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Wize University Chemistry Textbook > Organic Chemistry Reactions

Reactions of Alkanes

Electrophilic Aromatic SubstitutionPrevious Section
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Chain Reactions

  • A chain reaction is a reaction which, once initiated, proceeds extremely fast because each time a highly reactive intermediate reacts to form product it produces another equivalent of highly reactive intermediate.
  • Chain reactions can be split into three types of steps, Initiation, Propagation, and Termination. An example is shown below.
A2→2A∙InitiationA_2\to 2A \bullet \hspace{30pt} Initiation
Propogation={A∙+B2→AB+B∙B∙+A2→AB+A∙Propogation = \begin{cases} A\bullet +B_2 \to AB+B \bullet \\ B \bullet +A_2 \to AB +A \bullet\\ \end{cases}

Termination={2A∙→A22B∙+B2A∙+B∙→ABTermination = \begin{cases} 2A\bullet \to A2 \\ 2B \bullet +B2\\ A \bullet +B\bullet \to AB \end{cases}
  • Initiation produces the reactive intermediates (radicals)
  • Propagation consumes on radical and produces another one
  • Termination consumes two radicals and produces none
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Alkane Halogenation

  • Alkanes can be hydrogenated by activating halogens with either light or heat in the presence of alkanes.


Mechanism (A Chain Reaction):

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Predict the products of the following reactions


The reaction shown below is part of the alkane halogenation reaction. What type of step is it?