Physical Properties of Phenol Compound: Semi-empirical Calculation of Substituent Effects [Part One]

Abstract

Problem statement: Physical properties of phenol compound such as steric energy, charge of oxygen, ionization potential, dipole moment, LUMO and bond length have been calculated. Approach: All molecular geometries were minimized by quantum mechanic especially at (AM1) method was used to investigate the effect of a variety of substituents on the phenol (. Global descriptor such as electronic chemical potential (µ), hardness (η), the maximum electronic charge and global electrophilicity index (ω) were determined and used to predict the (pKa) values. Results: The theoretical results (predictive values) found were in good agreement with experimental values. The predictive pKa calculated values by AM1 method gave excellent results with experimental values. The correlation between the predicted values especially global electrophilicity index showed excellent qualitative agreement with the experimental pKa (R2 = 0.95). Conclusion: The present research was to calculate the physical properties of phenol derivatives. Then, the calculated values were compared, quite favorably with experimental values of these properties. In future, we can predict any substituent of set of a phenol compound and compare its value with the experimental.

Update 2 of: Electrophilicity Index

“…As is demonstrated in the case of highly hindered polyanionic chelating ligands, sometimes the theoretical values even suggest 263,264 possible efficient synthetic protocols. Electrophilicity index and its variants have been found to be useful in understanding spectral shifts in acetone, 290 excited-state properties of organic dyes, 291 R-pinene isomerization reaction, 292 application of 8-hydroxyquinoline metal complexes in organic light-emitting diodes, 293,294 internal rotation barrier in alkanes, 295 acceptor properties of quinonederivatized polypyridinic ligands, 296 reactivity of exohedral fullerenes C 64 X 4 , 297 cyclopolymerization reactions of diallyl monomers, 298 properties of pyridine-derived N-heterocyclic carbenes, 299 hydrolytic deamination of a cytosine derivative in a protic medium, 300 reactivity of pyridine derived Nheterocyclic germylenes, 301 radical stability in terms of bond dissociation enthalpies, 302 chemical reactivity of pyrrole derivatives, 303 chemical explosivity, 304 thermal stability of nitroaromatic compounds, 305 properties of phenol compounds, 306 nucleophilic behavior of benzofused thieno [3,2b] furans, 307 hydride affinity of quinines, 308 stability of N-heterocyclic silylenes, 309 reactivity of coinage metal clusters, 310 modulation of N 2 activation in triamidoamine-Mo complexes, 311 reactivity of nickel-modified platinum cluster, 312 active site in bis(imino) pyridyl iron catalyst, 313 etc. Several other popular electronic concepts like electronegativity, 314 charge transfer descriptor, 315 electron-acceptor characteristics, 316 reactivity of paracyclophanes, 317 etc.…”

Effects of Substituents on the SN2 Free Energy of Activation for α-O-4 Lignin Model Compounds

“…What is most striking about these results is the clear presence of nonadditive interactions between these substituents. The magnitude of the effects of individual substituents on reactivity can be expressed in the dimensionless Hammett σ para and σ meta parameters, − which predict that a para hydroxyl group should donate electron density to the ring with a strength of −0.37 (the negative sign indicates donation) while a methoxy substituent at the meta position should withdraw electron density with a strength of +0.12. For the case of this mechanism, a simplistic view of the substituent effects could be that the donation of electron density to a position near the α-carbon should lower the barrier because of the increased stabilization of the S N 2 transition-state structure that involves a “hypervalent”, and hence more positively charged, carbon.…”

General Analytical Procedure for Determination of Acidity Parameters of Weak Acids and Bases

“…The acidity of the phenol group (OH-acid) depends on the substituent of the aromatic ring and its p K a ranges from 4 to 11 [ 8 ]. We have performed the titration and relevant calculations for several mixtures of phenolic compounds, exemplified by 4-NO 2 phenol and a drug N-(4-hydroxyphenyl)acetamide (paracetamol) with different type of organic acids and bases as titrands D. The results are summarised in Table 8 .…”

“…Recently, some theoretical approaches were employed to predict the p K a value, for example, ab initio quantum mechanical calculations [ 3 , 4 ] or QSPR (quantitative structure-property relationship) modeling [ 5 , 6 ] as well as QSPR models which employ partial atomic charges as descriptors [ 7 , 8 ]. The theoretical models take into account electronic effects (induction, resonance), solvation of compounds of type HA, BH and their ionic forms, that is, A − and BH + , hydrogen bonding, and various stereochemical effects.…”