Consider the following reaction

If `r_(1)` is the rate of reaction and `r_(2)` is the rate of racemisation then which of the following relation is true ?

Options

A. `r_(1)=r_(2)`
B. `r_(1)=2r_(2)`
C. `r_(2)=2r_(1)`
D. `r_(2)=4r_(1)`

Answer

C

Explanation

The above reaction follows `S_(N)2` path. The formation of product with radioactive iodine `(""^(131)I)` is a mirror image of the reactant. Thus, they are enantiomers of each other.
If 100 molecules of reactants are assumed to be taken, initially, then racemisation will be completed as soon as 50% of the molecules of the reactants are consumed. Thus, racemisation takes place at a double rate than of reaction. Thus, `r_(2)=2r_(1)`.