1. Pyrolysis is defined as the thermal decomposition of an organic compound into smaller fragments in the absence of air through the application of heat. Pyrolysis of alkanes is also named as cracking.
2. In the absence of air, whai alkane are vapours passed through red-hot metal it breaks into simpler hydrocarbons.
(a) CH3 - CH2 - CH3 (Propane) \(\overset {773K}{\longrightarrow}\) CH3 - CH = CH2(propane) + CH2 = CH2 (Ethylene) + H2 + CH4(Methane)
(b) 2CH3 - CH3 (Ethane) \(\overset {773K}{\longrightarrow}\) CH2 = CH2 (Ethane) + 2CH4 (Methane)
3. The product depends upon the nature of alkane, temperature, pressure and presence or absence of the catalyst.