For a certain reaction,a large fraction of molecules has energy more than the threshold energy,yet the rate of reaction is very slow. Why?

(N/A) According to the collision theory,for a reaction to occur,two conditions must be met:
$1$. The colliding molecules must possess energy equal to or greater than the threshold energy $(E_t)$.
$2$. The colliding molecules must have a proper orientation during the collision.
Even if a large fraction of molecules possesses energy greater than the threshold energy,the reaction rate remains slow if the molecules do not collide with the correct orientation.
The rate of reaction is given by the equation: $\text{Rate} = P \cdot Z_{AB} \cdot e^{\frac{-E_a}{RT}}$,where $P$ is the steric factor (or probability factor) representing the fraction of collisions with proper orientation. If $P$ is very small,the reaction rate will be slow.