scholarly journals Microwave Heating of Liquid Crystals and Ethanol-Hexane Mixed Solution and Its Features (Review)

2021 ◽  
Author(s):  
Akira Naito ◽  
Yugo Tasei ◽  
Batsaikhan Mijiddorj ◽  
Izuru Kawamura ◽  
Kazuyoshi Ueda
Keyword(s):  
Liquid Crystals ◽  
Chemical Shift ◽  
Microwave Irradiation ◽  
Microwave Heating ◽  
Chemical Reaction ◽  
Md Simulation ◽  
Bulk Temperature ◽  
Mixed Solution ◽  
Microwave Effect ◽  
Low Entropy

Microwave heating is widely used to accelerate organic reactions in the chemistry field. However, the effect of microwaves on chemical reaction has not yet been well characterized at the molecular level. In this review chapter, microwave heating processes of liquid crystals and an ethanol-hexane mixed solution under microwave irradiation were experimentally and theoretically investigated using in situ microwave irradiation nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulation, respectively. The temperature of the solution under microwave irradiation was estimated from a chemical shift calibrated temperature (CSC-temperature) which was determined from the temperature dependence of the 1H chemical shift. The CSC-temperatures of CH2 and CH3 non-polar protons of ethanol reflect the bulk temperature of a solution by the thermal microwave effect. The lower CSC-temperature of the OH polar protons in ethanol and much higher CSC-temperature of H-C=N (7′) and CH3-O (α’) protons of N-(4-methoxybenzyliden)-4-butylaniline with respect to the bulk temperature are attributed to the non-thermal microwave effects. According to the MD simulation under microwave irradiation, the number of hydrogen bonds increased in the ethanol-hexane mixed solution as a result of a non-thermal microwave effect. It is concluded that a coherently ordered low entropy state of polar molecules is induced by a non-thermal microwave effect. The ordered state induces molecular interaction, which may accelerate the chemical reaction rate between molecules with polar groups.

scholarly journals TMSOTf-catalyzed synthesis of trisubstituted imidazoles using hexamethyldisilazane as a nitrogen source under neat and microwave irradiation conditions

RSC Advances ◽  
2021 ◽  
Vol 11 (45) ◽  
pp. 28061-28071
Author(s):  
Kesatebrhan Haile Asressu ◽  
Chieh-Kai Chan ◽  
Cheng-Chung Wang
Keyword(s):  
Microwave Irradiation ◽  
Nitrogen Source ◽  
Microwave Heating ◽  
Solvent Free ◽  
Solvent Free Conditions

Trisubstituted imidazoles are synthesized efficiently from the readily available 1,2-diketones and aldehydes using hexamethyldisilazane as a new and stable nitrogen source under TMSOTf-catalysis system, microwave heating and solvent-free conditions.

Discotic liquid crystals of transition metal complexes, 54: Rapid microwave-assisted synthesis and homeotropic alignment of phthalocyanine-based liquid crystals

2017 ◽  
Vol 21 (07n08) ◽  
pp. 476-492 ◽  
Author(s):  
Toshiyuki Akabane ◽  
Kazuchika Ohta ◽  
Tokihiro Takizawa ◽  
Takehiro Matsuse ◽  
Mutsumi Kimura
Keyword(s):  
Liquid Crystals ◽  
Reaction Time ◽  
Microwave Heating ◽  
Phase Transfer ◽  
Difficult Problem ◽  
Phase Transfer Catalyst ◽  
Microwave Assisted Synthesis ◽  
Aliquat 336 ◽  
Large Area ◽  
Homeotropic Alignment

The most difficult problem on syntheses of the phthalocyanine-based liquid crystals is the long reaction time. In order to shorten the reaction time, we have developed novel Methods A, B and D, for the syntheses of phthalocyanine-based liquid crystals by using microwave heating and/or adding a phase transfer catalysis of Aliquat 336. A series of phthalocyanine derivatives C[Formula: see text]PcZn(1) ([Formula: see text] 10, 12, 14, 16 and 18: a, b, c and e) could be successfully synthesized in a dramatically short reaction time of 30–60 min using Methods A and B by microwave heating. On the other hand, anothor series of the derivatives C[Formula: see text](OH)PcZn (2a–2e) could not be synthesized by microwave heating. Therefore, all these derivatives were synthesized using conventional Method C by oil bath heating, but the reaction took a very long time (22.5–88 h). To shorten the reaction time, we have developed Method D by oil bath heating with adding a phase transfer catalyst of Aliquat 336. In this method, we successfully shortened the reaction time from 88 h to 3 h for the synthesis of the derivative 2a. Thus, the reaction time for oil bath heating can be also greatly shortened by adding the phase transfer catalyst of Aliquat 336. Furthermore, we have established from POM, DSC and temperature-dependent X-ray diffraction measurements that the derivative C[Formula: see text]PcZn (1a) shows a very rare pseudohexagonal columnar (Col[Formula: see text] phase, and that the derivatives C[Formula: see text]PcZn (1b–1e) and C[Formula: see text](OH)PcZn (2b–2e) exhibit spontaneous perfect homeotropic alignment in a large area between two glass plates in their Col[Formula: see text] phases.

Microwave Synthesis of Silicon Carbide Nano Powders with Silicon and Carbon

2014 ◽  
Vol 602-603 ◽  
pp. 118-121
Author(s):  
You Jun Lu ◽  
Hong Fang Shen ◽  
Sheng Wei Guo
Keyword(s):  
Silicon Carbide ◽  
Particle Size ◽  
Microwave Heating ◽  
Chemical Reaction ◽  
Crystalline Phase ◽  
Microwave Synthesis ◽  
Time Effects ◽  
Xrd Patterns

Nanosized silicon carbide powders were synthesized from a mixture of silicon and carbon by microwave heating methods. The Result Indicates SiC can be formed at lower temperatures by using the Si-C reaction at 1200°C for 30min. XRD patterns shows that SiC peaks appeared as the only crystalline phase. SEM photo shows the particle size was 100～200 nanometer. At the same time, Effects of chemical reaction of silicon and carbon was researched by mechanical activated microwave synthesis.

scholarly journals Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

2013 ◽  
Vol 9 ◽  
pp. 467-475 ◽  
Author(s):  
Silvia M Soria-Castro ◽  
Alicia B Peñéñory
Keyword(s):  
Microwave Irradiation ◽  
Microwave Heating ◽  
Catalytic System ◽  
Low Cost ◽  
One Pot ◽  
Alkyl Aryl ◽  
One Pot Synthesis ◽  
Aryl Iodides ◽  
The One ◽  
Aryl Sulfides

S-aryl thioacetates can be prepared by reaction of inexpensive potassium thioacetate with both electron-rich and electron-poor aryl iodides under a base-free copper/ligand catalytic system. CuI as copper source affords S-aryl thioacetates in good to excellent yields, by using 1,10-phenanthroline as a ligand in toluene at 100 °C after 24 h. Under microwave irradiation the time was drastically reduced to 2 h. Both procedures are simple and involve a low-cost catalytic system. This methodology was also applied to the “one-pot” synthesis of target heterocycles, such as 3H-benzo[c][1,2]dithiol-3-one and 2-methylbenzothiazole, alkyl aryl sulfides, diaryl disulfides and asymmetric diaryl sulfides in good yields.

Synthesis of anti-inflammatory 2,3-unsaturated O-glycosides using conventional and microwave heating techniques

2017 ◽  
Vol 23 (3) ◽  
pp. 205-211
Author(s):  
Adriana Cristina N. de Melo ◽  
Ronaldo N. de Oliveira ◽  
João R. de Freitas Filho ◽  
Teresinha G. da Silva ◽  
Rajendra M. Srivastava
Keyword(s):  
Reaction Time ◽  
Microwave Irradiation ◽  
Microwave Heating ◽  
Acid Catalyst ◽  
Conventional Heating ◽  
Microwave Exposure ◽  
Ferrier Rearrangement ◽  
Acetyl Group ◽  
Anti Inflammatory

AbstractThe preparation of eight 2,3-unsaturated O-glycosides from D-glycals and alcohols, using montmorillonite K-10 as an acid catalyst, is described. The Ferrier rearrangement products were obtained in good yields using conventional heating and microwave irradiation but the reaction time was substantially reduced employing the latter procedure. The yields were slightly lower under microwave exposure. Five of the di-O-acetylated products were deacetylated to the glycosides in excellent yields. The acetylated products possess good anti-inflammatory property suggesting that the acetyl group plays an important role in reducing the inflammation. Among the compounds tested, glycosides containing thiophene as an aglycone present much better inflammation reducing characteristics than the analogues without this function.

Sign in / Sign up

Export Citation Format

Share Document