A theoretical study of the effects of polar substitution on the activation barriers for internal rotation around the C-N bond in p-substituted nitrosobenzenes: comparison of DFT and MP2 calculations

Authors: ŞAFAK ÖZHAN KOCAKAYA, NECMETTİN PİRİNÇÇİOĞLU

Abstract: The activation barriers for internal rotation around the C-N bond in p-substituted nitrosobenzenes were calculated using the density functional theory (DFT) and second-order Møller-Plesset (MP2) methods with the 6-31+g(d) basis set. The polarisable continuum model (PCM) was used to model the solvent effect. An explicit water molecule was also introduced to form a hydrogen bond with the nitrosogroup and its effect on the barrier was studied by DFT. The barriers were well-correlated with Hammett sigma^+ rather than sigma values, meaning a strong resonance effect. The MP2 method produces better and comparable results with the few available experimental values.

Keywords: Para-substituted nitrosobenzenes, C-N bond rotation, polar substituent effect, molecular modelling DFT, MP2, PCM.

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