Modeling of the Chemico-Physical Process of Protonation of Molecules Entailing Some Quantum Chemical Descriptors

Abstract

Relying upon the basic tenets of scientific modeling, an ansatz for the evaluation of proton affinity of molecules are evolved in terms of a four component model. The components of the model chosen are global descriptors like ionization energies, global softness, electronegativity and electrophilicity index. These akin quantum mechanical descriptors of atoms and molecules are linked with the charge rearrangement and polarization that occur during the physico-chemical process of protonation of molecules. The suggested ansatz is invoked to compute the protonation energy of as many as 43 compounds of diverse physico-chemical nature viz, hydrocarbons, alcohols, carbonyls, carboxylic acids, esters, aliphatic amines and aromatic amines. A detailed comparative study of theoretically evaluated protonation energies of the above mentioned molecules vis-à-vis their corresponding experimental counterparts reveals that there is a close agreement between the theory and experiment. Thus the results strongly suggest that the proposed modeling and the ansatz for computing PA, the proton affinity, of molecules for studying the physico-chemical process of protonation may be valid proposition.

Evaluation of l-tyrosine mixed with sodium dodecyl sulphate or cetyl pyridinium chloride as a corrosion inhibitor for mild steel in 1 M HCl: experimental and theoretical studies

“…57 Table 6 shows that in the mixed form, ionization energy decreases compared to individual system. [64][65][66][67] In the present investigation, the value of DN > 0. Table 6 shows the order of electronegativity (c) as Tyr > Tyr + CPC.…”

Theoretical Study of 3-Amino-1 , 2 , 4-Triazole and Its Protonated Analogue as Corrosion Inhibitors

“…A lower IP indicates less difficulty to remove electrons from a system. [33] Table 1 shows that ATA has a lower IP in the liquid phase than in the gas phase if calculated by the B3LYP method using the energy mode and has a lower IP in the gas phase than in the liquid phase if calculated by same method using the orbital Table 1 that ATA has, according to the orbital parameter method, lower η and higher σ values in the gas phase, which indicates the high reactivity of this molecule in the gas phase. The energy difference between the HOMO and LUMO (ΔE) is a measure of the molecule softness.…”

Predicting collision-induced dissociation spectra: Semi-empirical calculations as a rapid and effective tool in software-aided mass spectral interpretation

“…AM1 performs well in calculating bond lengths, being in good agreement with experimental data (approximately 5% error); however, relative energies of molecules are calculated more accurately by DFT . AM1 tends to overestimate basicity, having been shown to be somewhat less reliable for calculating proton affinities . DFT generates more accurate heats of formation than AM1 …”

“…[19] AM1 tends to overestimate basicity, having been shown to be somewhat less reliable for calculating proton affinities. [20,21] DFT generates more accurate heats of formation than AM1. [22] The authors have used DFT in previous studies with the pharmaceutical compounds fluconazole, maraviroc and dofetilide to rationalise CID product ion spectra in terms of bond weakening resulting from conformational changes.…”