Structural and spectroscopic (UV–Vis, IR, Raman, and NMR) characteristics of anisaldehydes that are flavoring food additives: A density functional study in comparison with experiments

Scandium-Catalyzed Phenol-Directed Construction of 5-Carbonyl-4-hydroxybenzofurans via Intramolecular Friedel-Crafts Reaction

Herein we report a scandium-catalyzed regioselective synthesis of 5-carbonyl-4-hydroxybenzofurans via a phenol-directed intramolecular Friedel-Crafts reaction. This synthetic method was applied for the total synthesis of furanoflavones. Experimental studies and density functional theory calculations suggest that hydrogen bond interactions between the phenolic hydroxy group and the scandium complex realize regioselective intramolecular cyclization.

Preparation of double-layered nanosheets containing pH-responsive polymer networks in the interlayers and their conversion into single-layered nanosheets through the cleavage of cross-linking points

Double-layered nanosheets containing pH-cleavable polymer networks between two niobate layers were prepared by copolymerization of N-isopropylacrylamide and an acid-degradable crosslinker via surface-initiated atom transfer radical polymerization on the surface of hydrated interlayers (interlayer I) of K₄Nb₆O₁₇·3H₂O and subsequent exfoliation by the introduction of tetra-n-butylammonium (TBA) ions into anhydrous interlayers (interlayer II). Moreover, the double-layered nanosheets were converted into single-layered nanosheets by the cleavage of cross-linking points in polymer networks by lowering pH. Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG) results showed that polymer networks were present, and nanosheets with a thickness of 10.8 ± 1.6 nm were observed by using an atomic force microscope (AFM) after exfoliation using TBA ions. The thickness of the nanosheets was decreased to 6.1 ± 0.9 nm by lowering the pH, and proton nuclear magnetic resonance (¹H NMR) and UV-vis spectroscopy showed that the degradation of the cross-linkers proceeded, suggesting that the cleavage of the cross-linking points led to the conversion of double-layered nanosheets into single-layered nanosheets.

High-efficiency activation of the C–H bond to synthesize p-methoxy benzaldehyde over a MnO2/CNT/Gr catalyst

The selective oxidation of C(sp3)–H was achieved by the MnO2/CNTs/Gr electrocatalyst: 81.03% faradaic efficiency and 82.73% selectivity of p-methoxy benzaldehyde were obtained.

New Insights on the Vibrational Dynamics of 2-Methoxy-, 4-Methoxy- and 4-Ethoxy-Benzaldehyde from INS Spectra and Periodic DFT Calculations

The dynamics of 2-methoxybenzaldehyde, 4-methoxybenzaldehyde, and 4-ethoxybenzaldehyde in the solid state are assessed through INS spectroscopy combined with periodic DFT calculations. In the absence of experimental data for 4-ethoxybenzaldehyde, a tentative crystal structure, based on its similarity with 4-methoxybenzaldehyde, is considered and evaluated. The excellent agreement between calculated and experimental spectra allows a confident assignment of the vibrational modes. Several spectral features in the INS spectra are unambiguously assigned and torsional potential barriers for the methyl groups are derived from experimental frequencies. The intramolecular nature of the potential energy barrier for methyl rotation about O–CH₃ bonds compares with the one reported for torsion about saturated C–CH₃ bonds. On the other hand, the intermolecular contribution to the potential energy barrier may represent 1/3 of the barrier height in these systems.