(a) ethane from ethene
When ethene reacts with hydrogen in the presence of Ni at 250 to 300 °C ethane is formed.
Ni
H2C=CH2 + H2 H3C-CH3
250-300°C
(b) Acetylene from tetra-halide
When an alkyl tetra-halide is heated with zinc dust, the elimination of halogen atoms takes place and acetylene is formed.
Cl Cl
H-C―C-H +2Zn(dust) heat HC≡CH + 2ZnCI2 Cl
Cl Cl (Ethyne)
(c) Carbon tetra-chloride from methane
Alkanes react fairly with halogens in diffused sunlight only. CH4 reacts with Cl2 in diffused sun light to form chloromethane, dichloromethane tri chloromethane and finally Tetrachloromethane
diffused
CH4 + C12 CH3C1 + HC1
Sunlight Chloromethane
CH3C1 + C12 CH2C12 + HC1
Dichloromethane
CH2C12 + C12 CHCl3 + HCl
Trichloromethane
(Chloroform)
CHC13 + C12 CCl4 + HC1
Tetrachloromethane
(Carbon tetrachloride)
(d) Ethylene glycol from ethene
When ethene is treated with aq. alkaline KMn04 solution, ethylene glycol is formed in cold state.
3CH2 = CH2 + 2KMnO4 + 4H2O 3CH2 ― CH2 + 2KMnO4 + 2KOH
(e) 1,2-dibromoethane from ethene
When ethene is treated with bromine 1, 2-dibromoethane is formed.
H2C=CH2 + Br2 + Br-CH2-CH2-Br
(f) glyoxal from acetylene
When acetylene is oxidized by alkaline KMn04 hydroxyl groups add to triple bond. This intermediate product eliminates water molecules to form glyoxal.
HC≡CH + 2KMnO + 2H20 OH OH + 2MnO2 + 2KOH
H-C—C-H
OH OH
O O
OH OH -2H2O ║ ║
H-C—C-H H-C-C-H
OH OH Glyoxal