The influence of microwaves on the rate of reaction of propan-1-ol with ethanoic acid

Pollington, Stephen; Bond, Gary; Moyes, R.B.; Whan, David A.; Candlin, J. P.; Jennings, J. R.

doi:10.1021/jo00003a074

Cited by 62 publications

(29 citation statements)

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“…They showed that rate enhancements of 1.5 to 2 times were observed with heterogeneous catalysts whereas no rate enhancements were observed under homogeneous conditions. For example, the rate constants for the esterification of acetic acid with propanol in the presence of sulfuric acid (homogeneous conditions) under classical and MW heating at 80 8C were almost identical, as previously observed by Pollington et al [57]. On the other hand, when iron III sulfate with montmorillonite was used as the catalyst (heterogeneous conditions) the rate constant of the MW-heated reaction was twice that of the classically heated reaction.…”

Section: Comparison Of Homogeneous and Heterogeneous Conditionssupporting

confidence: 83%

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Organic Synthesis Using Microwaves in Homogeneous Media

Gedye

2002

Microwaves in Organic Synthesis

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Although the ability of microwaves (MW) to heat water and other polar materials has been known for half a century or more, it was not until 1986 that two groups of researchers independently reported the application of MW heating to organic synthesis. Gedye et al. [1] found that several organic reactions in polar solvents could be performed rapidly and conveniently in closed Teflon vessels in a domestic MW oven. These reactions included the hydrolysis of amides and esters to carboxylic acids, esterification of carboxylic acids with alcohols, oxidation of alkyl benzenes to aromatic carboxylic acids and the conversion of alkyl halides to ethers.Most of these reactions occurred much faster using MW irradiation (at increased pressure and temperature) than under conventional heating (ambient pressure, reflux), with rate enhancements ranging from 5 to 1200 times.Shortly after these results were published, Giguere and coworkers reported dramatic reductions in reaction times in other MW-assisted syntheses, including Diels± Alder, Claisen rearrangements and ene reactions [2]. These reactions were also performed at elevated pressures, but sealed glass vessels (inside a bath packed with vermiculite) were used rather than Teflon.It is to be noted that the reactions mentioned so far were performed under homogeneous conditions and, in most cases, using polar solvents, which are efficient absorbers of MW energy. Rate enhancements were attributed to the superheating of the solvent due to the elevated pressures generated in the closed vessels.During the 15 years since these reports, a large number of synthetic applications of MW in organic. synthesis have been reported and these have been summarized in a number of reviews [3±10].The use of dry media (solvent-free) conditions, in which the reactants are absorbed on inert solid supports, in MW-heated reactions, has received a considerable amount of attention recently and has been used in the synthesis of a wide range of compounds [11±16]. These reactions generally occur rapidly and the method avoids hazards, such as explosions, associated with reactions in solvents in sealed vessels in which high pressures may be generated. Also the removal of 115 Microwaves in Organic Synthesis. Edited by Andr Loupy

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Section: Comparison Of Homogeneous and Heterogeneous Conditionssupporting

confidence: 83%

“…Later, in a more carefully controlled comparison, Pollington et al [57] showed that the esterification of acetic acid with 1-propanol also occurred at the same rate under MW and conventional reflux.…”

Section: Reactions In Homogeneous Media Showing No Mw Rate Enhancementmentioning

confidence: 99%

Organic Synthesis Using Microwaves in Homogeneous Media

Gedye

2002

Microwaves in Organic Synthesis

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“…The main benefits of performing reactions under MI are the significant rateenhancement and the higher product yields. However, MI is generally not effective for organic synthesis at low temperature, while most microwave-assisted organic syntheses were carried out at high temperatures by using the thermal action of MI (Dollington et al, 1991;Cherng, 2002). To our knowledge, only few papers on organic syntheses under MI at low temperature have been reported.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature synthesis of allyl dimethylamine by selective heating under microwave irradiation used for water treatment

Tian

Zhang

2005

Radiation Physics and Chemistry

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Low-temperature synthesis of allyl dimethylamine (ADA) by selective heating under microwave irradiation (MI) used for water treatment is investigated. The effect of MI, ultrasound irradiation (UI) and conventional heating on yield of ADA, reaction time and the flocculation efficiency of polydiallyl dimethylammunion chloride (PDADMAC) prepared form ADA were studied. The results show that by selective heating at low temperature, MI not only increases yield of ADA and reduces reaction time, but also greatly enhances the flocculation efficiency of PDADMAC. r

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“…The influence of microwaves on the rate of esterification in the presence of solvents has been studied (7)(8)(9). A large acceleration of the reaction was observed in sealed Teflon vessels due to thermal and pressure effects.…”

Section: Acid Rcooh + R'oh Rcoor' + H20mentioning

confidence: 99%

“…W e have been concerned with microwave activation in "dry media" (4-6) and its application for synthetic and simplificative purposes to the preparation of esters, taking advantage of two possible specific effects: rate enhancements, essentially due to thermal effects (7)(8)(9)39) and displacements of equilibria by removal of volatile polar molecules (water or light alcohols).…”

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confidence: 99%