH3           –           But–2–ene / 2 – butane
CH3COOCH2CH3      –           Ethyl ethanoate
CH3(CH2)CH3             –           Butane            
CH3CH(OH)CH2CH3 –           Butan–2–o1

(iii)       CH3(CH2)CH3< CH3CH = CHCH3< CH3COOCH2CH3
The stronger the forces, the higher the boiling point
Vander waals forces exist in CH3CH=CHCH3 and CH3(CH2)2CH3
Dipole – dipole interaction exist in CH3COOCH2CH3
Hydrogen bonding exits in the alkanol.

(c)     Ethanol is produced on a large scale by heating ethane with steam.

  1. State two other conditions necessary for the reaction.
  2. Write the balanced chemical equation for the reaction.
  3. State one advantage of this method over the fermentation method.
  1. – High pressure    
    – Acid catalyst OR Conc. H2SO4/H3PO3

            2     . C2 H4 + H2SO4       C2 H5 HSO4
C2H5HSO4+H2O         C2H5OH + H2SO4
C2H4 + H2O  CH3CH2OH

     3. –     Faster reaction
–           Continuous reaction
–           Pure production/concentrated product
–           Does not produce CO2 or green house gas/environmentally friendly