<i>PeriRxn</i> , a Tool for Assessing Pericyclicity through Nucleus-Independent Chemical Shifts and Normalized Multicenter Bond Orders

Analyses of nucleus-independent chemical shifts (NICS) and normalized multicentered bond orders (nMCBO) along reaction coordinates were used to quantify the degree of cyclic delocalization occurring during various reactions as a criterion for determining whether reactions are pericyclic. The magnitude of the <i>z</i>-sampled average NICS, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover><mml:mrow><mml:msub><mml:mrow><mml:mi>NICS</mml:mi></mml:mrow><mml:mrow><mml:mi>z</mml:mi><mml:mi>z</mml:mi></mml:mrow></mml:msub><mml:mspace></mml:mspace></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:math>, and nMCBO near the transition structure were found to be good indicators of pericyclicity, but the topology of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover><mml:mrow><mml:msub><mml:mrow><mml:mi>NICS</mml:mi></mml:mrow><mml:mrow><mml:mi>z</mml:mi><mml:mi>z</mml:mi></mml:mrow></mml:msub><mml:mspace></mml:mspace></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:math> along the intrinsic reaction coordinate proved to be more informative.