rate determination by 1H NMR spectroscopy

Question

Currently I investigate a reaction where a starting material A reacts with an excess of thiophenol B towards products C and D. As shown by recurrent TLC analysis of the reaction, the formation of D is slower than the one of C, while A and B are still detectable.

Perhaps the reactions are consecutive, i.e.

$\ce{A + B ->[k_1] C ->[k_2] D}$

or they are simultaneous, i.e.

$\ce{D <-[k_2] A + B ->[k_1] C}$.

A, B, C, and D are distinguishable by 1H NMR spectroscopy; NMR data of the purified compounds A, B, C, and D were recorded successfully.

Based on a recurrent 1H NMR spectroscopy, I would like to use the integrations of the signals to determine the rate constants; perhaps there is evidence for the first case (similar to Bodenstein principle). The advancement of the thioetherifications alter the multiplicities of the signals observed, and simultaneously indicator signals vanish.

Question: Prior to get work on my data, where may I find a tutorial of reactions with known starting material(s)/product(s), determined rate constant(s) and NMR data-used-to-determine-these-rate-constants?

Answer 1

As mentioned in the comments, J. Chem. Ed is a good resource for NMR kinetics experiments. I have had success with the experiment published by J. Orvis in J. Chem. Ed 80(7), 2003, 803 link. This publication describes the synthesis of trans-dichlorotetraamminecobalt(III) and its subsequent reaction with water to produce cis-aquachlorotetramminecobalt(III). There are several advantages to this experiment as a model study:

• The synthesis is straightforward and does not require materials unlikely to be already in the laboratory, although it is critical that the directions are followed precisely.
• The aquation reaction occurs within about one hour - slow enough to easily monitor via NMR but not so slow as to take up precious instrument time
• The reaction rate is temperature sensitive, which makes it a good model for extracting thermodynamic properties from the reaction

My undergraduate students are able to complete the synthesis about 50% of the time, and the yields using the published procedure are about 400 mg, so one successful synthesis is suitable for a number of NMR experiments.