text: The pyrolysis (thermal decomposition) of acetaldehyde, CHCHO (g) → CH (g) + CO (g), proceeds via the Rice-Herzfeld mechanism:
  *Initiation (formation of free radicals):
  : CHCHO (g) → •CH (g) + •CHO (g)	              k
  The methyl and CHO groups are free radicals.
  *Propagation (two steps):
  : •CH (g) + CHCHO (g) →  CH (g) + •CHCO (g)            	k
  This reaction step provides methane, which is one of the two main products.
  : •CHCO (g) → CO (g) + •CH (g)		        k
  The product  •CHCO (g) of the previous step gives rise to carbon monoxide (CO), which is the second main product.
  The sum of the two propagation steps corresponds to the overall reaction CHCHO (g) → CH (g) + CO (g), catalyzed by a methyl radical •CH.
  *Termination:
  : •CH (g) + •CH (g) → CH (g)              	k
  	This reaction is the only source of ethane (minor product) and it is concluded to be the main chain ending step.
  Although this mechanism explains the principal products, there are others that are formed in a minor degree, such as acetone (CHCOCH) and propanal (CHCHCHO).
  Applying the Steady State Approximation for the intermediate species CH(g) and CHCO(g), the rate law for the formation of methane and the order of reaction are found:
  The rate of formation of the product methane is
  For the intermediates
   and
  Adding (2) and (3), we obtain 
  so that 
  Using (4) in (1) gives the rate law , which is order 3/2 in the reactant CHCHO.