The isotope of hydrogen with mass number 2 is called Deuterium (D). The C―D bond is slightly stronger than the C―H bond and because of this, reaction rates tend to be slower when a C―D bond is broken in a rate-limiting step compared to a C―H. This effect, called a kinetic isotope effect, is observed in the comparison of the bromination of methane and tetradeuteriomethane. Provide the transition state for the rate-limiting step of each of these reactions.

• A.
• B.
• C.
• D.

Answer: (C)