Journal of Physical Organic Chemistry最新文献

A detailed mechanistic investigation of the Zn (II)-catalyzed Csp–Csp² (Sonogashira-type) cross-coupling reaction is reported herein, using the Density Functional Theory method. The present study unveiled an unconventional non-redox mechanism for Zn-catalyzed cross-coupling reaction, where the oxidation state of Zn remains intact throughout the catalytic cycle. Our study further revealed the significant role of the base in controlling the feasibility of cross-coupling reactions that are catalyzed by electron-deficient metal centers. Our study indicates that K₃PO₄ acts as an ancillary ligand (Lewis base) for the electron-deficient Zn (II) catalytic center rather than as a proton abstractor for the nucleophilic coupling partner (phenylacetylene) in this reaction. The active catalyst was identified to be a four-coordinate bis-DMEDA Zn (II) complex. The mechanism proceeds via the initial activation of the nucleophilic coupling partner (phenylacetylene), followed by the electrophilic coupling partner (organic halide) activation liberating the cross-coupled product by a concerted nucleophilic substitution pathway. The turn-over limiting step was identified to be the activation of the electrophilic coupling partner. The activation barrier obtained for the reaction, 31.0 kcal/mol concords well with experimental temperature requirements (125°C). The coordination by base is found to stabilize the rate-determining intermediates and transition states involved in the reaction. The mechanistic insights gained from this study could aid in the rational design and development of sustainable cross-coupling reactions using zinc as the catalyst.

Amino acid oxidation is fascinating because different oxidants produce diverse compounds. No research has examined how metal catalysts affect amino acid oxidation by diperiodatocuprate (III) (DPC) in micellar environments. This research is crucial to understanding amino acids in redox processes and identifying active species of Ru(III) and DPC. The study will evaluate how cationic surfactant affects Ru(III)-facilitated L-phenylalanine (L-Pheala) oxidation utilizing DPC in an alkaline medium. The reaction's advancement has been assessed employing the pseudo-first-order condition as a gauge for [OH⁻], [DPC], ionic strength, [L-Pheala], [Ru(III)], [IO₄⁻], [Surfactant], and temperature. L-Pheala and DPC interact stoichiometrically in a ratio of 1:4. Across the spectrum of concentrations examined, the reported reaction reflects less than unit order kinematics in relation to both [L-Pheala] (0.61 in the aqueous medium and 0.58 in the CPC micellar medium) and [OH⁻] (0.47 in the aqueous medium and 0.51 in the CPC micellar medium), first-order reliance on the [DPC] and [Ru(III)], and negative fractional-order for [IO₄⁻] (−0.54 in the aqueous medium and −0.56 in the CPC micellar medium). A zero salt effect is suggested by the observed constancy in oxidation rate with the inclusion of electrolytes. The oxidation rate is significantly enhanced by Ru(III) solution (as a catalyst) at ppm concentration. Cetylpyridinium chloride (CPC) micellar media facilitate an additional enhancement (four times) in the rate of the reaction. CPC thus exhibits an excellent compatibility with Ru(III) for the L-Pheala oxidation using (DPC).

The photosensitizer mechanism by the psoralen (PSO) reacts to produce reactive oxygen species has not been thoroughly studied; thus, this work was carried out a study of the reaction and mechanism involved in the photosensitizer activity of PSO, employing M06-2X/6-311++G(d,p) of the density functional theory. There is a competition between the generation of radical anion superoxide (type I mechanism) and the singlet oxygen molecule (type II mechanism) in lipid media; therefore, the ROS anion superoxide and singlet oxygen could be formed as products of the reaction involved in the photosensitizer activity of PSO in lipid media. In aqueous media, the reaction involved in the photosensitizer activity of PSO was only attributed to the type I mechanism; hence, in aqueous media, the photosensitizer activity of PSO yielded the anion superoxide. The present study supports the photosensitizer activity of the PSO in lipid and aqueous media. It enhances the knowledge of these reactions in different media and their application to reactivity, including the physiology media.

Rapid detection of chemical explosives plays a critical role in national security and public safety. An in-depth study of the sensing mechanism is particularly urgent for the development of highly efficient, sensitive, and selective chemical sensors for the precise detection of chemical explosives. Density functional theory (DFT) and time-dependent DFT approaches were used in this work to examine the sensing mechanism of a novel fluorescent probe 1-benzyl-3,5-di (thiophen-2-yl)pyrazin-1-ium bromide (BTPyz) for the detection of 2,4,6-trinitrophenol (TNP). A comprehensive theoretical exploration was carried out, and a different interaction mode between the probe and TNP from that in the original experiment was proposed. The π–π stacking was established to be the recognition interaction between BTPyz and TNP anion, and the active site was determined from the three potential sizes according to the Gibbs free energy analysis results. The rationality of the reaction mode and the π–π stacking product between the BTPyz and TNP (BTN) was further confirmed by the fluorescence properties (absorption and emission spectra). According to the findings of frontier molecular orbitals (FMOs), photoinduced electron transfer (PET) is the intrinsic mechanism through which TNP quenches the probe's fluorescence.

New reaction systems “oxirane – nucleophile X^– – proton-donor reagent AH – solvent” have been proposed for the detection of epoxides in which nucleophilic opening of the oxirane ring occurs accompanied by the formation of a colored product. The kinetic and mechanistic regularities of reactions in the proposed systems were investigated. Reaction orders with respect to the components of the systems have been determined: close to 1 – for oxirane and X⁻, close to 0 – for AH. It was shown that the proposed chromogenic reactions represent nucleophilic substitution of S_N2-type and allow the detection of epoxides containing both a terminal and internal epoxy group, which can be used to monitor processes in systems where epoxides are either the initial compounds or the synthesis products. Based on the conducted studies, it is possible to develop methods for the quantitative determination of epoxides using kinetic methods of analysis and UV–visible spectroscopy.

Herein, a series of fluorinated quinoxaline core–based chromophores (MTH1-MTH6) with A₁–π–A₂–π–A₁ configuration was designed by structural modulation of end-capped acceptors in MTHR. The quantum chemical calculations were accomplished at MPW1PW91/6-311G(d,p) functional to explore optoelectronic and photovoltaic properties of these designed compounds. The findings revealed that all the derivatives exhibited narrow band gap (E_gap = 2.163–2.666 eV) with red shift spectra (610.24–766.944 eV in chloroform) as compared with MTHR. The designed compounds exhibited comparable open-circuit voltage (V_oc) and higher power conversion efficiencies (PCEs) as compared with the MTHR. Among the entitled chromophores, MTH1 was found to be a promising chromophore for organic solar cells (OSCs) owning to its lowest E_gap (2.163 eV) with highest absorption peak (766.944 nm in chloroform and 717.709 nm in gaseous phase). The aforementioned findings indicate that molecular engineering of chromophores with extended acceptors enhances photovoltaic response, and this motivates researchers to develop highly effective photovoltaic devices.

The design and synthesis of insensitive energetic materials are a necessary and challenging work. The synthesis of novel nitrogen-rich salts based on 5-(5-Nitro-1H-1,2,4-triazol-3-yl)-1H-tetrazole (H₂NTT) has been presented. Structural characterization of these two salts was accomplished by utilizing NMR, MS, IR spectroscopy, and X-ray diffraction. The standard heats of formation were calculated, and the differential scanning calorimetry (DSC) and sensitivity test were carried out. Their detonation performances were estimated by EXPLO 5 program. These newly synthesized salts showed highly positive heat of formation and low sensitivity. It is noteworthy that the diaminoguanidine salt b exhibited good detonation performance superior to traditional explosive TNT (Trinitrotoluene), making it a prospective candidate for insensitive energetic material.