Rovibrational NMR isotope effects

The second kind of NMR isotope effect has its origin in the mass differences between isotopes. In NMR mass effects show up as isotopic differences in NMR shielding constants and coupling constants. Their theoretical rationalization is 

A second example of a study exploiting chemical shift isotope effects is shown in Fig. 7.15b which reports 1II, 2H and 19F low temperature NMR spectra of the 

As an example of this technique we consider 12C/13C isotope effects in the Diels-Alder condensation of isoprene and maleic anhydride (Equation 7.32). The terminal carbons of isoprene carbons are numbered 1 and 4, the methyl substituted carbon is number 2. The reaction proceeds via a concerted and slightly asynchronous mechanism. 

Carbon atom Isotope fractionation k(12C)/k(13C) from Equation 7.23 

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