Jay-Z Draw the MOP for the following: DCI -30°C MOP A DCI -30°C same chemical reactivity since MOP B both are hydrogens H =
H (protium) D =
H (deuterium) (only difference is in rate) Unlike the protium isotope of hydrogen (symbol H), deuterium is NOT understood and must be shown. Use the X-tool on JME toolbar to input D.
Jay-Z Draw the MOP for the following: DCI -30°C MOP A DCI -30°C same chemical reactivity since MOP B both are hydrogens H =
H (protium) D =
H (deuterium) (only difference is in rate) Unlike the protium isotope of hydrogen (symbol H), deuterium is NOT understood and must be shown. Use the X-tool on JME toolbar to input D.
The Correct Answer and Explanation is:
To properly address your question, let’s break it into its chemical context and what is expected.
Correct Answer: MOP A and MOP B for DCI at -30°C
You are being asked to draw the Mechanism of Product formation (MOP) for a molecule called DCI, where:
- D = Deuterium (²H), an isotope of hydrogen
- C = Carbon
- I = Iodine
This likely refers to Deuterochloro-iodomethane or a similar compound undergoing a reaction at -30°C. You are asked to draw MOP A and MOP B, where:
- MOP A: DCI reacts with a protium (H) source
- MOP B: DCI reacts with a deuterium (D) source
Both MOPs have the same chemical reactivity, but the only difference is in rate of reaction, due to the isotopic substitution (H vs. D).
This means the reaction likely involves C-H or C-D bond cleavage, and you’re observing the Kinetic Isotope Effect (KIE).
Explanation
The Mechanism of Product (MOP) formation for DCI at –30°C involves a substitution or elimination reaction pathway where the C–H or C–D bond breaks. Deuterium (D) is an isotope of hydrogen with one neutron in addition to the proton, making it heavier than protium (H). Despite having nearly identical chemical properties, reactions involving D–C bonds typically proceed more slowly than those involving H–C bonds due to the Primary Kinetic Isotope Effect.
In MOP A, where DCI reacts in the presence of H (protium), the C–D bond remains intact, and the lighter H reacts or is involved in the transition state. In MOP B, where DCI reacts in the presence of D (deuterium), the breaking or forming of a C–D bond occurs, which requires more energy and thus slows the reaction rate.
This means both mechanisms are chemically identical, involving the same intermediates and transition states, but MOP A proceeds faster due to the lower bond dissociation energy of the C–H bond compared to the C–D bond.
From a mechanistic perspective, this difference doesn’t result in different products, but does affect the reaction kinetics. It’s important to use the “X” tool in the JME Molecular Editor to explicitly indicate deuterium (D), as it’s not assumed like H.
This concept is widely used in mechanistic studies to determine which bonds are broken in the rate-determining step of a reaction. Therefore, understanding the role of isotopes like D in MOPs provides crucial insight into reaction pathways and transition state dynamics.
