Next, we computed fA values for the most stable isomers of III-Br and III-I, identified as products in R1 (Table ), to evaluate differences the in electronic density distribution within III-Br and III-I, leading to IV-Br and IV-I, respectively (Scheme 3). As per computed fA values, the most probable electrophilic sites for the surrounding electron density within III-Br appeared around the bromoalkyl chain tethered to the core pyrazolyl ring (fA + (Br) = 0.524, fA + (C) = 0.228, Scheme 3a). In contrast, the most probable electrophilic sites for the surrounding electron density within III-I appeared around the C4-I site of the pyrazolyl ring, indicating an Scheme 2. Chemical reactivities of I as deduced by Fukui Indices with nucleophilic sites (blue) and electrophilic sites (red) as listed in the parentheses. Free energies in kcal/mol for I are listed in parentheses. Specifically, the anticipated products, VIII-Br and VIII-I, resulted in a relatively lower energy barrier, respectively. However, the unexpected experimental reactivity of III-Br to form Py-N-ene was not explained by classical TST. Therefore, based on our electron density calculations (Scheme 3a), we computed a different low energy conformational isomer of III-Br in the absence of counter ions (Br -, Na + ), labeled as IX-Br (Fig. , Model 2), with a ∠C1C2C3C4 dihedral angle of 25.1 o . Subsequently, we predicted a chemically non-intuitive reaction route with IX-Br (R4, Scheme 5) which followed a series of fourmembered transition states (X-Br and XI-Br, Scheme 5), involving a structural shift of the nitrile group from an alpha site to a distant gamma site relative to the core pyrazolyl nitrogen, XII-Br, ultimately leading to a low energy product, XIII-Br that was identified experimentally.