Journal of Physical Organic Chemistry最新文献

SmI₂ is a versatile reagent in single electron transfer-mediated reductive transformations. Photoexcitation of SmI₂ generates a reactive excited state capable of transferring an electron to substrates that are recalcitrant towards accepting electrons. Synthetic results unequivocally indicate light as a green and sustainable promoter of SmI₂-mediated chemistry, with the potential to replace the suspected carcinogen hexamethylphosphoramide (HMPA). Rate constants of photoinduced electron transfer from SmI₂ are in the range of 10⁷–10⁹ M⁻¹ s⁻¹, which are an order of magnitude higher in comparison with the ground state process. Recent advancement in Eu^II- and Ce^III-based photo-redox catalysis rejuvenated the area of photo-catalyzed reactions of low-valent lanthanides. This review article aims to illustrate the role of photoexcitation on SmI₂-mediated reductive transformations.

A variety of novel naphthimindazol-N-oxides and naphththiazol-N-oxide have been prepared in a simple two-step process. The first step involves the reaction of 1-chloro-2,4-dinitronaphthalene with glycine, alanine, glycolic acid, thioglycolic acid, and their methyl esters affording substitution products, the subsequent treatment of which with base furnishes naphthimindazol-N-oxide and naphththiazol-N-oxide derivatives. Stepwise reaction mechanisms via carbanions, nitrogen anions, and spiro Meisenheimer intermediates are proposed. The action of 10% NaOH in dioxane on the substitution products was measured spectrophotochemically, and the kinetic studies suggested that the N-naphthyl glycine and N-naphthyl alanine follow a second-order rate law while S-naphthyl thioglycolic acid is accurately first-order kinetics.

Excited-state intramolecular proton transfer (ESIPT) reaction, as one of the most fundamental photochemical behaviors, plays a crucial role in the design of novel optical materials. This study investigates the photo-induced hydrogen bonding behaviors and related ESIPT process of 3-(1H-phenanthro[9,10-d]imidazol-2-yl)-9-phenyl-9H-carbazol-4-ol (CHPHI) in solvents with varying polarities. Based on analyses of the core-valence bifurcation (CVB) index, geometrical structure parameters, topological analysis, and infrared (IR) vibrational spectra, we infer that light excitation facilitates the enhancement of intramolecular hydrogen bonding. This phenomenon can promote the ESIPT process. In particular, we have observed that the enhancement of hydrogen bonding becomes more pronounced as solvent polarity weakens. To further investigate the relationship between solvent polarity and ESIPT behavior, we conduct an exploration of the frontier molecular orbitals (MOs) in CHPHI. Finally, by comparing the magnitudes of excited-state barriers in different solvents, we claim that nonpolar solvents drive the ESIPT reaction for CHPHI fluorophore.

In the current paper, the adiabatic ionization potentials (AIP) for 29 hydantoin derivatives and hydantoin-based drugs such as allantoin, phenytoin, mephenytoin, nilutamide, iprodione, nitrofurantoin, and ethotoin were calculated using the double hybrid ωB97XD density functional theory (DFT) in coupling with 6-311+G(2df,2p) basis set at the B3LYP/6-31+G(d,p) optimized geometry. The neutral and cationic radicals of the examined species were firstly optimized using the B3LYP/6-31+G(d,p) level. Final energies were improved by single point calculation using 16 different DFT methods such as B3LYP, ωB97, B97D, TPSSTPSS, M06-2X, …, and so forth, with 6-311+G(2df,2p) basis. Statistical tools such as root mean square error (RMSE) was used to examine the accuracy of the DFT method with respect to the standard reference AIP values. These standard references were calculated, for 12 hydantoin derivatives with less than nine non-hydrogen atoms, by taking the average values of the AIP computed using the G4, G3B3, and CBS-QBS methods. The vertical ionization potentials (VIPs), the vertical electron affinity (VEA), and global quantum parameters such as electrophilicity and nucleophilicity of the 29 molecules were also calculated. Substitution effect on the AIP, VIP, VEA, fundamental gap, electrophilicity, and nucleophilicity of the species under probe was studied and discussed. The results reveal that substitution of electron withdrawing group (EWG) raises the AIP and VIP, electrophilicity, and the fundamental gap, while substitution of electron donating group (EDG) raises the VEA and the nucleophilicity. Furthermore, the condensed Fukui functions were used to identify the active centers for nucleophilic, electrophilic, and free radical attacks.

A select history of dichlorocarbene chemistry between 1950 and 2010 will be presented. This is not a comprehensive review; rather, it is a personal perspective on the contributions of two respected colleagues, the reactive intermediate that spanned their research efforts, and their important contributions to organic synthesis and mechanistic thinking.

As an organic molecule catalyst, N,N′,N″-trihydroxyisocyanuric acid can selectively catalyze the oxidation of the methyl group of waste 2,4,6-trinitrotoluene to generate 2,4,6-trinitrobenzoic acid. This reaction can avoid environmental pollution by inorganic heavy metal catalysts. In this study, four reaction stages of this catalytic reaction were designed and validated computationally at the M06-2X-D3ZERO/6-311G(d,p) level using the acetic acid solvent model. These validations include transition state searches, intrinsic reaction coordinate calculations, reactant and product optimizations, and frequency calculations. The final reaction network of 23 transition states shows that after N,N′,N″-trihydroxyisocyanuric acid activation and common reaction, the network bifurcates into two stages: alcohol to carboxylic acid and aldehyde to carboxylic acid. Although the former stage releases about 155 kcal/mol of Gibbs free energy, less than the 177 kcal/mol from the latter stage, the overall reaction equation shows that the pathway including former stage does not consume the catalytically active substance IM_T2, which saves the energy required for reactivation and is thus more favorable. Furthermore, the key transition states in the reaction network include bimolecular substitution reactions and proton-hopping transfer reactions. Analyses of their interaction region indicators and intrinsic reaction coordinate results demonstrate strong selectivity. Additionally, the energy barriers and heat releases of the latter are twice and 1.3 times greater than those of the former, respectively. In summary, this study elucidated two competitive reaction pathways and identified the more energetically favorable and selective pathway, and it provides useful insights for further optimization of industrial utilization of 2,4,6-trinitrotoluene.

The Diels–Alder cycloaddition of cyclopentadiene and nitroethene, the intramolecular cycloaddition between a diene and triene, and the Diels–Alder cycloaddition of 2-hydroxyacrolein with 1,3-butadiene involving post-transition-state bifurcation (PTSB) were studied. These cycloaddition reactions were investigated using quasi-classical trajectory (QCT), classical molecular dynamics (MD), ring-polymer molecular dynamics (RPMD) simulations, and supervised machine-learning binary classification techniques. Room-temperature dynamics simulations started from the ambimodal transition state (TS) using the QCT, classical MD, and RPMD methods presented similar dynamics. Binary classification revealed that the initial geometry displacement from the ambimodal TS for the Diels–Alder cycloaddition of cyclopentadiene and nitroethene contributed to the branching dynamics and that the initial momenta for the intramolecular cycloaddition between a diene and triene and the Diels–Alder cycloaddition of 2-hydroxyacrolein with 1,3-butadiene played a significant role in the bifurcation dynamics.

The mixed valence (MV) radical anions of several bis(dioxaborines) with aromatic bridges of different length were studied by Vis/NIR spectroscopy, cyclic voltammetry, and theoretical calculations. The phenyl-bridged (1), the biphenyl-bridged (2), and bithiophene-bridged (5) radical anions show intense low-energy intervalence bands with vibrational structure typical of charge delocalized mixed valence species in the range of solvents studied. However, by subtracting from the experimental spectra of 2⁻ in MeCN the fraction corresponding to the delocalized part (taken as the spectrum in tetrahydrofuran [THF]), we get a localized charge-transfer bands that show a significant cutoff effect at the low-energy side, as predicted by classical Marcus–Hush theory. In the radical anions with three aromatic rings on the bridge, the localization of the charge changes with solvent. These radicals are predominantly charge-localized in the high λ_S solvent MeCN, charge-delocalized in the low λ_S solvent THF, and show both type of intervalence bands in DMF. Experimental results and theoretical calculations show that the electronic coupling between dioxaborine units in these three-ring bridged radical anions increases with the number of thiophene rings on the bridge.