The kinetics of the title reaction were studied in toluene at 80 °C by means of HPLC. The overall rate constant (ktotal) of the reaction of (E)‐β‐nitrostyrene (1) with (Z)‐C‐phenyl‐N‐arylnitrones (2a–g) was found to increase with increasing Hammett σ‐constant, whereas in the case of (Z)‐C‐aryl‐N‐phenylnitrones (2g–p) and the same nitrostyrene the rate decreased. The substituent effect in these reactions is inconsistent with FMO treatments of cycloaddition rates. For both reaction series good linear relationships were obtained between log ktotal and the net charge on the carbon atom in the >CN(O)— moiety of the nitrones calculated by the AM1 method. Copyright © 2001 John Wiley & Sons, Ltd.