• AHMAD TAKALLOU

      Articles written in Journal of Chemical Sciences

    • Fluxional nature in cyclohexane and cyclopentane: spherical conformational landscape model revisited

      SAHAR SAKHAEE MOHAMMAD HOSSEIN SAKHAEE AHMAD TAKALLOU FATEMEH FOROUZANFAR NADER SAKHAEE

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      Spherical conformational landscape model was revisited to include yet another class of cyclic compounds; the derivatives of cyclohexane. The updated model is not only capable of explaining Raman spectral features in fluxional cyclopentane but is also capable of revealing similarities between cyclopentane and cyclohexane derivatives for the first time. At the heart of the model lies the aspect of B/T ring coordinates (B/T conformational platform) that represents different levels of puckering (q). DFT-wb97xd/6-311 + G* computations confirmed by MP2/aug cc-pVTZ computations were used to fully investigate 16 differentderivatives of both cyclohexane and cyclopentane. Intrinsic reaction coordinate, IRC, computations were performed to gain insight into patterned inter-platform pathways connecting ring coordinates. These pathways revealed the coupling strength between bent/boat, B, and twist, T, ring coordinates. The coupling is found to be stronger for cyclopentane compared to cyclohexane. Some spectral features in the overlap region near 1400 cm-1 show promising signs on spin–spin relaxation, T2, mechanism. The work opens up an avenue for conformational studies of medium-sized rings. Also, ongoing studies to unravel potential relationships between conformational flexibility and bioactivity of cyclic compounds are underway.

    • Mechanistic pathways for halogen dance reactions in bromothiophenes: a cascade-like pattern

      NADER SAKHAEE SAHAR SAKHAEE AKBAR MOBARAKI AHMAD TAKALLOU MOHAMMAD HOSSEIN SAKHAEE

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      Ever since the halogen dance reaction was discovered by Bunnet et al, synthetic chemists have utilized the transformation in many desirable ways to build substituted heterocyclic target molecules of all kind. Using DFT-Cam-B3LYP/ land2dz computations and focused on Hannes Frohlich et al. Halogen Dance(HD) reactions of bromothiophenes, a new bromo-bridged Transition State (TS) is proposed. This bromobridged TS was then used to put forth eight possible isomerization as well as eight possible disproportionation paths. These mechanistic pathways were then carefully inspected based on TS’s energy and protonation/deprotonation steps to find the most suitable pathways. Collectively these mechanistic pathways joined like a jigsaw puzzle to give, for the first-time, a fully comprehensive cascade-like pattern for base-catalyzed halogen dance in its entirety. The present work may well shed light on a dynamic domino mechanism which dominates the realm of nonaqueous strongly basic medium, organic chemistry, reactions

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