Microwave Effect on Fischer Esterification

Koshima, Hideko; Miyazaki, Kensuke; Ishii, Saori; Asahi, Toru

doi:10.1246/cl.160067

Cited by 7 publications

(5 citation statements)

References 20 publications

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“…The most popular method used for stearate synthesis is based on the Fisher reaction, which consists of a reaction between a carboxylic acid and an alcohol (in molar excess) in the presence of an acid catalyst such as sulfuric acid, hydrochloric acid or p -toluensulfonic acid ( Figure 1 ) [ 9 , 10 , 11 ]. The reaction is performed in conventional reflux conditions (1–4 h) using benzene as a solvent and achieves yields from 58% to 75% [ 12 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

Lipase-Assisted Synthesis of Alkyl Stearates: Optimization by Taguchi Design of Experiments and Application as Defoamers

Olvera-Ureña,

Lopez-Tellez,

Vizueto

et al. 2023

Molecules

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The present work proposes the optimization of enzymatic synthesis of alkyl stearates using stearic acid, alkyl alcohols (C1-OH, C2-OH, C4-OH, C8-OH and C16-OH) and Candida rugosa lipase by a L9 (34) Taguchi-type design of experiments. Four variables were evaluated (reaction time, temperature, kU of lipase and alcohol:stearic acid molar ratio), ensuring that all variables were critical. In optimal conditions, five stearates were obtained with conversions > 90%. The obtained products were characterized by nuclear magnetic resonance (NMR). Additionally, the defoaming capacity of the five stearates was evaluated, obtaining better performance for the compound synthesized from C8-OH alcohol.

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Section: Introductionmentioning

confidence: 99%

Lipase-Assisted Synthesis of Alkyl Stearates: Optimization by Taguchi Design of Experiments and Application as Defoamers

Olvera-Ureña,

Lopez-Tellez,

Vizueto

et al. 2023

Molecules

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“…Similarly, it is reported that the heating method is another critical factor that affects esterification reaction rate and efficiency with respect to reactant conversion as well as desired product selectivity. 18 The fundamental of microwave heating lies in the fact that the microwave radiation heats only solvents and reactants without heating the wall of the vessel while passing through it. 19 On the contrary, a conventional heating system transfers heat via conduction and convection which also heats the wall of the vessel, thus a slow heating rate.…”

Section: Introductionmentioning

confidence: 99%

“…Koshima and co-workers studied the effects of microwave irradiations and conventional heating system using a quartz vessel and a silicon carbide vessel in the microwave reactor. 18 The authors noticed improvement in the ester yield when experiments were performed in a quartz vessel, which allows passage of microwaves, as compared to experiments performed in the silicon carbide, which reportedly does not allow microwaves to pass. However, complete absorption of all the microwaves in the silicon carbide vessel is not possible, and thus the possibility of microwaves passing partially into the reaction mixture cannot be ruled out.…”

Section: Introductionmentioning

confidence: 99%

“…However, a detailed study on LA esterification and parameters optimization is yet to be done for the effects of unsupported silicotungstic acid catalyst. Similarly, it is reported that the heating method is another critical factor that affects esterification reaction rate and efficiency with respect to reactant conversion as well as desired product selectivity . The fundamental of microwave heating lies in the fact that the microwave radiation heats only solvents and reactants without heating the wall of the vessel while passing through it .…”

Section: Introductionmentioning

confidence: 99%

“…However, uniform heat distribution through a heating mantle to the water bath is complex and challenging, and thus a comparative study was needed for further validation using a setup with more similarity and resemblance to a microwave reactor. Koshima and co-workers studied the effects of microwave irradiations and conventional heating system using a quartz vessel and a silicon carbide vessel in the microwave reactor . The authors noticed improvement in the ester yield when experiments were performed in a quartz vessel, which allows passage of microwaves, as compared to experiments performed in the silicon carbide, which reportedly does not allow microwaves to pass.…”

Section: Introductionmentioning

confidence: 99%

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Insights into the Synthesis of Ethyl Levulinate under Microwave and Nonmicrowave Heating Conditions

Ahmạd

Alam

Pant

et al. 2019

Ind. Eng. Chem. Res.

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The effects of microwave and nonmicrowave heating methods on the synthesis of ethyl levulinate (EL) from levulinic acid (LA) have been investigated in the present study. The levulinic acid esterification experiments were performed in the presence of silicotungstic acid catalyst and ethanol in a microwave and nonmicrowave instant heating reactor. An experimental fit of experimental data in a kinetic model suggested that LA esterification follows a pseudo-first-order reaction mechanism. Consequently, activation barriers were calculated (44–45 kJ/mol) and a negligible difference was found for LA esterification reaction performed in both the reactors. Nevertheless, slightly higher LA conversions were measured under microwave irradiations as compared to experiments performed in a nonmicrowave instant heating reactor. Thus, series of experiments were performed to study the (i) nonthermal and (ii) thermal effects of microwave heating irradiations. Eventually, it was found that the enhanced LA conversion in microwave reactor could be due improved heat transfer into the reaction mixture owing to direct heating by microwaves, as compared to conventional conductive and convective heat transfer in the instant heating reactor. In addition, experiments performed under different operating conditions such as at varying stirring speed, varying sample volume, and different catalyst concentration and reactant concentration indicated the absence of nonthermal microwave effects.

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Microwave Heating Outperforms Conventional Heating for a Thermal Reaction that Produces a Thermally Labile Product: Observations Consistent with Selective Microwave Heating

Duangkamol

Batsomboon

Stiegman

et al. 2019

Chemistry An Asian Journal

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Microwave( MW) heatingi sm ore effective than conventional (CONV)h eating for promoting ah igh-temperature oxidative cycloisomerization reaction that was previously reported as ak ey step in at otal synthesis of the naturalp roduct illudinine.T he thermal reaction pathway as envisioned is an inverse electron-demand dehydro-Diels-Alder reaction with in situ oxidation to generate as ubstituted isoquinoline, which itself is unstablet ot he reaction conditions. Observed reaction yields were higher at am easured bulk temperature of 200 8Ct han at 180 8C or 220 8C; at 24 hours than at earliero rl ater time points; and when the reaction solution was heatedu sing MW energy as opposedt oC ONV heating with am etal heat block. Selective MW heating of polar solutea ggregates is postulated to explain these observations. We recently reported as ynthesis of illudinine [1] in conjunction with broader efforts to produce targets of interestb earing neopentylene ring fusions. [2] Previously reported syntheses of illudinine required 14 [3] to 16 [4] steps, many of which were dedicated to craftingt he neopentylene ring fusion. Our reported synthesis of illudinine featured tandem fragmentation and olefination methodology from our lab, [5] and it was relativelye fficient, providings ynthetic illudinine in 8steps and 14 %o verall yield from commerciallyavailable dimedone (Scheme 1).Our synthesis of illudinine featured ak ey oxidative cycloisomerization (Scheme 2). Related oxidative cycloisomerizations of styrenes have been reported recently, [6] along with evidence that they proceed by way of an intramolecular Diels-Alder (IMDA) cycloadditionf ollowed by concerted extrusion of molecular hydrogen. [6b] We built from this work to examine inverse electron-demand vinylpyridine Diels-Alders ubstrates (e.g., 1), finding that the bromoalkyne( as opposed to the terminal alkyne) was necessary for cycloisomerization to outcom-pete general decomposition in the reaction mixture. The 40 % yield of isoquinoline 2 that we observedw as sufficient to advance materialthrough to the final target, but it was the weakest link in our chain of synthetic reactions.Here we report ar e-examinationo ft his reaction, paying particular attention to any differences between microwave (MW) and conventional (CONV) heating. [7] In contrast to the 40 % yield we reported using MW heating( Scheme 2), CONV heating produced isoquinoline 2 in only 15 %y ield after 12 hours. The yield of 2 increased to 39 %a fter 24 hours of CONV heating, but it diminished to 23 %a fter 36 hours. These observations gave us cause for concern that the isoquinoline product was not stable to the high-temperature reactionc onditions. We confirmed the thermal instability of isoquinoline 2 by heating it at 220 8Ci n1 ,2-dichlorobenzene and monitoring its disappearanceo ver time as it decomposed into ac omplex mixture of unidentified products (Table 1).In total, we examined three reaction temperatures (180 8C, 200 8C, and 220 8C) at varioust ime-points using both MW and CONV heating (Table 2). Twot...

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Microwave Effect on Fischer Esterification

Cited by 7 publications

References 20 publications

Lipase-Assisted Synthesis of Alkyl Stearates: Optimization by Taguchi Design of Experiments and Application as Defoamers

Lipase-Assisted Synthesis of Alkyl Stearates: Optimization by Taguchi Design of Experiments and Application as Defoamers

Insights into the Synthesis of Ethyl Levulinate under Microwave and Nonmicrowave Heating Conditions

Microwave Heating Outperforms Conventional Heating for a Thermal Reaction that Produces a Thermally Labile Product: Observations Consistent with Selective Microwave Heating

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