Question

For the reaction, R – X + OH^–¾® R OH + X^–, the rate of overall reaction is given by,

Rate = 5 × 10^–5 [R – X] [OH^–] + 2 × 10^–6 [R – X]

When concentration of OH^– is 10^–2 (M), then what percentage of R – X react by SN²mechanism?

• A. 96.1 %
• B. 3.9 %
• C. 80 %
• D. 20 %

Answer 1

Answer: (D)

20 %

Answer 2

The SN² reaction rate = 5 × 10^–7 [R – X]

The SN¹ reaction rate = 20 × 10^–7 [R – X]

\ % of SN² reaction = $\frac{5 \times 10^{- 7}}{25 \times 10^{- 7}}$ × 100 = 20%