Sulphonation:- replacement of hydrogen atom of alkane by – SO 3 H group.
CH3
CH CH3
CH3
isobutane
The reaction occurs as: HO-SO3 oleum
450 0 C Homolytic fission
CH3
C
CH3
SO3H
CH3
tert butyl sulphonic acid
HO o + o SO3H
Aromatization:-
RH + 0 OH R o + o SO2H
H3C( CH2) 3CH3 n-Pentane
H3C( CH2) 4CH3 Hexane
AlCl3 / HCl
Cr2O3
773 K 10-20 atm
R o + HOH RSO2H CH3
H3CCHCH2CH3 2-Methyl butane
Benzene
This method is also called dehydrogenation or hydroforming similarly, heptane gives toluene, n-Octane give o-xylene and 2, methyl heptane give m-xylene.
Thermal decomposition or Pyrolysis or cracking or Fragmentation:- when higher alkanes are heated at high temp( about 700-800k) in the presence of alumina or silica catalysts, the alkanes break down to lower alkanes and alkenes.
CH3-CH2-CH3
CH3-CH-CH2 + CH3-CH3 + C2H4 + CH4
Action of steam:- catalyst: nickel, alumina Al2O3
CH4 + H2O( Steam)
CO + 3H2
This reaction is used for the industrial preparation of hydrogen from natural gas. 8. Isomerization:-