جستجوی مقالات مرتبط با کلیدواژه « microwave » در نشریات گروه « شیمی »

Efficient synthesis of naphthopyranopyrimidine derivatives using copper(II)/polyimide linked covalent organic frameworks (Cu(II)/PL-COF) has been achieved through a solvent-free and microwave-assisted method. This one-pot protocol combines β-naphthol, aromatic aldehydes, and N,N-dimethylbarbituric acid. The process offers various advantages, including safe operation, minimal pollution, fast product formation, and easy setup due to microwave irradiation and a lack of solvents. Additionally, the catalyst demonstrates high reusability, allowing for multiple repetitions of the reaction without experiencing any significant loss in activity.

In this work, N-vinyl imidazole (NVI) and glycidyl methacrylate (GMA) were combined to create Poly(NVI-GMA). The synthesis of this novel cationic copolymer was initiated using high-temperature, ultraviolet (UV), and microwave radiation. The cationic level of Poly(NVI-GMA) was optimized during the copolymerization process. The ideal synthesis conditions included a 2% initiator concentration, equal proportions of NVI and GMA (50% (v/v) each), a polymerization duration of 4 minutes, and an acidic pH reaction media. UV-visible, FTIR, and 1H-NMR techniques were employed to examine the structure of the copolymer. To investigate the flocculation performance of the highly cationic Poly(NVI-GMA) in purifying water with high turbidity, several analyses, including Fourier transform infrared (FTIR), X-ray diffraction (XRD), and thermogravimetric (TGA) analyses, were conducted to study and summarize the flocculation mechanism. Experimental simulations utilizing maghnite as a coagulant yielded a transmittance of 96.9% in the supernatant with a concentration of 6 mg/L, a brief stirring duration of 20 minutes, an acidic pH, and a stirring speed of 200 rpm

Extensive research has begun on the production of naturally occurring red colorants as permitted food additives. The Betalain in Beetroot (Beta vulgaris) cells can be used to prepare a natural red color additive for food products. Betalains are more resistant to acidic conditions and high temperatures than other red pigments such as anthocyanins. However, the low stability of Betalain compared to synthetic colorants is considered a big challenge in its extraction, processing, and storage. Therefore, it is very important to use a suitable extraction method for it. In recent years, the use of supercritical carbon dioxide (scCO2) for isolation and extraction of natural products instead of conventional methods such as extraction with organic solvents has attracted interest because the final product may become contaminated with the solvents. In the same vein, this research evaluated the effects of microwave power (100-450 W), carbon dioxide flow rate (1-3 mL/min), temperature (30-70℃), and pressure (15-40 MPa) on extraction efficiency, 2,2-diphenyl-1-picrylhydrazyl, and the quantities of phenolic compounds extracted from Beetroot. The results suggested that temperature, pressure, flow rate, and microwave power significantly influenced the amounts of phenolic compounds, extraction efficiency, and antioxidant properties of the compounds extracted from Beetroot. Increases in temperature, pressure, microwave power, and carbon dioxide flow rate in the (50-60℃), (20-30 MPa), (300-400 W), and (1-2 mL/min) ranges, respectively, increased the quantities of phenolic compounds, ability to suppress free radicals and extraction efficiency as the response. However, increases beyond the mentioned ranges caused decreases in the response variables. Optimal extraction of Betalain from Beetroot using supercritical carbon dioxide and microwave pretreatment was achieved at a temperature of 45 °C, pressure of 27.5 MPa, CO2 flow rate of 2 mL/min, and microwave power of 300W.

Microwave energy is non-ionizing radiation that causes the molecule to move and is a good way to extract compounds from plant extracts. This study aimed to investigate the effect of three independent variables including solvent type (water and methanol 80%), time (3, 6, and 9 minutes), and microwave power (100, 200, and 300 watts) on the flavonoids, anthocyanins, antioxidant properties (IC50) of the Persian Golnar plant or Punica granatum var. pleniflora (PGP) extract. According to results, simultaneous optimization of extraction conditions with 95.609% desirability in 300-watt microwave power, 9 minutes, and use of methanol solvent the flavonoid content was 5.7597 mg /g, anthocyanin content was 4.7983 µmol/g, and IC50 value was 6.5063 mg/ml. The highest average of minimum inhibitory concentration and minimum Bactericidal concentration of PGP extract were 1250 and 5000 µg/ml, respectively against Clostridium perfringens and Escherichia coli, and the better antimicrobial effect was against Staphylococcus aureus with the highest diameter of zone of inhibition (11 mm) compared to Escherichia and Clostridium perfringens. According to the results of this study, microwave pretreatment with optimized conditions can be used to extract significant amounts of phenolic and antimicrobial compounds of PGP extract as a rich source of antioxidants with minimal damage to its effective compounds.

Bis (1(3-trimethoxysilylpropyl)-3-methyl-imidazolium) copper tetrachloride tethered to colloidal silica nanoparticles have been used as an efficient catalyst for the preparation of 2,4-diamino-6-arylpyrimidine-5-carbonitrile derivatives by the one-pot reaction of aromatic aldehydes, malononitrile, and guanidinehydrochlorideunder conventional heating, microwave and ultrasound irradiations. The catalyst was characterized by 1H NMR spectroscopy,dynamic light scattering (DLS), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and thermogravimetric analysis (TGA). The remarkable advantages of this methodology are easy work-up, short reaction times, high to excellent product yields, operational simplicity, low catalyst loading and use of ultrasonic irradiation as a valuable and powerful technology.