Among 160 organic NHx-containing compounds (x = 1, 2) detected in the atmosphere, there are about 80 species for which the molecules contain p-pi conjugate substructures of NHx-pi-bonds. Here, chlorine radical (center dot CI)-initiated reactions for formamide, N-methylformamide, ethenamine, and aniline, as their cases, were investigated by a quantum chemical method [CCSD(T)/aug-cc-pVTZ//MP2/631+G(3df,2p)] and kinetics modeling. The calculated overall rate constants are 5.5 X 10(-11), 2.3 X 10(-10), 2.7 x 10(-10), and 1.7 X 10-10 cm(3) molecule(-1) s(-1) for formamide, N-methylformamide, ethenamine, and aniline, respectively, and agree well with experimental values for available ones. Importantly, the results show that the reactions of two amides with center dot Cl mainly lead to amides. However, both ethenamine + center dot Cl and aniline + center dot CI reactions C-center radicals via center dot Cl abstracting the -CHO hydrogen of mainly produce delocalized radicals with the radical center on the C-site and N-site via a center dot Cl addition and the -NHx hydrogen abstraction pathway, respectively. Therefore, this study reveals that reactions of organic NH-containing compounds with center dot Cl have various reaction mechanisms, in contrast to our previous understanding that-NHx hydrogen abstraction pathways, leading to N-center radicals, are the most favorable. The unveiled reaction mechanisms should be of significance for the risk assessment of atmospheric organic NH-containing compounds and enriching center dot Cl chemistry.