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Author: search.filters.author.Roy, Ram KinkarSubject: search.filters.subject.Energy

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    A comprehensive decomposition analysis of stabilization energy (CDASE) and its application in locating the rate-determining step of multi-step reactions
    (RSC, 2009) Roy, Ram Kinkar
    Stabilization energy, as proposed by Parr and Pearson (J. Am. Chem. Soc., 1983, 105, 7512) is decomposed into fragments. When the donor is not a perfect one and both the donor and the acceptor are ordinary organic molecules this decomposition is shown to provide energy fragments which, individually, can be correlated to the reaction rate of that particular step. It is shown how these different energy fragments can be used, together with the global electrophilicity value of the acceptor (wA), to locate the rate-determining step in multi-step reactions.
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    Interaction between Small Gold Clusters and Nucleobases: A Density Functional Reactivity Theory Based Study
    (ACS, 2015) Roy, Ram Kinkar
    The thermodynamic and kinetic aspects associated with the interaction of small gold clusters (Aun, where n = 3–6) with nucleobases are assessed using a density functional reactivity theory based comprehensive decomposition analysis of stabilization energy scheme. It is observed that the trend of interaction between Aun clusters and nucleobases follows the order G > A > C > T > U. Also, the Watson–Crick base pair GC interacts with Aun clusters more preferably than that of the AT pair. The observed trend is further supported by conventional binding energy and transition-state calculations at B3PW91 and MP2 levels.
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    Solvent effect on stabilization energy: An approach based on density functional reactivity theory
    (Wiley, 2019-03-02) Roy, Ram Kinkar
    In the present article a formalism and the corresponding computational method is developed to take care of the variation of stabilization energy with solvent polarity in the process of adduct formation. For this purpose, a simple but physically insightful definition of “net desolvation energy” is proposed keeping in mind the sequence of events taking place in the process of adduct formation in a solvent. The approach used here is based on density functional reactivity theory (DFRT) and the representative samples chosen are adduct formation between (a) methyltrioxorhenium (MTO) and pyridine and (b) (azidomethyl)benzene and methylpropiolate. The generated data in case (a) is correlated with already known experimental parameter that is, formation constant (Kf). The observed trends claim that with the increase in solvent polarity interaction (or stabilization) energy becomes less negative which means that on increasing the solvent polarity the chances of adduct formation are less. This is further supported by calculating hardness values of adducts in different solvents which goes on decreasing with the increase in solvent polarity. Here, the computed data show that on increasing the polarity (i.e., dielectric constant) of the solvent, the “net desolvation energy” increases. Finally, when “net desolvation energy” is added to the stabilization energy obtained from DFRT the predicted trends are achieved.
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    Correlation between Equilibrium Constant and Stabilization Energy: A Combined Approach Based on Chemical Thermodynamics, Statistical Thermodynamics, and Density Functional Reactivity Theory
    (ACS, 2020-01-21) Roy, Ram Kinkar
    In the present work, an attempt is made to establish the correlation between equilibrium constant and stabilization energy [ΔESE(AB)] generated from density functional reactivity theory (DFRT). The reactions chosen here are of type A + B ⇌ AB (i.e., adduct formation type) between an electron acceptor, A, and an electron donor, B. The representative acceptors are methyltrioxorhenium (MTO) and substituted benzaldehydes whereas donors are 26 mono- and bidentate ligands (having N-donors) and semicarbazide. The trends of experimentally generated equilibrium constant (K) values match with those of ΔESE(AB) in most of the cases, both in gas phase as well as in solvent. Justification of this reliable correlation is provided analytically using the expressions of standard Gibbs free energy of reaction (i.e., ΔrGθ) and the stabilization energy expression generated by DFRT. A further analytical explanation (albeit not very rigorous) is provided through statistical thermodynamics showing how equilibrium constant (K) is related to ΔESE(AB) for reactions of the type A + B ⇌ AB, where either A or B is a common species.