Abstract: An approximation approach for evaluating rate constants from a single 2D exchange spectrum is proposed, based on theoretical analysis of the amplitude of 2D peaks. For sufficiently short mixing time τ_m, the magnetization transfer can be seen as single-direction-transfer from the diagonal peak to cross peak(s). The expressions of the amplitude as a function of τ_m are presented. The results are in agreement with that of Ernst theory within the first order approximation, but differs a little bit in the second order approximation. However, the problem has been much simplified, and the results coincide with the recently obtained ¹¹⁹Sn 2D exchange spectrum of SnCl₆^2- hydrolyzing system quite well. Thus the exchange rate constants for this system are evaluated directly by the simple method.

Key words: ¹¹⁹Sn NMR, Two-dimensional exchange spectroscopy, SnCl₆^2-, Hydrolysis, Rale constants