Orientation of reactant molecules

The requirement for a successful collision described above is sufficient for reactions involving simple molecules (or ions), however not for those involving complex molecules.

Besides the above considerations, the colliding molecules must have the proper orientation: the molecules need to be so oriented relative to each other that the reacting groups approach closely.

Consider, $\mathrm{A + C\text{-}B \longrightarrow A\text{-}B + C}$

i. The collision of A with C approaching toward A would not lead to reaction.

No reaction will take place: the reactant molecules would collide and separate, owing to the improper orientation of C - B.

ii.

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