Microwave-Assisted Reactions in Organic Synthesis—Are There Any Nonthermal Microwave Effects?

Kuhnert, Nikolai

doi:10.1002/1521-3773(20020603)41:11<1863::aid-anie1863>3.0.co;2-l

Cited by 293 publications

(127 citation statements)

References 3 publications

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“…Heating with microwave was more efficient in terms of energy, homogen temperature and short time. Therefore, the main advantages of using the microwave were very short reaction time and high yield [24].…”

Section: Resultsmentioning

confidence: 99%

Microwave-Assisted Organic Reactions: Eco-friendly Synthesis of Dibenzylidenecyclohexanone Derivatives via Crossed Aldol Condensation

2017

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Keywords: dibenzylidenecyclohexanone; MAOS; eco-friendly ABSTRAK Telah dilakukan sintesis dibenzilidensikloheksanon dan turunannya melalui reaksi kondensasi aldol silang yang ramah lingkungan menggunakan metode MAOS. Sintesis dibenzilidensikloheksanon (8b) dilakukan melalui reaksi kondensasi antara benzaldehida 4 dan sikloheksanon 2 dalam krus porselen dengan rasio mol 2:1 menggunakan katalis natrium hidroksida selama 2 menit di dalam microwave. Turunan benzaldehida yang digunakan adalah 4-metoksibenzaldehida dan 3,4-dimetoksibenzaldehida untuk mensintesis (2E,6E)-bis(4-metoksibenziliden) siklo heksanon (8a) dan (2E,6E)-bis (3,4-dimetoksibenziliden)sikloheksanon (8c

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Section: Resultsmentioning

confidence: 99%

Microwave-Assisted Organic Reactions: Eco-friendly Synthesis of Dibenzylidenecyclohexanone Derivatives via Crossed Aldol Condensation

2017

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“…The "thermal" effects refer to interactions resulting in increased random motion of particles (e.g., atoms, molecules, ions, or electrons) where the kinetic energy statistics of such fluctuations are represented by a single thermodynamic equilibrium distribution (i.e., Maxwell-Boltzmann, Bose-Einstein, or Fermi-Dirac). "Non-thermal" effects refer to interactions resulting in non-equilibrium energy fluctuation distributions or deterministic, time-averaged drift motion of matter (or both) (Kuhnert, 2002;Booske et al, 1997). This provides the molecule collision under microwave irradiation extra driving force compared to that under conventional heating, which results in higher rate of reaction under mmicrowave irradiation as long as the enzyme is not deactivated by microwave.…”

Section: Resultsmentioning

confidence: 99%

Microwave Assisted Bioethanol Production from Sago Starch by Co-Culturing of Ragi Tapai and Saccharomyces Cerevisiae

Saifuddin¹,

Hussain

2011

Journal of Mathematics and Statistics

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Problem statement: Environmental issues such as global warming and recent events throughout the world, including the shortage of petroleum crude oil, the sharp increase in the cost of oil and the political instability of some crude oil producing countries, have demonstrated the vulnerability of the present sources for liquid fuel. These situations have created great demand for ethanol from fermentation process as green fuel. A main challenge in producing the ethanol is the production cost. A rapid and economical single step fermentation process for reliable production of bioethanol was studied by co-culturing commercialized ragi tapai with Saccharomyces cerevisae using raw sago starch. Approach: Enzymatic hydrolysis of sago starch by various amylolytic enzymes was investigated to reveal the potential coupling mechanism of Microwave Irradiation-Enzyme Coupling Catalysis (MIECC). Results: It was shown that enzymatic hydrolysis of starch using typical enzymes may successfully be carried out at microwave condition. The MIECC resulted in increasing initial reaction rate by about 2 times. The results testify on specific activation of enzymes by microwaves and prove the existence of non-thermal effect in microwave assisted reactions. Low power microwave irradiation (80W) does not increase the temperature beyond 40 o C and hence denaturation of the enzyme is avoided. The maximum ethanol fermentation efficiency was achieved (97.7% of the theoretical value) using 100 g L −1 sago starch concentration. The microwave assisted process improved the yield of ethanol by 45.5% compared to the non-microwave process. Among the other advantages of co-culturing of ragi tapai with S. cerevisiae is the enhancement of ethanol production and prevention of the inhibitory effect of reducing sugars on amylolytic activity and the reaction could be completed within 32±1 h. Conclusion: The present study have demonstrated the ability of using cheaply and readily ragi tapai for conversion of starch to glucose and the utilization of sago starch as a feed stock, which is cheaper than other starches like corn and potato. The present study has highlighted the importance of well controlled microwave assisted enzymatic reaction to enhance the overall reaction rate of the process.

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“…The possibility of nonthermal effect of microwaves on the different processes and substances, despite the considerable amount of experimental work, is the subject of lively debate recently [2,5,6]. The mechanism of this influence is not entirely clear.…”

Section: Introductionmentioning

confidence: 99%

Long-Term Structural Modification of Water under Microwave Irradiation: Low-Frequency Raman Spectroscopic Measurements

Yakunov

Biliy

Naumenko

2017

Advances in Optical Technologies

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Raman scattering has been used to study the influence of 2.45 GHz microwave on the structure of water. It has been shown that treatment of the distilled water samples by electromagnetic field leads to long-term changes in the vibrational density of states. It was established that the retention time of structural changes of the water samples depends on the sample volume. The experimental results have been interpreted on the basis of the percolation model. It has been suggested that the change in the chemical composition of the water treated by microwaves can lead to a change in the structure of the percolation cluster formed by the network of hydrogen bonds. The time of the equilibrium structure recovery of the percolation cluster after termination of the microwaves depends on the cluster size and is much slower than the recovery in the chemical composition of water.

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Microwave-Assisted Reactions in Organic Synthesis—Are There Any Nonthermal Microwave Effects?

Cited by 293 publications

References 3 publications

Microwave-Assisted Organic Reactions: Eco-friendly Synthesis of Dibenzylidenecyclohexanone Derivatives via Crossed Aldol Condensation

Microwave-Assisted Organic Reactions: Eco-friendly Synthesis of Dibenzylidenecyclohexanone Derivatives via Crossed Aldol Condensation

Microwave Assisted Bioethanol Production from Sago Starch by Co-Culturing of Ragi Tapai and Saccharomyces Cerevisiae

Long-Term Structural Modification of Water under Microwave Irradiation: Low-Frequency Raman Spectroscopic Measurements

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