6. Thermodynamics and Kinetics
Energy Diagram
32PRACTICE PROBLEM
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.
![](https://lightcat-files.s3.amazonaws.com/problem_images/7cbb7b34558fff60-1713288388649.jpg)
In another reaction, the monobromination of deuterioethane (C2H5D) yields a mixture of C2H5Br and C2H4DBr in a 1:10 ratio. Calculate the relative rate of abstraction of H to D.
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.
In another reaction, the monobromination of deuterioethane (C2H5D) yields a mixture of C2H5Br and C2H4DBr in a 1:10 ratio. Calculate the relative rate of abstraction of H to D.