Journal of Physical Organic Chemistry最新文献

The reuse of waste and the use of renewable materials are of great environmental and economic interest. With that in mind, the synthesis of mesoporous silica can be performed using rice husk ash, which is an industrial waste generated in large quantities. This mesoporous material can be functionalized with photoactive molecules, enabling application in photocatalysis. In this work, we used mesoporous silica nanoparticles functionalized with rose bengal dye (RB) for photooxidation reactions of organic molecules, such as the antibiotic cefuroxime 1-acetoxyethyl ester (cefuroxime axetil). The characterization results showed the formation of one-dimensional channels with uniform size and two-dimensional hexagonal arrangement, with surface area and pore diameter of 230 m² g⁻¹ and 5 nm, respectively. The infrared and UV-Vis spectroscopy indicated the functionalization of silica with photoactive molecules. Finally, SBA-15/RB was applied for the photooxidation of ascorbic acid and antibiotic cefuroxime axetil under irradiation with green light, proving to be efficient for the degradation of cefuroxime axetil. Investigation of the reactive oxygen species involved in photodegradation showed that the photooxidation mechanism mainly involves singlet oxygen.

Rate and product data are reported for the solvolysis reactions of 27 mono, di [3,4] and tri [3,4,5] ring-substituted benzyl chlorides. The first order rate constant for solvolysis in 20% acetonitrile in water decrease from k_solv = 2.2 s⁻¹ for 4-methoxybenzyl chloride to 1.1 × 10⁻⁸ s⁻¹ for 3,4-dinitrobenzyl chloride. The product rate constant ratios k_MeOH/k_TFE for solvolysis in 70/27/3 (v/v/v) HOH/TFE/MeOH range from a minimum of k_MeOH/k_TFE = 8 to a maximum of 110. The rate data were fit to a four-parameter Hammett equation that separates the resonance ($�{\rho }_r�{\sigma }_r$) and polar ($�{\rho }_n�{\sigma }_n$) effects of the aromatic ring substituents on the reaction rate. Increases in the values of the Hammett reaction constants $�{\rho }_r$ and $�{\rho }_n$ are observed as the substituent constants $�{\sigma }_r$ or $�{\sigma }_n$ are increased. A sharp decrease in the product selectivity k_MeOH/k_TFE = 26 for stepwise solvolysis of 4-methoxybenzyl chloride is observed as electron-withdrawing meta-substituents are added to 4-methoxybenzyl ring due to a Hammond-effect on the position of the transition state for solvent addition to the substituted 4-methoxybenzyl carbocation reaction intermediates. Sharp increases in the selectivity k_MeOH/k_TFE are observed with decreasing reactivity of other 3,4,5-subsituted benzyl chlorides due to anti-Hammond shifts, on a two-dimensional More–O'Ferrall reaction coordinate diagram, in the position of the transition state for a concerted solvolysis reaction.

An efficient and green synthesis of tetramethyl-10-(phenylamino)-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione derivatives has been achieved from various substituted aryl aldehydes, 5,5-dimethyl-3-(2-phenylhydrazinyl)cyclohex-2-enone and dimedone in aqueous ethanol medium. Environment-friendly reaction, excellent yields, operational simplicity and shorter reaction times are the significant features of the present protocol. All the synthesized compounds were characterized by various spectroscopic techniques and X-ray crystal diffraction studies.

In organic chemistry textbooks, the electron resonance states are used to explain the orienting effect of benzene substituent. However, these resonance states do not exist in the C₆H₅-S + E⁺ electrophilic addition, so the resonance state discussions actually are meaningless. The density functional theory (DFT) calculation shows that the C₆H₅-S + E⁺ addition follows the transition state theory and needs to overcome a barrier. Benzene molecule C₆H₆ has two degenerate highest occupied molecular orbitals (HOMOs), but after becoming substituted benzenes, the two HOMOs split to HOMO and HOMO-1 with different orbital energies and electron distributions. It makes the addition barrier on two or three benzene ring carbons is low, and the addition rate is fast, but the barrier of other carbons is high, and the rate is slow. Therefore, substituent splits the two degenerate HOMOs of benzene molecule, which is the origin of substituent orienting effect. For the substituted benzenes with halogen group -X and electron-releasing group, their HOMO images alone can determine that the two types of substituents are the ortho- and para-orienting groups, but for the substituted benzenes with electron-withdrawing group, their HOMO alone cannot determine whether the substituent is a meta-orienting group. The study found that atomic polar tensor (APT) charges are a good judgment index of substituent orienting effect because based on its physic-chemical model, the charges represent the number of active electrons on the benzene ring carbons. The DFT calculation gives the APT charges of 19 mono-substituted and 12 di-substituted benzenes and some aromatic molecules. The APT charges can all correctly determine their orienting effects, showing that APT atomic charge from quantum theoretical calculation is a good substituent orienting index.

Zinc 13-(N,N-diethylamino)methyl-3,3,7,8,12,17,18-heptaethyl-2-oxochlorin was prepared from 2,3,7,8,12,13,17,18-octaethylporphyrin via the regioselectively acid-catalyzed double dehydration of cis-12,13-diethyl-cis-12,13-dihydroxy-2-oxobacteriochlorin to the corresponding 12-ethyl-13-vinyl-2-oxochlorin. The synthetic zinc amino-oxochlorin was axially ligated with the imidazolyl group of N^α-protected histidines in chloroform, and concomitantly the amino group of the former was hydrogen-bonded with the carboxy group of the latter. The resulting two-point bonding supramolecules served as models for the complexes of chlorophylls with peptides in photosynthetic apparatuses including light-harvesting antennas and charge-separating reaction centers. A similar 1:1 complex was produced by the interaction of the zinc amino-chlorin with the related methionine possessing thioether and carboxylic acid moieties.

Earlier experimental works report the synthesis of zwitterions with anionic p-dicyanomethanide (coupled to benzene and thiophene) donors. In this report, four such zwitterions (two metameric pairs) are investigated using HF, B3LYP, CAM-B3LYP, HSE06, and ωB97xD methodologies. This work is focused on (1) metameric (Reichardt's and Brooker's) induced conformational selectivity (twisted vs. planar) and (2) efficiency assessments of benzene- versus thiophene-based anionic donors. These effects were found to have significant influences on many tensorial and nontensorial properties. For Reichardt's type, large twisting was observed for the benzene case and lower twisting for the thiophene case. Enhanced first hyperpolarizability were observed for Reichardt's type (257.2 × 10⁻³⁰ esu) than Brooker's type (67.2 × 10⁻³⁰ esu), thus indicating the former type to be more efficient (approximately fourfold enhancement) chromophore (approximately seven-time enhancement for thiophene-based systems). Similarly, between the benzene versus thiophene cases, enhanced hyperpolarizabilities were observed for the former (257.2 × 10⁻³⁰ esu) than the latter type (112.0 × 10⁻³⁰ esu), indicating the benzene type as more efficient (more than twofold enhancement) donor (approximately four-time enhancement for Brooker's types). The structure–property manipulations strategies investigated here can be used as valuable tools in the designing of efficient functional molecular materials for various fundamental applications.

Waqas Amber Gill¹ | Muhammad Usman Khan² | Zunaira Shafiq³ | Muhammad Ramzan Saeed Ashraf Janjua³

Gill, W. A., Khan, M. U., Shafiq, Z., Janjua, M. R. S. A., “Exploring the Intermolecular Interactions in Carbon Disulfide Dimer: An Ab Initio Study Using an Improved Lennard-Jones Potential Energy Surface for Physical Insights,” J Phys Org Chem 2023, https://doi.org/10.1002/poc.4548. The above article, published online on 05 June 2023 on Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal's Editor in Chief, Professor Rik Tykwinski, and John Wiley and Sons LLC. The journal's Editor-in-Chief was contacted by a third party who raised concerns about the article. An independent scientific expert evaluated the article and confirmed that significant problems exist with the data and conclusions of the work, and that it contains inadequate and/or inaccurate citations. As a result, the editors consider the article's conclusions to be unreliable.

Photochromic azobenzenes undergo light-mediated trans–cis isomerization. The cis isomer reverts to the trans isomer thermally. To investigate the effect of different monomer sequences on the thermal stability of cis-azobenzene, a series of copolymers, namely, block, and random structures containing stearic acid and azobenzene moieties as their side chains have been synthesized through reversible addition–fragmentation chain transfer (RAFT) polymerization. In this study, we investigate the photoisomerization of the trans and cis forms of the polymers and also the thermal reversal of the cis-azobenzene photochromic systems. The isomerization data revealed significant differences in the isomerization timescales between the polymers and the corresponding monomer. It was observed that the local polarity around the azobenzene units within a polymer was significantly influenced by the chain segment depending on whether it was in the vicinity of the hydrophobic alkyl chains or other azobenzene units. This local environment of the azobenzene units regulates the stabilization of the transition states during the cis–trans thermal isomerization, consequently affecting the half-life of the cis isomer.