Nonthermal Effects of Microwaves in Organic Synthesis

This critical review examines recent scientific and patent literature in the application of microwave reactors for catalytic transformation of biomass and biomass-derived molecules with a particular emphasis on heterogeneous catalysis. Several recent reports highlight dramatic reductions in reaction time and even superior selectivity when microwaves are used. However, there are still many controversies and unexplained effects in this area that deserve attention. We critically review the available sources attempting to establish trends and elucidate the actual status of this area of research. Additionally, where possible, we discuss the potential for scale-up and commercial utilization of microwaves and impediments that currently hold back their implementation. This critical review aims at highlighting the opportunity of combining catalysis with microwave technology for biomass conversion but also to stimulate the reader to generate future understanding of the influence of the microwaves in catalytic processes in general.

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“…In Microwaves in Organic Synthesis ; de la Hoz, A., Loupy, A., Eds. ; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, 2013 …”

Section: Thermal Vs Nonthermal Microwave Effectmentioning

confidence: 99%

Advantages and Limitations of Microwave Reactors: From Chemical Synthesis to the Catalytic Valorization of Biobased Chemicals

Priecel

López-Sánchez

2018

ACS Sustainable Chem. Eng.

198

101

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“…Application of MW in organic synthesis is considered as a "green" approach because this frequently permits improving efficiency of the reactions. 19 This technique has been extended to the polycondensation polymers. 21 Syntheses of PBIs by solution polycondensation in PPA using MW have also been reported.…”

Section: Preparation Of Opbi and Cf 3 Pbi Using Mwmentioning

confidence: 99%

“…In recent years, the microwave techniques have been increasingly employed in organic synthesis because it allows increasing the synthesis efficiency and shortening the reaction time. 19 Synthesis of high performance polymers under microwave irradiation (MW) has also been reported. [20][21][22][23] In general, use of MW resulted in an acceleration of the polymerizations and even promoted the formation of polymers with higher molecular weights.…”

Section: Introductionmentioning

confidence: 99%

Eaton’s reagent in polybenzimidazole synthesis

Olvera‐Mancilla

Palacios‐Alquisira

Alexandrova

2017

High Performance Polymers

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The polycondensations of 3,3′-diaminobenzidine with two acids, 4,4′-oxybis(benzoic acid) and hexafluoroisopropylidene bis(benzoic acid), were conducted in Eaton’s reagent at the unusually high temperature of 180°C and under microwave irradiation at 90°C. Both protocols resulted in soluble polybenzimidazoles, OPBI and CF3PBI, of high molecular weights in very short reaction times. The synthesized polybenzimidazoles exhibited high thermostability and excellent mechanical properties. The influence of the reaction conditions on the polymer structure and molecular weights was studied. The “microwave effect” was demonstrated by comparison of the polycondensations conducted under microwave irradiation and conventional heating.

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“…[ 29 ] Microwave transparent solvents can even be advantageous because they allow a specific absorption by the reactants. [ 30 ] Indeed, microwave irradiation of chalcone 11aa in toluene at 250 °C for 1 h resulted in the formation of 12aa and 13aa in a ratio of 0.8:1.0 and a combined yield of 93 % (entry 11), which is even higher than the yield obtained in N,N ‐DEA under otherwise identical conditions (entry 1). Addition of NaOAc did not improve the yield of the flavanone (entry 12).…”

Section: Resultsmentioning

confidence: 97%