Chapter 12, Problem 90AE

Iodomethane (CH₃I) is a commonly used reagent in organic chemistry. When used properly, this reagent allows chemists to introduce methyl groups in many different useful applications. The chemical does pose a risk as a carcinogen, possibly owing to iodomethane’s ability to react with portions of the DNA strand (if they were to come in contact). Consider the following hypothetical initial rates data:

[DNA]0 (μ mol/L)	[CH3I]0 (μ mol/L)	Initial Rate (μmol/L·s)
0.100	0.100	3.20 × 10−4
0.100	0.200	6.40 × 10−4
0.200	0.200	1.28 × 10−3

Which of the following could be a possible mechanism to explain the initial rate data?

$\begin{array}{lll}\text{Mechanism}\text{I}\hfill & {\text{DNA+CH}}_{\text{3}}\text{I}\hfill & \to \text{DNA}—{\text{CH}}_{\text{3}}{}^{+}+{\text{I}}^{-}\hfill \\ \text{Mechanism}\text{II}\hfill & {\text{CH}}_{\text{3}}\text{I}\hfill & \to {\text{CH}}_{\text{3}}{}^{+}+{\text{I}}^{-}Slow\hfill \\ \hfill & {\text{DNA+CH}}_{\text{3}}{}^{+}\hfill & \to \text{DNA}—{\text{CH}}_{\text{3}}{}^{+}Fast\hfill \end{array}$