Table Of ContentNONTRADITIONAL
ACTIVATION METHODS
IN GREEN AND
SUSTAINABLE
APPLICATIONS
Advances in Green and Sustainable
Chemistry
NONTRADITIONAL
ACTIVATION METHODS IN
GREEN AND SUSTAINABLE
APPLICATIONS
Microwaves; Ultrasounds; Photo-,
Electro- and Mechanochemistry and
High Hydrostatic Pressure
Series Editor
(cid:1) € €
BELA TOROK
Professor, University of Massachusetts Boston, Boston, MA,
United States
€
CHRISTIAN SCHAFER
Lecturer, University of Massachusetts Boston, Boston, MA,
United States
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Contributors
RicardoBelloso
DepartmentofChemistry,GeorgiaSouthernUniversity,Statesboro,GA,UnitedStates
ClarenceCharnay
ICGM,UnivMontpellier,CNRS,ENSCM,Montpellier,France
PedroCintas
DepartmentofOrganicandInorganicChemistry,FacultyofSciencesandIACYS-GreenChemistry
andSustainableDevelopmentUnit,UniversityofExtremadura,Badajoz,Spain
EvelinaColacino
ICGM,UnivMontpellier,CNRS,ENSCM,Montpellier,France
GiancarloCravotto
DepartmentofDrugScienceandTechnology,andNIS-CentreforNanostructuredInterfacesandSurfaces,
UniversityofTurin,Turin,Italy
FrancescoDelogu
DipartimentodiIngegneriaMeccanica,Chimica,edeiMateriali,Universita`degliStudidiCagliari,Cagliari,
Italy
FranziskaEmmerling
BAMFederalInstituteforMaterialsResearchandTesting,Berlin,Germany
SatoshiFujii
DepartmentofInformationandCommunicationSystemEngineering,OkinawaCollege,Okinawa,Japan
AharonGedanken
DepartmentofChemistry,BarIlanUniversity,RamatGan,Israel
AllenGordon
DepartmentofChemistryandBiochemistry,GeorgiaSouthernUniversity,Statesboro,GA,UnitedStates
NorbertHoffmann
CNRS,Universit(cid:1)edeReimsChampagne-Ardenne,ICMR,EquipedePhotochimie,UFRSciences,
Reims,France
Istva´nJablonkai
MTATTKLendu¨letFunctionalOrganicMaterialsResearchGroup,InstituteofOrganicChemistry,Research
CentreforNaturalSciences,Budapest,Hungary
AnkeKabelitz
BAMFederalInstituteforMaterialsResearchandTesting,Berlin,Germany
AttilaKunfi
MTATTKLendu¨letFunctionalOrganicMaterialsResearchGroup,InstituteofOrganicChemistry,Research
CentreforNaturalSciences,Budapest,Hungary
ShainazLandge
DepartmentofChemistryandBiochemistry,GeorgiaSouthernUniversity,Statesboro,GA,UnitedStates
CorentinLefebvre
CNRS,Universit(cid:1)edeReimsChampagne-Ardenne,ICMR,EquipedePhotochimie,UFRSciences,
Reims,France
xi
xii Contributors
Ga´borLondon
MTATTKLendu¨letFunctionalOrganicMaterialsResearchGroup,InstituteofOrganicChemistry,Research
CentreforNaturalSciences,Budapest,Hungary
KatiaMartina
DepartmentofDrugScienceandTechnology,andNIS-CentreforNanostructuredInterfacesandSurfaces,
UniversityofTurin,Turin,Italy
AdamA.L.Michalchuk
BAMFederalInstituteforMaterialsResearchandTesting,Berlin,Germany
ManishaMishra
DepartmentofChemistry,UniversityofMassachusettsBoston,Boston,MA,UnitedStates
TaraMooney
DepartmentofChemistry,UniversityofMassachusettsBoston,Boston,MA,UnitedStates
MariaJesusMoran
DepartmentofDrugScienceandTechnology,andNIS-CentreforNanostructuredInterfacesandSurfaces,
UniversityofTurin,Turin,Italy
BilalNi¸sancı
DepartmentofChemistry,FacultyofScience,Atatu€rkUniversity,Erzurum,Turkey
Istva´nPa´linko´
UniversityofSzeged,Szeged,Hungary
AndreaPorcheddu
DipartimentodiScienzeChimicheeGeologiche,Universita`degliStudidiCagliari,CittadellaUniversitaria,
Monserrato,CA,Italy
IndraNeelPulidindi
DepartmentofChemistry,BarIlanUniversity,RamatGan,Israel
Da-HuiQu
KeyLaboratoryforAdvancedMaterials,SchoolofChemistryandMolecularEngineering,EastChina
UniversityofScienceandTechnology,Shanghai,China
ChristianSch€afer
DepartmentofChemistry,UniversityofMassachusettsBoston,Boston,MA,UnitedStates
AbidShaikh
DepartmentofChemistry,GeorgiaSouthernUniversity,Statesboro,GA,UnitedStates
Pa´lSipos
UniversityofSzeged,Szeged,Hungary
Ma´rtonSzabados
UniversityofSzeged,Szeged,Hungary
B(cid:1)elaTo€ro€k
DepartmentofChemistry,UniversityofMassachusettsBoston,Boston,MA,UnitedStates
ShuntaroTsubaki
SchoolofMaterialsandChemicalTechnology,TokyoInstituteofTechnology,Yokohama,Japan
Ga´borVarga
UniversityofSzeged,Szeged,Hungary
Contributors xiii
YujiWada
InstituteofInnovationResearch,TokyoInstituteofTechnology,Yokohama;MicrowaveChemicalCo.Ltd.,
TechnoAlliance3F,Suita,Osaka,Japan
KazutakaYamamoto
HeadofLaboratory,FoodProcessEngineering,DivisionofFoodProcessingandDistribution,FoodResearch
Institute,NationalAgricultureandFoodResearchOrganization,Tsukuba,Ibaraki,Japan
CHAPTER ONE
Application of nontraditional
activation methods in green and
sustainable chemistry:
Microwaves, ultrasounds, electro-,
photo-, and mechanochemistry,
and high hydrostatic pressure
Christian Sch€afer and Be(cid:2)la To€ro€k
DepartmentofChemistry,UniversityofMassachusettsBoston,Boston,MA,UnitedStates
1 Introduction
Many discoveries made in chemistry in the 20th century enabled
strong developments in the preparation of a broad range of products. The
developingchemicalindustrywasmostlybasedonpetroleumresourcesthat
provided a steady flow of raw materials. The continuous development of
new fields such as medicinal chemistry, polymers and plastics, agrochemi-
cals, and the likes resulted in booming industrial production. Although
the new products had a largely positive impact on the society as a whole,
several unintended issues began to appear. These included industrial disas-
ters, drug side effects, and the damage caused to Earth’s protective ozone
layer among many others. These incidents made the society realize the
potential harmful effects of large-scale production and the associated waste
producedbyit,someproductsthemselves,andtheinabilityoftheseproducts
todecomposeattheendoftheirlifecycle.Inaddition,theextensiveuseof
fossil fuels for energy production and petroleum derivatives for industrial
feedstockresultedinissuesthatcanfurtherthreatentheplanet’secosystem.
While there have been corrective measures implemented along the way in
theformsofgovernmentregulations,aconcentratedeffortinthelate1990s
resultedinthebirthoftheGreenChemistrymovement1toaddressthefun-
damentalnatureoftheproblems.Infact,thecurrenteffortsoftenappearto
bejointventuresbygovernment,academia,andindustrysuggestingamuch
NontraditionalActivationMethodsinGreenandSustainableApplications ©2021ElsevierInc. 1
https://doi.org/10.1016/B978-0-12-819009-8.00016-5 Allrightsreserved.
2 ChristianSch€aferandB(cid:2)elaTo€ro€k
more effective tackling of the problems than when these entities were
activelyworkingagainsteachotherdelayingthedevelopmentofactualsolu-
tions. This ongoing partnership ensures the continuous expansion and
advancement of environmentally friendly processes and products,2–4 and
green chemistry and environmental science made steady developments in
the general science education as well.5–7 There are many ways chemistry
cancontributetotheseadvances,replacingoldoutdatedchemicalprocesses
with ones having less environmental impact, traditional petroleum based
rawmaterialswithsustainableones,ornotoriouslystableconventionalplas-
tics and other chemicals with biodegradable alternatives.
Thisintroductorychapterandtheentirebookfocusonaspecialtoolset
that is a great contributor to the development of green synthetic methods;
the so-called nontraditional activation methods that use alternative energy
forms to conventional convective heating to initiate chemical reactions.
A large majority of chemical reactions require activation energy in order
to occur. Traditionally this energy was introduced to a reaction as heat
mostlyviaconvectiveheatingusinganexternalheatsource.Althougheffec-
tive,convectiveheatingisslowandessentiallydependentonheatdiffusion
(mixing)inthesystem.Anotherproblemisthatthetemperatureofthewall
ofthereactionvesseliscommonly10–20°Chigherthanthatinthecenterof
the liquid, often causing side reactions or decomposition on or around the
surfaceofthewall.Toalleviatetheseissues,severalnontraditionalactivation
methods have been developed. Although different in nature, the common
featureofthesemethodsisthattheyarebasedonthedirectenergytransferin
the reaction mixture. In this chapter, we will only attempt to describe the
basic features of these methods, such as microwave- and ultrasonic irradia-
tion,photo-,electro-andmechanochemistryandhighhydrostaticpressure
withafewrepresentativeexamples,whichwillbefollowedbystate-of-the-
art specific applications in the upcoming chapters.
2 Microwave-assisted organic synthesis
Thefirstobservationsofthemicrowaveheatingeffectoccurredinthe
1940s when the magnetron, now the common microwave source, was
appliedduringthedevelopmentoftheRADAR.Followingupontheorig-
inal discovery the application of microwave ovens in the food and airline
industry began in the 1950s.8 Although the first synthetic application in
19699 largely went unnoticed, the independent publication of
microwave-activated synthetic applications by two teams, Gedye et al.10
Applicationofnontraditionalactivationmethods 3
and Giguere et al.11 initiated an exponential development of microwave-
assisted synthesis. Since then microwave-assisted organic synthesis
(MAOS) has become a household name in laboratories, with thousands
ofpaperspublishedinthisarea.Thecontemporarymicrowaveinstruments
and reactors provide the essential elements that are required in synthetic
chemistry, such as temperature control, reliability, reproducibility, and in
special cases, scalability. The theories of how microwaves interact with
materialshavebeenasubjectofasometimesintensedebate12–14andnumer-
ousreports,andreviews.15–17Here,weonlyfocusonthebasicinformation
related to this issue.
Thefrequencyrangeformicrowaveradiationisbetween1and300GHz
appearing in the relatively low energy region of the electromagnetic spec-
trum.Microwavespossesslowerenergythaninfraredirradiation,buthigher
than radio waves. Given their limited energy, microwave irradiation is not
able to excite electron transitions, break chemical bonds, or even activate
changes within individual molecules such as vibration. The rotational
motion of molecules is the physical phenomenon that microwave energy
can excite to generate internal heat formation. This entails that the micro-
waveeffectislimited toliquids andsolids.Although,gaseous materialscan
absorbmicrowaves,duetothelimitedinteractionbetweenthemoleculesit
doesnotgenerateheat,ratherresultsinsharppeaksinafingerprintfashion,
which is the foundation of microwave spectroscopy. In more dense mate-
rials, the rotating molecules will collide with each other, and due to the
restricted movement, dielectric polarization will occur, which is the major
source of microwave heating. Particularly two features, the dielectric con-
stant (ε0) and dielectric loss (ε00), and their ratio, the so-called loss tangent
delta (tgδ¼ε00/ε0) are important to determine how a certain compound
or material is able to convert the microwave irradiation to heat. Materials
of significant dipole moments (polar solvents, salts, ionic liquids, certain
metal oxides, etc.) are the best media for microwave-assisted chemistry.
Nonpolar materials (hydrocarbons and most plastics) are weak microwave
absorbers(orcompletelytransparent)andthusdonotgenerateinternalheat
formation.
Although the application of microwave irradiation as an activation
method carries multiple benefits, the major advantages are rapid reactions,
and therefore significantly reduced reaction times. This could be quitesig-
nificant; in our experience for example, the condensation of
trifluoroacetophenones with a variety of benzylamines require 168h
(1week!)heatingat130°C,whilethesamereactionheatedbymicrowaves
