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Radionuclide Production
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Water targets are in some labelling chemistry not the best choice. An alternative production route is to use neon gas, 20Ne(d,α)18F. Adding fluorine-19 gas to the neon as carrier will yield 18F2 that can be used for electrophilic substitution. However, adding carrier will lower the specific radioactivity of the labelled product.
A Computational Modeling of the Structure, Frontier Molecular Orbital (FMO) Analysis, and Global and Local Reactive Descriptors of a Phytochemical ‘Coumestrol’
Published in Nazmul Islam, Satya Bir Singh, Prabhat Ranjan, A. K. Haghi, Mathematics Applied to Engineering in Action, 2021
P. Vinduja, Vijisha K. Rajan, Swathi Krishna, K. Muraleedharan
The electrophilicity is used for the description of reactivity that allows a quantitative classification of the global electrophilic nature of a molecule within a relative scale. Electrons flow from places with higher chemical potential to places with lower chemical potential until the chemical potential of both systems are equal. This gives the electronegativity as the negative of the chemical potential: χe=−μ.
Terms and Definitions
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
According to the Lewis definition, an acid is an electron pair acceptor and a base is an electron pair donor. Lewis acids are electrophiles and Lewis bases are nucleophiles. The Lewis definition is used extensively in organic chemistry because a molecule that is an electrophile (electron lover) can have an area of partial positive charge, which will attract an electron. A nucleophile has a partial negative charge, which attracts an electrophile. Lewis acids include substances with no transferable H+ and a Lewis base includes substances with no transferable OH–.
Theoretical investigation of the hydrolysis and DNA binding of platinum (II) complexes of imidazolidine dioximes
Published in Molecular Physics, 2023
Ömer Faruk Emirik, Cansu Şanlı, Vefa Ahsen, Ayşe Gül Gürek, Burcu Dedeoglu
The chemical potential (μ) reflects the ability of an atom in a given molecule to attract electrons and hence to work as an electrophile. Chemical hardness (η) provides information on the stability of a molecule under small perturbations of a chemical reaction. Electrophilicity index (ω) is a measure of electrophilic power of a molecular system towards a nucleophile. Greater the electrophilic power of a molecule, higher is its reactivity as an electrophile. The calculated chemical potential of the complexes is similar to cisplatin; however, the hardness of the cisplatin (and its fully hydrolysed form) is considerably higher than the complexes. The major difference is calculated for the electrophilicity index where the electrophilicity is much lower for cisplatin than the studied compounds. The electrophilicity increases with the fluorine substitutions where the highest electrophilicity is calculated for 2b and the least for 2a. The enhanced electrophilicity of the metal centre in the proposed complexes can be attributed to the incorporation of the imidazolidine dioxime ligand suggesting the potent reactivity of the complexes for the hydrolysis and DNA binding reactions which will be discussed in the next section.
Computation of global reactivity descriptors and first hyper polarisability as a function of torsional angle of donor–acceptor substituted biphenyl ring system
Published in Molecular Physics, 2018
Debkumar Mandal, Rakesh Maity, Hasibul Beg, Guillermo Salgado-Morán, Ajay Misra
The first-order partial derivatives of total energy (E) with respect to the number of electrons (N) at constant external potential, V(r), define chemical potential (µ) and the second partial derivatives of total energy (E) with respect to the number of electrons (N) at constant external potential, V(r), define the global hardness (η) of the system: Calculation of chemical hardness is generally done using a finite difference method as follows: where I.P = ionisation potential and E.A = electron affinity. Using the Koopmans’ theorem in terms of the energies of highest occupied molecular orbital (EHOMO) and lowest unoccupied molecular orbital (ELUMO), Equation (3) and (4) can be expressed as The electrophilicity is a descriptor of reactivity that allows quantitative classification of the global electrophilic nature of a molecule within a relative scale. Parr et al. [35] proposed the electrophilicity index as a measure of energy lowering due to maximal electron flow between donor and acceptor .They defined electrophilicity index as