Journal of Physical Organic Chemistry最新文献

In this work, a hierarchical molecular structure method (HMSM) was proposed to extract molecular descriptors. In this method, the molecular structure is divided into three hierarchies: the first hierarchy involves the contributions of the number of vertices (vertex number m and the sum of vertex number effect, S_VNE); the second hierarchy involves the contributions of the vertex skeleton (odd-even index, OEI, and intramolecular polarization effect index, IMPEI); and the third hierarchy involves the contributions of the functional group (polarization effect index, PEI, and group influencing factor, G_N). Using these six molecular descriptors, the normal boiling points (NBP) of aliphatic oxygen-containing organic compounds (AOCOCs), including alcohols, ethers, aldehydes, ketones, carboxylic acids, and esters, can be quantitatively correlated well. The results show that the average absolute percentage error (APPE) between the experimental and calculated NBP values for each series of AOCOCs is less than 1%. Based on the obtained QSPR models, the NBPs of some AOCOCs that have not been experimentally measured were predicted, including 14 alcohols, 25 ethers, 106 aldehydes, 72 ketones, 103 carboxylic acids, and 57 esters. Additionally, a QSPR model for all 518 AOCOCs was also derived, yielding an APPE value of only 1.35%, indicating that the HMSM-based QSPR model performs exceptionally well in the field of QSPR modeling. The specific contributions of functional groups to NBP were discussed and their order is as follows: COOH > OH > COO > C(O) > CHO > O.

Phenyltriaz-1-en-1-yl-4-phenyloxazoles (PTOs) have been identified as photoinduced tautomeric photophysical probes. A series of PTOs has been synthesized and studied for their absorption and fluorescence spectral behavior in different solvent media with varying polarities. PTOs exhibited dual fluorescence behavior and large Stoke's shifts suggesting the presence of tautomeric forms (N* and T*). Dipole moments of PTOs in their excited states were calculated using Bakhshiev, Lippert–Mataga, Reichardt, and Kawski solvatochromic shift methods and were correlated with the theoretical dipole moments for N* and T* forms. The frontier molecular orbitals (HOMO-LUMO) and various physicochemical parameters (χ, η, σ, μ_p, ω, ΔE^II, N_max) were calculated using density functional theory (ground state-(CIS)/B3LYP/6–311++G(d,p)) computations to analyze the excited state intramolecular proton transfer (ESIPT) within these probes. The electrostatic potential (ESP) maps and Mulliken/NBO charges established the electrophilic and nucleophilic sites within molecules and intramolecular proton transfer from one end of the triazeno-bridge to the other end. DFT incorporated dispersion correction (D3(BJ)) accounts for significant van der Waals interactions. In vitro antioxidant activity of PTOs studied using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay revealed them as potential antioxidants. Two multi-parametric scales based on solvent polarity, namely, (i) Catálan and (ii) Abboud-Kamlet-Taft, were employed to analyze the acidity and basicity of PTOs in ground and excited states to provide a plausible mechanism for ESIPT.

[3+2] Cycloaddition reaction of thiazolium ylide with activated acetylene does not yield the expected pyrrolothiazole, in contrast to a similar reaction of other N-cycloiminium ylides. Initially formed [3+2] cycloadduct undergoes thiazole ring opening followed by a thiol-yne type nucleophilic addition on second molecule of activated alkyne to give E,Z and/or Z,Z isomers of 1:2 adduct. We have investigated the reaction of thiazolium ylides with alkyl propiolate computationally at DFT level to understand the impact of stereochemical control on mechanistic aspects. Relatively more stable conformer of thiazolium ylide leads to a thermodynamically as well as kinetically preferred diastereomer of the cycloadduct having trans orientation of hydrogen atoms, which restricts the auto-oxidation and facilitates the ring opening. Formation of the Z or E isomer in subsequent thiol-yne reaction depends on the stereochemical control of the allene or allenoate intermediate. Experimentally observed reactivity of thiazolium ylide is computationally rationalized on the basis of the CDFT-based reactivity indices and the stereochemical control on reaction mechanism.

The current study was aimed at synthesizing (E)-2-(((3-hydroxy-4-methylphenyl)imino)methyl)-4,6-diiodophenol (1) and (E)-3-((2-hydroxy-3,5-diiodobenzylidene)amino)-4-methylbenzoate (2). The modern spectral tools like UV–Vis, FTIR, and NMR were used to determine the structures, while a single X-ray diffraction approach was employed to prove that Compound 2 is orthorhombic and Compound 1 is triclinic. The 6-31G(d,p) basis set along B3LYP (hybrid functional) was used for the optimisation of synthesized compounds. The energy gaps between various orbitals were estimated using DFT calculations, and a comparative study in terms of different structural parameters was also conducted, which confirmed the correlation between XRD and DFT measurements. Two-dimensional fingerprint plots and Hirshfeld surface analysis were used to further elucidate the different interactions that stabilize the crystal. In vitro and in silico studies were employed to assess the biological potential of these molecules in terms of enzyme inhibition. Compound 2 depicted 74.17 ± 1.4% and 69.11 ± 1.3% inhibition against AChE and BChE, respectively. The docking score, as well as in vitro studies, demonstrated that Compound 2 is more potent than Compound 1 against acetylcholine esterase and butyrylcholine esterase.

The quantum chemical study of the oxidation reaction of the 1,4-dihydropyridine and series of dihydroazolopyridines has been undertaken. The one-electron transfer processes as a key reaction stages and corresponding ionization potentials (I_HetH2 and I_HetH•) have been discussed. The azole ring effect on the electronic structure of the partially hydrogenated ring in the initial molecules and radicals as well as ionization potentials have been analyzed. The difference in the pyridine-like and pyrrole-like nitrogen atoms effect on the oxidation process has been observed.

The Curtin–Hammett principle, widely recognized in thermal reactions, has been extended to photosensitization processes in this study, providing new insights into the reactivity of photogenerated singlet oxygen (¹O₂) with phenol and phenolate anion species. Here, we explore mechanistic and Curtin–Hammett studies of the equilibrium between the phenol and phenolate anion forms of a prenylated natural product, prenylphloroglucinol. This study uses density functional theory (DFT) to examine phenol and phenolate anion-quenching pathways of ¹O₂ showing distinct pathways for each form. In the phenolate anion, ¹O₂ is quenched to form a peroxy anion. In contrast, in the phenol form, ¹O₂ leads to a potent epoxidizing agent in a seemingly pro-oxidant path. An iso-hydroperoxyhydrofuran intermediate is proposed to be key in the epoxidation. Meanwhile, the phenolate anion cyclizes and protonates forming a comparatively benign hydroperoxyhydrofuran species. The phloroglucinol is next to the C-prenyated group directs the reaction pathway towards the formation of a dihydrobenzofuran, deviating from the conventional ¹O₂ “ene” reaction mechanism and the production of allylic hydroperoxides typically observed in trisubstituted alkenes.

Nonclassical hydrogen bond (NCHB) as a weak interaction force not only plays an important role in organic conversion and catalysis but also has significant implications for understanding and predicting the properties of compounds. At present, the influence of homoring competition effect of substituents on the intramolecular properties of NCHB has not been studied. In this work, 51 diphenylnitroketone XArCH=N(O)ArY (XPNY) compounds containing different substituents were chosen as model molecules, the bond energy (E_HB) in CH⋯O and aromaticity of quasi-aromatic ring (PDI_Q) were computed, and the chemical shifts δ_H(CH⋯O) of ¹H NMR in CH⋯O were collected or measured. This work focuses on analyzing the NCHB CH⋯O hydrogen bond in compounds XPNY and explored the influence of homoring competition effect of substituents on the energy E_HB of CH⋯O and chemical shift value δ_H(CH⋯O). The results show that (1) the chemical shift values δ_H(CH⋯O) of CH⋯O in XPNY are abnormally large, and the values of E_HB are 14.15–15.51 kJ/mol, lower than 16.74 kJ/mol, which is consistent with the characteristics of intramolecular NCHB. Therefore, it can be considered that the CH⋯O hydrogen bonds are NCHB in XPNY. (2) The substituent X in compound XPNY exhibits the homoring competition effect. (3) The aromaticity of quasi-aromatic ring Q is the main factor affecting the E_HB. The substituent X affects the E_HB and δ_H(CH⋯O) along different paths. This study can help understanding the impact of substituent effects on NCHB in depth.

Although the energies of intermolecular hydrogen bonds, E_HB, can be ascertained by a variety of approaches, there is not a general method to accurately determine the energies for intramolecular hydrogen bonds, E_IMHB. Structures for compounds X(CH₂)_nOH {X = F, OH, NH₂, Cl, Br, SH; n = 4–5} are calculated and then “clipped” to form complexes CH₃CH₂X•CH₃CH₂OH such that the critical geometric, spectroscopic, and electron density features are preserved. The E_IMHB of the parent molecule is assumed to equal the E_HB of the complex. Of the previous methods of determining E_IMHB, the molecular tailoring approach (MTA) comes closest to the values from this work with the differences due to incomplete cancellation of conformational effects in the MTA. In general, parametric methods fare poorly, only being effective for groups of similar molecules. The cis–trans and isodesmic approaches are of limited value for longer carbon chains due to conformational strain.