Combustion-derived CuO nanoparticles: An effective and environmentally benign catalyst in the synthesis of aromatic nitriles from aromatic aldehydes

Article abstract of DOI:10.1016/S1872-2067(11)60503-2

CuO nanoparticles were synthesized using an energy-efficient and rapid solution combustion technique with malic acid employed as a fuel. The combustion-derived CuO nanoparticles were used as catalysts in a one-pot synthesis of aromatic nitriles from aromatic aldehydes and hydroxylamine hydrochloride. The catalyst was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, transmission electron microscopy, and Brunauer-Emmett-Teller surface area analysis. The catalytic activity of the CuO nanoparticles in the synthesis of aromatic nitriles from aromatic aldehydes was evaluated. The present protocol offers the advantages of a clean reaction, simple methodology, short reaction duration (1-2 min), and high yield (85%-98%). The catalytic activity of the CuO nanoparticles was found to be higher than that of bulk CuO powder under the same conditions. The catalyst can also be recovered and reused up to four times with no significant loss of catalytic activity. The present approach is inexpensive and is a convenient technique suitable for industrial production of CuO nanoparticles and nitriles.

Full text of DOI:10.1016/S1872-2067(11)60503-2

ChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ704–710
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ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
ava i l a b l e a t w w w. s c i e n c ed i r e c t . c o m
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j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e /c h n j c
ꢀ
ꢀ
Article
Combustion‐derivedꢀCuOꢀnanoparticles:ꢀAnꢀeffectiveꢀandꢀ ꢀ
environmentallyꢀbenignꢀcatalystꢀinꢀtheꢀsynthesisꢀofꢀaromaticꢀnitrilesꢀ
fromꢀaromaticꢀaldehydesꢀ
ꢀ
a
ꢀa
BelladamaduꢀSiddappaꢀANANDAKUMAR ,ꢀMuthukurꢀBhojegowdꢀMadhusudanaꢀREDDY ,ꢀ ꢀ
ꢀb
ꢀa
ꢀa,
ChikkaꢀNagaiahꢀTHARAMANI ,ꢀMohamedꢀAfzalꢀPASHA ,ꢀGujjarahalliꢀThimmannaꢀCHANDRAPPA *
ꢀ
aꢀDepartmentꢀofꢀChemistry,ꢀBangaloreꢀUniversity,ꢀBangalore‐560001,ꢀIndiaꢀ ꢀ
bꢀDepartmentꢀofꢀChemistry,ꢀRuhrꢀUniversitätꢀBochum,ꢀBochum,ꢀGermanyꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
CuOꢀnanoparticlesꢀwereꢀsynthesizedꢀusingꢀanꢀenergy‐efficientꢀandꢀrapidꢀsolutionꢀcombustionꢀtech‐
niqueꢀwithꢀmalicꢀacidꢀemployedꢀasꢀaꢀfuel.ꢀTheꢀcombustion‐derivedꢀCuOꢀnanoparticlesꢀwereꢀusedꢀas
catalystsꢀinꢀaꢀone‐potꢀsynthesisꢀofꢀaromaticꢀnitrilesꢀfromꢀaromaticꢀaldehydesꢀandꢀhydroxylamine
hydrochloride.ꢀTheꢀcatalystꢀwasꢀcharacterizedꢀbyꢀX‐rayꢀdiffraction,ꢀscanningꢀelectronꢀmicroscopy,
energy‐dispersiveꢀX‐rayꢀ analysis,ꢀ transmissionꢀ electronꢀmicroscopy,ꢀandꢀBrunauer‐Emmett‐Tellerꢀ
surfaceꢀareaꢀanalysis.ꢀTheꢀcatalyticꢀactivityꢀofꢀtheꢀCuOꢀnanoparticlesꢀinꢀtheꢀsynthesisꢀofꢀaromatic
nitrilesꢀ fromꢀ aromaticꢀaldehydesꢀ wasꢀevaluated.ꢀ Theꢀpresentꢀprotocolꢀoffersꢀtheꢀadvantagesꢀofꢀa
cleanꢀreaction,ꢀsimpleꢀmethodology,ꢀshortꢀreactionꢀdurationꢀ(1–2ꢀmin),ꢀandꢀhighꢀyieldꢀ(85%–98%).
TheꢀcatalyticꢀactivityꢀofꢀtheꢀCuOꢀnanoparticlesꢀwasꢀfoundꢀtoꢀbeꢀhigherꢀthanꢀthatꢀofꢀbulkꢀCuOꢀpowder
underꢀtheꢀsameꢀconditions.ꢀTheꢀcatalystꢀcanꢀalsoꢀbeꢀrecoveredꢀandꢀreusedꢀupꢀtoꢀfourꢀtimesꢀwithꢀno
significantꢀlossꢀofꢀcatalyticꢀactivity.ꢀTheꢀpresentꢀapproachꢀisꢀinexpensiveꢀandꢀisꢀaꢀconvenientꢀtech‐
niqueꢀsuitableꢀforꢀindustrialꢀproductionꢀofꢀCuOꢀnanoparticlesꢀandꢀnitriles.ꢀ
Receivedꢀ31ꢀAugustꢀ2012ꢀ
Acceptedꢀ3ꢀDecemberꢀ2012ꢀ
Publishedꢀ20ꢀAprilꢀ2013ꢀ
Keywords:ꢀ
Copperꢀoxideꢀ
Nanoparticleꢀ
Solutionꢀcombustionꢀ
Nitrileꢀ
Aldehydeꢀ
Hydroxylꢀamine
©ꢀ2013,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1
.ꢀ ꢀ Introductionꢀ
catalystsꢀforꢀorganicꢀsynthesisꢀ[2–5].ꢀThereꢀhaveꢀthusꢀfarꢀbeenꢀ
numerousꢀ methodsꢀ developedꢀ forꢀ theꢀ preparationꢀ ofꢀ copperꢀ
oxideꢀ NPs,ꢀ includingꢀ viaꢀ solid‐stateꢀ reactionsꢀ [6];ꢀ sol‐gelꢀ [7],ꢀ
sonochemicalꢀ [8],ꢀ solvothermal,ꢀ alcohothermalꢀ [9],ꢀ hydro‐
thermalꢀ[10],ꢀandꢀvaporꢀdepositionꢀtemplateꢀmethodsꢀ[11];ꢀwetꢀ
chemistryꢀ routesꢀ [12];ꢀ andꢀ alkoxide‐basedꢀ preparationsꢀ [13].ꢀ
Allꢀ ofꢀ theseꢀ methodsꢀ requireꢀ expensiveꢀ precursorsꢀandꢀ highꢀ
temperatures,ꢀ areꢀ time‐consuming,ꢀ andꢀ consumeꢀ significantꢀ
amountsꢀofꢀenergyꢀforꢀcompletion.ꢀHowever,ꢀamongꢀtheꢀmeth‐
odsꢀ reportedꢀ inꢀ theꢀ literature,ꢀ solutionꢀ combustionꢀ (SC)ꢀ hasꢀ
provedꢀoneꢀofꢀtheꢀmoreꢀsuccessfulꢀmethodsꢀforꢀtheꢀsynthesisꢀofꢀ
metalꢀoxideꢀNPsꢀandꢀthisꢀmethodꢀisꢀrelativelyꢀsimpleꢀandꢀenvi‐
ronmentallyꢀ benign.ꢀ Theꢀ advantagesꢀ ofꢀ thisꢀ methodꢀ overꢀ theꢀ
Theꢀadvancedꢀpropertiesꢀofꢀnanoscaleꢀmetalꢀoxideꢀparticlesꢀ
haveꢀ encouragedꢀwide‐rangingꢀ researchꢀ activityꢀ onꢀtheirꢀ ap‐
plicationꢀinꢀelectronics,ꢀoptics,ꢀandꢀcatalysisꢀ[1].ꢀWithinꢀtheꢀfieldꢀ
ofꢀ greenꢀ chemistry,ꢀ nanometalꢀ oxideꢀ catalyzedꢀ reactionsꢀ areꢀ
recognizedꢀ asꢀ beingꢀ attractiveꢀ andꢀ environmentallyꢀ benignꢀ
methodsꢀ ofꢀ organicꢀ synthesis.ꢀ Amongꢀ theꢀ knownꢀ varietiesꢀofꢀ
metalꢀoxides,ꢀcopperꢀoxideꢀnanoparticlesꢀ(NPs)ꢀpossessꢀuniqueꢀ
physicochemicalꢀ propertiesꢀ suchꢀ asꢀsmallꢀ particleꢀ size,ꢀ largeꢀ
surfaceꢀ area,ꢀ andꢀ unusualꢀ reactiveꢀ morphologyꢀ andꢀ surfaceꢀ
activeꢀ sites.ꢀ Inꢀ additionꢀ toꢀ theirꢀ highꢀ thermalꢀ stability,ꢀ strongꢀ
basicꢀcharacteristicsꢀmeanꢀthatꢀcopperꢀoxideꢀNPsꢀareꢀpromisingꢀ
*ꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+91‐80‐22961350;ꢀE‐mail:ꢀgtchandrappa@yahoo.co.inꢀ ꢀ ꢀ
ThisꢀworkꢀwasꢀsupportedꢀbyꢀUniversityꢀGrantꢀCommission,ꢀIndia.ꢀ
DOI:ꢀ10.1016/S1872‐2067(11)60503‐2ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ34,ꢀNo.ꢀ4,ꢀAprilꢀ2013ꢀ

ꢀ
BelladamaduꢀSiddappaꢀANANDAKUMARꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ704–710ꢀ
ꢀ
synthesisꢀ approachesꢀmentionedꢀvideꢀ supraꢀareꢀshorterꢀreac‐
tionꢀtimeꢀ(<ꢀ5ꢀmin),ꢀlowerꢀcostꢀ(withꢀtheꢀpotentialꢀtoꢀscaleꢀup),ꢀ
andꢀtheꢀpossibilityꢀofꢀusingꢀaꢀone‐potꢀsynthesis.ꢀInꢀadditionꢀtoꢀ
this,ꢀ theꢀ SCꢀ methodꢀ isꢀ usefulꢀ forꢀ producingꢀ homogenous,ꢀ po‐
rous,ꢀ andꢀ fineꢀ crystallineꢀ powdersꢀ [14].ꢀ Toꢀ theꢀ bestꢀofꢀ ourꢀ
knowledge,ꢀtheꢀsynthesisꢀofꢀCuOꢀNPsꢀusingꢀSCꢀmethodꢀhasꢀnotꢀ
beenꢀextensivelyꢀreportedꢀ[15].ꢀ
Inꢀtheꢀpresentꢀstudy,ꢀweꢀfocusꢀonꢀtheꢀsynthesisꢀofꢀCuOꢀNPsꢀ
viaꢀ anꢀ SCꢀ routeꢀ usingꢀ malicꢀ acidꢀ asꢀ aꢀ fuel.ꢀ Theꢀ combus‐
tion‐derivedꢀ CuOꢀ NPsꢀ possessꢀ aꢀ highꢀ surfaceꢀ areaꢀ withꢀ highꢀ
porosity.ꢀAꢀlargeꢀsurfaceꢀareaꢀresultsꢀinꢀtheꢀpotentialꢀforꢀmoreꢀ
activeꢀsitesꢀsuchꢀasꢀlow‐coordinateꢀoxideꢀsitesꢀ(edgesꢀandꢀcor‐
ners)ꢀandꢀlatticeꢀdefectsꢀ(anionsꢀandꢀcations)ꢀ[16].ꢀTheꢀporousꢀ
structureꢀalsoꢀfacilitatesꢀtheꢀadsorptionꢀandꢀdiffusionꢀofꢀreac‐
tantꢀ molecules.ꢀ Bothꢀ theꢀhighꢀsurfaceꢀareaꢀandꢀhighꢀporosityꢀ
enhanceꢀ theꢀ catalyticꢀ performance.ꢀ Althoughꢀ homogeneousꢀ
organicꢀbasicꢀcatalystsꢀareꢀdesirableꢀbecauseꢀofꢀtheirꢀhighꢀactiv‐
ityꢀ andꢀ selectivity,ꢀ theꢀ separationꢀ ofꢀ suchꢀ catalystsꢀ fromꢀ theꢀ
productsꢀofꢀtheꢀreactionꢀand/orꢀcatalystꢀrecoveryꢀareꢀinherentꢀ
problems.ꢀ ꢀ
Useꢀofꢀheterogeneousꢀbasicꢀcatalystsꢀhasꢀadvantagesꢀrelatedꢀ
toꢀeasyꢀseparation,ꢀefficientꢀrecycling,ꢀandꢀonlyꢀminimumꢀtracesꢀ
ofꢀ metalꢀ oxideꢀ remainingꢀ inꢀ theꢀ product.ꢀ Thisꢀ isꢀ particularlyꢀ
beneficialꢀtoꢀindustrialꢀprocessesꢀinꢀtheꢀdomainꢀofꢀgreenꢀchem‐
istry.ꢀThus,ꢀheterogeneousꢀbasicꢀcatalystsꢀhaveꢀbeenꢀrecognizedꢀ
asꢀpotentialꢀalternativesꢀtoꢀtheꢀmoreꢀcommonlyꢀusedꢀhomoge‐
neousꢀcatalysts.ꢀ
Theꢀsynthesisꢀofꢀnitrilesꢀfromꢀaldehydesꢀisꢀoneꢀofꢀtheꢀmostꢀ
importantꢀreactionsꢀinꢀorganicꢀchemistry.ꢀTheꢀnitrileꢀgroupꢀisꢀaꢀ
usefulꢀfunctionalꢀgroupꢀandꢀisꢀanꢀimportantꢀkeyꢀintermediateꢀinꢀ
organicꢀ synthesisꢀ [17].ꢀ Furthermore,ꢀ nitrileꢀ functionalityꢀ fre‐
quentlyꢀappearsꢀinꢀpharmaceuticalꢀproducts.ꢀForꢀexample,ꢀtheꢀ
cyanoꢀ groupꢀ isꢀ presentꢀ inꢀ HIVꢀ proteaseꢀ inhibitors,ꢀ
syntheticꢀorganicꢀchemistryꢀbecauseꢀofꢀtheirꢀrapidꢀreactionꢀrateꢀ
andꢀ easeꢀ ofꢀ manipulationꢀ [54].ꢀ Simpleꢀ experimentalꢀ proce‐
dures,ꢀhighꢀyields,ꢀimprovedꢀselectivity,ꢀandꢀcleanerꢀreactionsꢀ
ofꢀ manyꢀ microwave‐inducedꢀ organicꢀ transformationsꢀ offerꢀ
additionalꢀadvantages.ꢀOurꢀongoingꢀresearchꢀprogramꢀisꢀaimedꢀ
atꢀdevelopingꢀenvironmentallyꢀbenignꢀsyntheticꢀmethodologiesꢀ
suitableꢀ forꢀ organicꢀ compoundsꢀthatꢀareꢀwidelyꢀ usedꢀ [55,56].ꢀ
Weꢀwereꢀthereforeꢀinspiredꢀtoꢀattemptꢀtheꢀmicrowave‐assistedꢀ
synthesisꢀofꢀaromaticꢀnitrilesꢀfromꢀaromaticꢀaldehydesꢀunderꢀ
solvent‐freeꢀconditionsꢀusingꢀcatalyticꢀamountsꢀofꢀcopperꢀoxideꢀ
NPs.ꢀTheꢀcatalyticꢀactivityꢀofꢀbulkꢀCuOꢀinꢀcomparisonꢀwithꢀtheꢀ
combustion‐derivedꢀCuOꢀNPsꢀwasꢀalsoꢀevaluated.ꢀ ꢀ
2.ꢀ ꢀ Experimentalꢀ ꢀ
2.1.ꢀ ꢀ Materialsꢀ ꢀ
Copper(II)ꢀ nitrateꢀ trihydrateꢀ (98.8%ꢀ purity)ꢀandꢀ DL‐malicꢀ
acidꢀ(99%ꢀpurity)ꢀwereꢀpurchasedꢀfromꢀMerckꢀChemicalsꢀ(In‐
dia)ꢀ Pvt.ꢀ Ltd.ꢀ Allꢀ organicꢀ chemicalsꢀ usedꢀ wereꢀ ofꢀ commercialꢀ
gradeꢀandꢀprocuredꢀfromꢀMerckꢀChemicalsꢀ(India)ꢀPvt.ꢀLtd.ꢀAllꢀ
solidꢀaldehydesꢀwereꢀusedꢀwithoutꢀfurtherꢀpurification;ꢀliquidꢀ
aldehydesꢀwereꢀdistilledꢀbeforeꢀuse.ꢀ ꢀ
2.2.ꢀ ꢀ SynthesisꢀofꢀCuOꢀnanoparticlesꢀ
Anꢀaqueousꢀsolutionꢀcontainingꢀaꢀmixtureꢀofꢀcopper(II)ꢀni‐
trateꢀ asꢀ anꢀ oxidizerꢀ (O)ꢀ andꢀ malicꢀ acidꢀ asꢀ aꢀ fuelꢀ (F)ꢀ (corre‐
spondingꢀ F/Oꢀ ratioꢀ =ꢀ 1:1)ꢀ wasꢀ placedꢀ inꢀ aꢀ petriꢀdishꢀ[57,58].ꢀ
Excessꢀ waterꢀ wasꢀ allowedꢀ toꢀ evaporateꢀ byꢀ heatingꢀ onꢀ aꢀ hotꢀ
plateꢀuntilꢀitꢀdecomposedꢀwithꢀfrothingꢀasꢀaꢀresultꢀofꢀformationꢀ
ofꢀviscousꢀgel.ꢀTheꢀpetriꢀdishꢀwasꢀthenꢀplacedꢀinꢀaꢀmuffleꢀfur‐
naceꢀmaintainedꢀatꢀ(450ꢀ±ꢀ10)ꢀ°C.ꢀInitially,ꢀtheꢀviscousꢀgelꢀun‐
derwentꢀdehydrationꢀandꢀcommencedꢀsmolderingꢀcombustion,ꢀ
whichꢀappearedꢀatꢀoneꢀendꢀandꢀpropagatedꢀthroughꢀtheꢀmassꢀ
withinꢀ 1ꢀ min.ꢀ Voluminousꢀ andꢀ porousꢀ nanocrystallineꢀ
black‐coloredꢀ productꢀ wasꢀ obtained.ꢀ Thisꢀ non‐carbonaceousꢀ
powderꢀisꢀhereafterꢀreferredꢀtoꢀasꢀCuOꢀNPs.ꢀ ꢀ
5‐lipoxygenaseꢀ inhibitors,ꢀ andꢀ inꢀ manyꢀ otherꢀ bioactiveꢀ mole‐
culesꢀ [18,19].ꢀ Nitrilesꢀ alsoꢀ serveꢀ asꢀ usefulꢀ precursorsꢀ inꢀ theꢀ
synthesisꢀ ofꢀ carboxylicꢀ acidsꢀ [20,21],ꢀ ketenesꢀ [22],ꢀ aminesꢀ
[23,24],ꢀamidesꢀ[25],ꢀandꢀheterocyclicꢀcompoundsꢀ[26].ꢀ ꢀ
Overꢀtheꢀyears,ꢀmethodsꢀhaveꢀbeenꢀdevelopedꢀforꢀtheꢀsyn‐
thesisꢀ ofꢀ nitriles,ꢀ includingꢀ theꢀ nucleophilicꢀ displacementꢀ ofꢀ
groupsꢀ suchꢀ asꢀ halogens,ꢀ arylꢀ sulfonates,ꢀ alcohols,ꢀ esters,ꢀ
ethers,ꢀandꢀofꢀnitro,ꢀamino,ꢀandꢀdiazoniumꢀgroupsꢀinꢀsubstratesꢀ
withꢀ inorganicꢀ cyanideꢀ ionsꢀ [27,28].ꢀ Alternativeꢀ methodsꢀ forꢀ
theꢀsynthesisꢀofꢀnitrilesꢀinvolveꢀdehydrationꢀofꢀamidesꢀ[29,30]ꢀ
andꢀ aldoximesꢀ [31–33].ꢀ Conversionꢀ ofꢀ aldehydesꢀ [34–41],ꢀ al‐
coholsꢀ[42–44],ꢀandꢀcarboxylicꢀacidsꢀ[45–48]ꢀtoꢀnitrilesꢀusingꢀ
variousꢀreagentsꢀandꢀtheꢀdirectꢀconversionꢀofꢀaminesꢀ[49–52]ꢀ
areꢀalsoꢀdocumentedꢀinꢀtheꢀliterature.ꢀHowever,ꢀtheseꢀmethodsꢀ
ofꢀ synthesizingꢀ nitrilesꢀ sufferꢀ fromꢀ limitationsꢀ suchꢀ asꢀ pro‐
longedꢀreactionꢀtime,ꢀlowꢀyield,ꢀtheꢀnecessaryꢀuseꢀofꢀtoxicꢀrea‐
gentsꢀ andꢀ solvents,ꢀ aꢀ requirementꢀ forꢀ excessꢀ rea‐
gents/catalysts,ꢀlaboriousꢀwork‐upꢀprocedures,ꢀorꢀharshꢀreac‐
tionꢀconditions.ꢀThus,ꢀtheꢀdevelopmentꢀofꢀanꢀalternate,ꢀmilder,ꢀ
andꢀcleanerꢀprocedureꢀisꢀhighlyꢀdesirable.ꢀ
2.3.ꢀ ꢀ Generalꢀprocedureꢀ
Aꢀmixtureꢀofꢀaldehydeꢀ(2ꢀmmol),ꢀhydroxylamineꢀhydrochlo‐
rideꢀ(3ꢀmmol),ꢀandꢀcopperꢀoxideꢀNPsꢀ(5ꢀmol%)ꢀwasꢀplacedꢀinꢀaꢀ
Pyrexꢀcylindricalꢀtubeꢀandꢀthenꢀhomogenizedꢀandꢀirradiatedꢀatꢀ
250ꢀ Wꢀ inꢀ aꢀ MILESTONEꢀ microwaveꢀ reactor.ꢀ Afterꢀ irradiationꢀ
(1–2ꢀmin),ꢀtheꢀmixtureꢀwasꢀcooledꢀtoꢀ25ꢀ°Cꢀandꢀextractedꢀwithꢀ
dichloromethaneꢀ (5ꢀ mlꢀ×ꢀ2).ꢀ Theꢀ solventꢀ wasꢀ filteredꢀ underꢀ
vacuumꢀandꢀtheꢀorganicꢀlayerꢀ driedꢀoverꢀ fusedꢀcalciumꢀchlo‐
ride.ꢀ Theꢀ crudeꢀ productꢀ wasꢀ thenꢀ subjectedꢀ toꢀ short‐columnꢀ
silicaꢀ gelꢀ chromatographyꢀ usingꢀ lightꢀ petrolꢀ asꢀ anꢀ eluentꢀ toꢀ
produceꢀpureꢀproduct.ꢀ ꢀ
NMRꢀspectraꢀofꢀtheꢀorganicꢀcompoundsꢀwereꢀobtainedꢀonꢀaꢀ
400ꢀMHzꢀBrukerꢀAMXꢀspectrometerꢀinꢀDMSO‐d6ꢀusingꢀTMSꢀasꢀ
aꢀ standard.ꢀ Gasꢀchromatography‐massꢀ spectroscopyꢀ(GC‐MS)ꢀ
patternsꢀ wereꢀ obtainedꢀ usingꢀ aꢀ Shimadzuꢀ GC‐MSꢀ QPꢀ 5050Aꢀ
instrumentꢀequippedꢀwithꢀaꢀ30‐mꢀlongꢀandꢀ0.32‐mmꢀdiameterꢀ
BP‐5ꢀ columnꢀ atꢀtemperaturesꢀfromꢀ80ꢀtoꢀ250ꢀ°Cꢀwithꢀanꢀinter‐
Organicꢀ synthesesꢀ involvingꢀ greenerꢀ processesꢀ underꢀ sol‐
vent‐freeꢀconditionsꢀhaveꢀbeenꢀinvestigatedꢀasꢀaꢀconsequenceꢀ
ofꢀ stringentꢀ environmentalꢀ andꢀ economicꢀ regulationsꢀ [53].ꢀ Inꢀ
thisꢀ context,ꢀ microwave‐assistedꢀ reactionsꢀ areꢀ significantꢀ forꢀ

ꢀ
BelladamaduꢀSiddappaꢀANANDAKUMARꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ704–710ꢀ
valꢀ ofꢀ 15ꢀ °C.ꢀ IRꢀ spectraꢀ wereꢀ recordedꢀ usingꢀ aꢀ Shimadzuꢀ
FT‐IR‐8400sꢀspectrometerꢀwithꢀKBrꢀpelletsꢀusedꢀforꢀsolidsꢀandꢀ
withꢀthinꢀfilmsꢀbetweenꢀNaClꢀplatesꢀinꢀtheꢀcaseꢀofꢀliquids.ꢀ
(a)
2.4.ꢀ ꢀ Characterizationꢀofꢀcatalystsꢀ
PowderꢀX‐rayꢀdiffractionꢀ(PXRD)ꢀdataꢀ wereꢀrecordedꢀonꢀ aꢀ
PhilipsꢀX’pertꢀPROꢀX‐rayꢀdiffractometerꢀusingꢀgraphiteꢀmono‐
chromatizedꢀCuꢀK ꢀradiationꢀ(λꢀ=ꢀ0.1541ꢀnm)ꢀoperatedꢀatꢀ40ꢀkVꢀ
α
andꢀ30ꢀmA.ꢀTheꢀmorphologiesꢀofꢀtheꢀproductsꢀwereꢀexaminedꢀ
usingꢀ aꢀ Quanta‐200ꢀ scanningꢀ electronꢀ microscopeꢀ equippedꢀ
withꢀ anꢀ energy‐dispersiveꢀ X‐rayꢀ spectroscope.ꢀ Samplesꢀ wereꢀ
gold‐coatedꢀpriorꢀtoꢀscanningꢀelectronꢀmicroscopyꢀ(SEM)ꢀanal‐
ysis.ꢀTheꢀnano/microstructureꢀofꢀtheꢀproductsꢀwasꢀobservedꢀbyꢀ
transmissionꢀ electronꢀ microscopyꢀ (TEM)ꢀ andꢀ selected‐areaꢀ
electronꢀdiffractionꢀ(SAED),ꢀwhichꢀwasꢀperformedꢀusingꢀaꢀHi‐
tachiꢀ modelꢀ H‐600ꢀ instrumentꢀ operatingꢀ atꢀ 100ꢀ kV.ꢀ Surfaceꢀ
areaꢀ measurementsꢀ andꢀ poreꢀ sizeꢀ distributionꢀ analysesꢀ wereꢀ
carriedꢀoutꢀ afterꢀ degassingꢀ theꢀ sampleꢀ underꢀ highꢀ vacuumꢀ atꢀ
(
b)
ꢀ
3
00ꢀ°Cꢀ forꢀ 4ꢀ h,ꢀ andꢀ nitrogenꢀ adsorptionꢀ measurementsꢀ wereꢀ
carriedꢀ outꢀ atꢀ –196ꢀ °Cꢀ usingꢀ gasꢀ sorptionꢀ analyzerꢀ
QuantachromeꢀCorporationꢀNOVAꢀ1000).ꢀ ꢀ
Fig.ꢀ 2.ꢀ ꢀ SEMꢀimageꢀofꢀbulkꢀCuOꢀpowderꢀ(a)ꢀandꢀtheꢀCuOꢀnanoparticlesꢀ
b).ꢀ
(
(
theꢀamountꢀofꢀgasesꢀthatꢀescapedꢀduringꢀcombustion.ꢀTheꢀpro‐
cessꢀofꢀagglomerationꢀtakesꢀplaceꢀbecauseꢀofꢀanꢀincreaseꢀinꢀtheꢀ
rateꢀofꢀnucleationꢀofꢀtheꢀparticlesꢀatꢀhigherꢀtemperatures.ꢀ ꢀ
Theꢀ elementalꢀ quantificationꢀ andꢀ stoichiometricꢀ ratioꢀ ofꢀ
copperꢀoxideꢀNPsꢀwereꢀconfirmedꢀbyꢀenergy‐dispersiveꢀX‐rayꢀ
analysisꢀ(EDX),ꢀwhichꢀshowedꢀtheꢀpresenceꢀofꢀaꢀuniformꢀdis‐
tributionꢀofꢀcopperꢀtoꢀoxygenꢀ(atomicꢀratioꢀofꢀ1:1)ꢀinꢀCuOꢀNPs,ꢀ
asꢀshownꢀinꢀFig.ꢀ3.ꢀThisꢀagreesꢀwellꢀwithꢀtheꢀresultsꢀobtainedꢀ
viaꢀXRD.ꢀ
TheꢀTEMꢀimageꢀinꢀFig.ꢀ4(a)ꢀshowsꢀaꢀnetworkꢀofꢀlargerꢀparti‐
clesꢀthatꢀareꢀofꢀmoderateꢀsizeꢀandꢀthatꢀareꢀirregularlyꢀshaped,ꢀ
formedꢀbyꢀtheꢀagglomerationꢀofꢀwell‐dispersedꢀNPsꢀwithꢀaver‐
ageꢀ sizesꢀ ofꢀ 20–30ꢀ nm.ꢀ Theꢀ sizesꢀ ofꢀ theseꢀ NPsꢀ areꢀ inꢀ goodꢀ
agreementꢀ withꢀ theꢀ valuesꢀ obtainedꢀ fromꢀ XRDꢀ analysis.ꢀ Theꢀ
phaseꢀ purity,ꢀ clearꢀ morphology,ꢀ andꢀ crystallinityꢀ wereꢀ con‐
firmedꢀbyꢀSAED.ꢀSAEDꢀ(inset)ꢀprovidesꢀsupportingꢀevidenceꢀforꢀ
theꢀpolycrystallineꢀstructureꢀofꢀtheꢀCuOꢀNPs.ꢀ ꢀ
3
.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
3.1.ꢀ ꢀ Catalystꢀcharacterizationꢀresultsꢀ
Figureꢀ1ꢀshowsꢀtheꢀXRDꢀpatternꢀrecordedꢀforꢀtheꢀCuOꢀNPs,ꢀ
whereꢀ allꢀ diffractionꢀ peaksꢀ haveꢀ beenꢀ indexedꢀ toꢀ theꢀ pureꢀ
monoclinicꢀ crystallineꢀ phaseꢀ ofꢀ CuO.ꢀ Theseꢀ valuesꢀ areꢀ con‐
sistentꢀ withꢀ thoseꢀ reportedꢀ inꢀ theꢀ literatureꢀ andꢀ withꢀ theꢀ re‐
spectiveꢀJCPDSꢀcardꢀNo.ꢀ45‐0937.ꢀTheꢀbroadnessꢀofꢀtheꢀpeaksꢀ
indicatesꢀ theꢀ nanocrystallineꢀ natureꢀ ofꢀ theꢀ CuOꢀ NPsꢀ andꢀ theꢀ
particleꢀ sizeꢀ calculatedꢀ fromꢀ theꢀ Scherrer’sꢀ formulaꢀ (Dꢀ =ꢀ
Κλ/βcosθ)ꢀisꢀinꢀtheꢀrangeꢀofꢀ20–30ꢀnm.ꢀ
Theꢀmorphologiesꢀ ofꢀ theꢀ bulkꢀ CuOꢀ powderꢀ andꢀ combus‐
tion‐derivedꢀCuOꢀnanopowderꢀwereꢀinvestigatedꢀbyꢀSEM.ꢀTheꢀ
SEMꢀ imageꢀ ofꢀ bulkꢀ CuOꢀ powderꢀ (Fig.ꢀ 2(a))ꢀ revealsꢀ thatꢀ theꢀ
powderꢀ hasꢀ lessꢀ porosityꢀ comparedꢀ withꢀ theꢀ combus‐
tion‐derivedꢀCuOꢀnanopowder.ꢀTheꢀSEMꢀmicrographꢀ(Fig.ꢀ2(b))ꢀ
revealsꢀthatꢀtheꢀlatterꢀpowderꢀisꢀporousꢀandꢀagglomeratedꢀwithꢀ
polycrystallineꢀNPs.ꢀTheꢀporesꢀandꢀvoidsꢀcanꢀbeꢀattributedꢀtoꢀ
Theꢀ surfaceꢀ areaꢀ ofꢀ theꢀ CuOꢀ NPsꢀ wasꢀ measuredꢀ usingꢀ theꢀ
2
BETꢀmethod.ꢀTheꢀCuOꢀNPsꢀhaveꢀaꢀlargerꢀsurfaceꢀareaꢀ(52ꢀm /g)ꢀ
2
comparedꢀ withꢀ thatꢀ ofꢀ bulkꢀ CuOꢀ (10–12ꢀ m /g).ꢀ Thisꢀcanꢀbeꢀ
attributedꢀ toꢀ theꢀ liberationꢀ ofꢀ gaseousꢀ productsꢀ suchꢀ asꢀ H O,ꢀ
2
Cu
Cu
O
30
40
50
/( )
60
70
0
4
8
12
16
o
2
Energy (keV)
Fig.ꢀ1.ꢀ ꢀ XRDꢀpatternꢀofꢀtheꢀCuOꢀnanoparticlesꢀsynthesizedꢀinꢀthisꢀwork.
Fig.ꢀ3.ꢀ ꢀ EDXꢀspectrumꢀofꢀtheꢀCuOꢀNPs.ꢀ

ꢀ
BelladamaduꢀSiddappaꢀANANDAKUMARꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ704–710ꢀ
ꢀ
indicatesꢀtheꢀformationꢀofꢀdualꢀmesopores,ꢀwithꢀtheꢀpeakꢀatꢀ45ꢀ
nmꢀdueꢀtoꢀtheꢀmesoporeꢀopeningꢀleadingꢀintoꢀtheꢀmainꢀcavityꢀ
andꢀaꢀlargeꢀnumberꢀofꢀmesoporesꢀuniformlyꢀdistributedꢀinꢀtheꢀ
CuOꢀNPsꢀatꢀ48ꢀnm.ꢀTheꢀporeꢀsizeꢀdistribution,ꢀwithꢀreferenceꢀtoꢀ
theꢀaverageꢀporeꢀdiameterꢀrangeꢀandꢀporeꢀvolumeꢀrangeꢀcalcu‐
latedꢀviaꢀtheꢀBarrett‐Joyner‐Halendaꢀmethod,ꢀwereꢀfoundꢀtoꢀbeꢀ
3
4
4.82–48.36ꢀ nmꢀ andꢀ 0.431–0.441ꢀ cm /g,ꢀ respectively.ꢀ Theseꢀ
valuesꢀ areꢀ inꢀ goodꢀ agreementꢀ withꢀ theꢀ valuesꢀ obtainedꢀ fromꢀ
theꢀporeꢀsizeꢀdistributionꢀplotꢀ(Fig.ꢀ5).ꢀ
3.2.ꢀ ꢀ Catalyticꢀactivityꢀ
Inꢀtheꢀ courseꢀofꢀtheꢀ reactionꢀitꢀwasꢀfoundꢀ that,ꢀunderꢀmi‐
crowaveꢀ heating,ꢀ theꢀ reactionꢀ ofꢀ anꢀ araldehydeꢀ withꢀ hydrox‐
ylamineꢀ hydrochlorideꢀ inꢀ theꢀ presenceꢀ ofꢀ CuOꢀ NPsꢀ isꢀ rapid,ꢀ
clean,ꢀ andꢀ highꢀyielding.ꢀ Toꢀ optimizeꢀ theꢀ reactionꢀ conditions,ꢀ
weꢀstudiedꢀtheꢀreactionꢀofꢀ4‐methoxybenzaldehydeꢀ(2ꢀmmol)ꢀ
withꢀhydroxylamineꢀhydrochlorideꢀ(3ꢀmmol)ꢀinꢀtheꢀpresenceꢀofꢀ
CuOꢀNPsꢀ(5ꢀmol%)ꢀunderꢀmicrowaveꢀirradiation.ꢀTheꢀstartingꢀ
materialꢀ completelyꢀ reactedꢀ withinꢀ60ꢀ s,ꢀasꢀindicatedꢀ byꢀ TLCꢀ
analysis.ꢀ Afterꢀ isolationꢀ andꢀ purificationꢀ byꢀ silicaꢀ gelꢀ columnꢀ
chromatography,ꢀ 4‐methoxybenzonitrileꢀ wasꢀ isolatedꢀ withꢀ aꢀ
98%ꢀyield.ꢀ ꢀ
Theꢀeffectꢀofꢀcatalystꢀloadꢀonꢀtheꢀreactionꢀtimeꢀandꢀyieldꢀwasꢀ
studied.ꢀTheꢀbestꢀresultꢀwasꢀobtainedꢀwithꢀ5ꢀmol%ꢀofꢀtheꢀcata‐
lystꢀ whichꢀ gaveꢀ 98%ꢀ yieldꢀ withinꢀ 60ꢀ s.ꢀ Theꢀ useꢀ ofꢀ aꢀ lesserꢀ
amountꢀofꢀcatalystꢀ(<ꢀ5ꢀmol%)ꢀresultedꢀinꢀlowerꢀyields,ꢀbutꢀaꢀ
higherꢀamountꢀofꢀcatalystꢀ(>ꢀ5ꢀmol%)ꢀdidꢀnotꢀaffectꢀtheꢀreactionꢀ
withꢀ respectꢀ toꢀ eitherꢀ durationꢀ orꢀ yield.ꢀ However,ꢀ inꢀ theꢀ ab‐
senceꢀofꢀtheꢀcatalyst,ꢀtheꢀyieldꢀofꢀtheꢀnitrileꢀwasꢀlowꢀ(<ꢀ5%)ꢀandꢀ
oximeꢀwasꢀaꢀmajorꢀproductꢀ(>ꢀ90%)ꢀafterꢀ2ꢀminꢀofꢀirradiationꢀ
atꢀ 250ꢀ W.ꢀ Choosingꢀ anꢀ appropriateꢀ solventꢀ isꢀ ofꢀ criticalꢀ im‐
portanceꢀ forꢀ successfulꢀ microwave‐assistedꢀ synthesis.ꢀ Toꢀ
searchꢀ forꢀ theꢀ optimalꢀ solvent,ꢀ theꢀ reactionꢀ ofꢀ
4‐methoxybenzaldehydeꢀ (2ꢀmmol),ꢀ hydroxylamineꢀ hydrochlo‐
rideꢀ (3ꢀmmol),ꢀ andꢀ CuOꢀ NPsꢀ (5ꢀ mol%)ꢀ wasꢀ examinedꢀ usingꢀ
water,ꢀ methanol,ꢀ ethanol,ꢀ MeCN,ꢀ DMF,ꢀ THF,ꢀ ethylꢀ acetate,ꢀ di‐
ethylꢀether,ꢀandꢀhexaneꢀasꢀsolvents,ꢀatꢀ100ꢀ°Cꢀunderꢀmicrowaveꢀ
irradiationꢀconditions.ꢀAllꢀofꢀtheꢀreactionsꢀwereꢀcarriedꢀoutꢀatꢀ
theꢀ maximumꢀ powerꢀ ofꢀ 250ꢀ W.ꢀ Theꢀ yieldsꢀ ofꢀ theꢀ nitrileꢀ asꢀ aꢀ
minorꢀproductꢀwereꢀ0,ꢀ5%,ꢀ3%,ꢀ8%,ꢀ7%,ꢀ6%,ꢀ4%,ꢀ8%,ꢀandꢀ5%ꢀ
forꢀtheꢀrespectiveꢀsolventsꢀlistedꢀabove,ꢀandꢀoximeꢀasꢀaꢀmajorꢀ
productꢀwasꢀproducedꢀinꢀyieldsꢀofꢀ65%,ꢀ70%,ꢀ73%,ꢀ78%,ꢀ69%,ꢀ
ꢀ
Fig.ꢀ 4.ꢀ ꢀ TEMꢀimageꢀofꢀtheꢀCuOꢀnanoparticlesꢀandꢀSAEDꢀpatternꢀofꢀCuO
inset).ꢀ
(
CO
2
,ꢀ andꢀ N ꢀ duringꢀ combustion,ꢀ wherebyꢀ theꢀ agglomeratesꢀ
2
disintegrateꢀandꢀmostꢀofꢀtheꢀheatꢀisꢀcarriedꢀawayꢀfromꢀtheꢀsys‐
tem,ꢀthusꢀhinderingꢀparticleꢀgrowth.ꢀThisꢀlargerꢀsurfaceꢀareaꢀisꢀ
importantꢀ forꢀ catalytic/adsorbentꢀ applicationsꢀ becauseꢀ theꢀ
smallꢀ sizeꢀ ofꢀ theꢀ particlesꢀ maximizesꢀ theꢀ surfaceꢀ areaꢀ thatꢀ isꢀ
exposedꢀtoꢀtheꢀreactant,ꢀallowingꢀmoreꢀreactionsꢀtoꢀoccur.ꢀFig‐
ureꢀ5ꢀshowsꢀaꢀrepresentativeꢀadsorption‐desorptionꢀisothermꢀ
ofꢀnitrogenꢀobtainedꢀatꢀtheꢀtemperatureꢀofꢀliquidꢀnitrogen.ꢀThis,ꢀ
accordingꢀtoꢀtheꢀIUPACꢀclassification,ꢀisꢀaꢀtypeꢀIVꢀisothermꢀwithꢀ
typeꢀ H1ꢀ hysteresis.ꢀ Typeꢀ H1ꢀ hysteresisꢀ indicatesꢀ that,ꢀ forꢀ
sphericalꢀpores,ꢀtheꢀporeꢀopeningꢀisꢀsmallerꢀthanꢀtheꢀdiameterꢀ
ofꢀtheꢀmainꢀcavity.ꢀAsꢀtheꢀdesorptionꢀportionꢀofꢀtheꢀisothermꢀ
movesꢀfromꢀhigherꢀpartialꢀpressureꢀtoꢀlowerꢀpartialꢀpressure,ꢀaꢀ
gradualꢀdecreaseꢀinꢀporeꢀvolumeꢀisꢀobserved.ꢀAsꢀwithꢀtheꢀad‐
sorptionꢀ portionꢀ ofꢀ theꢀ isotherm,ꢀ thisꢀ isꢀ anꢀ indicationꢀ ofꢀ theꢀ
broadꢀdistributionꢀofꢀmesoporesꢀinꢀtheꢀCuOꢀNPs.ꢀTheꢀtypeꢀIVꢀ
isothermꢀsuggestsꢀtheꢀpresenceꢀofꢀmesoporesꢀinꢀtheꢀCuOꢀNPsꢀ
andꢀthisꢀwasꢀconfirmedꢀbyꢀtheꢀresultsꢀofꢀporeꢀsizeꢀdistributionꢀ
measurements.ꢀTheꢀporeꢀsizeꢀdistributionꢀprofileꢀexhibitsꢀtwoꢀ
peaksꢀforꢀtheꢀCuOꢀNPsꢀcenteredꢀatꢀ45ꢀandꢀ48ꢀnm.ꢀThisꢀresultꢀ
3
2
2
1
1
00
50
00
50
00
0.004
0.003
74%,ꢀ 66%,ꢀ 71%,ꢀ andꢀ 77%,ꢀ respectively.ꢀ Contrastingly,ꢀ for‐
0.002
0.001
0.000
mationꢀofꢀtheꢀcorrespondingꢀnitrileꢀ(93%)ꢀasꢀaꢀmajorꢀproductꢀ
wasꢀobservedꢀwhenꢀtheꢀsameꢀreactionꢀwasꢀcarriedꢀoutꢀunderꢀ
solvent‐freeꢀ conditions.ꢀ Thisꢀ studyꢀ clearlyꢀ showsꢀ thatꢀ micro‐
waveꢀirradiationꢀinꢀ conjunctionꢀ withꢀ CuOꢀ NPsꢀ (5ꢀ mol%)ꢀ asꢀ aꢀ
catalystꢀresultsꢀinꢀhighꢀyieldsꢀofꢀnitrilesꢀunderꢀsolvent‐freeꢀcon‐
ditions.ꢀTherefore,ꢀnoꢀsolventꢀwasꢀusedꢀforꢀtheꢀremainingꢀmi‐
crowave‐assistedꢀreactionsꢀtoꢀbeꢀdiscussedꢀbecauseꢀitꢀisꢀenvi‐
ronmentallyꢀfriendlyꢀandꢀtheꢀuseꢀofꢀtoxicꢀorganicꢀreagentsꢀcanꢀ
beꢀavoided.ꢀ
0
40 80 120 160 200
Pore diameter (nm)
5
0
0
0
.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (p/p
0
)
Weꢀ haveꢀ comparedꢀ theꢀ catalyticꢀactivityꢀ ofꢀ CuOꢀ NPsꢀ withꢀ
thatꢀofꢀbulkꢀcopperꢀoxide.ꢀWhenꢀtheꢀmodelꢀreactionsꢀbetweenꢀ
Fig.ꢀ 5.ꢀ ꢀ Nitrogenꢀadsorption‐desorptionꢀisothermꢀofꢀtheꢀCuOꢀnanopar‐
ticlesꢀ andꢀ poreꢀ sizeꢀ distributionꢀ curveꢀ (inset)ꢀ determinedꢀ fromꢀ the
4‐methoxybenzaldehydeꢀ (2ꢀmmol)ꢀandꢀ hydroxylamineꢀ hydro‐
2
N ‐desorptionꢀisotherm.ꢀ
chlorideꢀ(3ꢀmmol)ꢀwithꢀeitherꢀCuOꢀNPsꢀ(5ꢀmol%)ꢀorꢀbulkꢀCuOꢀ

ꢀ
BelladamaduꢀSiddappaꢀANANDAKUMARꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ704–710ꢀ
(
5ꢀ mol%)ꢀ wereꢀ conductedꢀ underꢀ theꢀ optimizedꢀ conditions,ꢀ
wereꢀ foundꢀ toꢀ giveꢀ theꢀ correspondingꢀ nitrilesꢀ withꢀ excellentꢀ
yieldꢀ(85%–98%).ꢀ
yieldsꢀofꢀ98%ꢀandꢀ39%,ꢀrespectively,ꢀwereꢀobtainedꢀafterꢀ60ꢀs.ꢀ
ThisꢀclearlyꢀindicatesꢀthatꢀCuOꢀNPsꢀenhanceꢀtheꢀcatalyticꢀactiv‐
ityꢀ inꢀ theꢀ synthesisꢀ ofꢀ aromaticꢀ nitrilesꢀ fromꢀ aromaticꢀ alde‐
hydes.ꢀ
Theꢀgeneralityꢀofꢀtheꢀaboveꢀreactionsꢀwasꢀtestedꢀbyꢀcarryingꢀ
outꢀtheꢀreactionsꢀwithꢀvariousꢀsubstitutedꢀaraldehydes.ꢀItꢀwasꢀ
consequentlyꢀfoundꢀthatꢀtheꢀreactionsꢀproceedꢀsmoothlyꢀirre‐
spectiveꢀ ofꢀ theꢀ substituentꢀ (seeꢀ Tableꢀ 1).ꢀ Araldehydesꢀ pos‐
sessingꢀ electronꢀ donatingꢀ groups,ꢀ e.g.,ꢀ –OMe,ꢀ –OHꢀ orꢀ –N,ꢀ
Weꢀfurtherꢀexploredꢀtheꢀeffectꢀofꢀincreasingꢀtheꢀpowerꢀandꢀ
reactionꢀtimeꢀinꢀtheꢀconversionꢀofꢀ4‐methoxybenzaldehydeꢀtoꢀ
4‐methoxybenzonitrile,ꢀ butꢀ noꢀ changeꢀ inꢀ productꢀ ratiosꢀ wasꢀ
observed.ꢀTheꢀidentityꢀofꢀtheꢀsynthesizedꢀcompoundsꢀwasꢀcon‐
firmedꢀbyꢀIRꢀanalysis.ꢀInꢀtheꢀIRꢀspectra,ꢀtheꢀcharacteristicꢀCNꢀ
stretchingꢀmodeꢀwasꢀobservedꢀatꢀ2220–2245ꢀcm−1
ꢀTheꢀmolec‐
.
+
ularꢀ ionꢀ peaksꢀ (M )ꢀ observedꢀ inꢀ theꢀ massꢀ spectraꢀ wereꢀ inꢀ
agreementꢀwithꢀtheꢀexpectedꢀmolecularꢀweights.ꢀTheꢀmeltingꢀ
orꢀ boilingꢀ pointsꢀ ofꢀ theꢀ compounds,ꢀ asꢀ givenꢀ inꢀ Tableꢀ 1,ꢀalsoꢀ
N(Me)
2
,ꢀelectronꢀwithdrawingꢀgroupsꢀsuchꢀasꢀ–NO ,ꢀorꢀhalidesꢀ
2
Tableꢀ1ꢀ ꢀ
Solvent‐freeꢀsynthesisꢀofꢀnitrilesꢀfromꢀaldehydesꢀunderꢀmicrowaveꢀirradiationꢀatꢀ250ꢀW.ꢀ
Isolatedꢀyieldꢀ(%)ꢀ
CuOꢀNPsꢀ BulkꢀCuOꢀ
95ꢀ 34ꢀ
ꢀ
m.p.ꢀorꢀb.p.*( C)ꢀ
Reportedꢀ
o
Entryꢀ
Aldehydeꢀ
Productꢀ
Timeꢀ(s)ꢀ
ꢀ 65ꢀ
ꢀ
ꢀ
Foundꢀ
185*ꢀ
O
CN
1ꢀ
190*ꢀ[59]ꢀ
H
ꢀ
ꢀ
O
CN
2
ꢀ
ꢀ 60ꢀ
ꢀ 45ꢀ
98ꢀ
97ꢀ
39ꢀ
35ꢀ
ꢀ
ꢀ
55−56ꢀ
ꢀ 60ꢀ
57−59ꢀ[37]ꢀ
H
H
MeO
MeO
ꢀ
MeO
MeO
ꢀ
ꢀ
ꢀ
O
CN
CN
3ꢀ
63ꢀ[60]ꢀ
OMe
OMe
ꢀ
OMe
OMe
O
MeO
MeO
4ꢀ
ꢀ 55ꢀ
96ꢀ
34ꢀ
ꢀ
ꢀ 90ꢀ
92−94ꢀ[60]ꢀ
MeO
MeO
H
H
ꢀ
O
5ꢀ
CN
CN
ꢀ 45ꢀ
ꢀ 70ꢀ
93ꢀ
98ꢀ
32ꢀ
38ꢀ
ꢀ
ꢀ
110ꢀ
ꢀ 83ꢀ
110ꢀ[59]ꢀ
83ꢀ[60]ꢀ
HO
HO
HO
HO
ꢀ
O
6ꢀ
H
OMe
OMe
ꢀ
O
7ꢀ
CN
ꢀ 85ꢀ
90ꢀ
30ꢀ
ꢀ
ꢀ 71ꢀ
73−75ꢀ[59]ꢀ
H
N
N
ꢀ
O
CN
8
ꢀ
ꢀ 80ꢀ
ꢀ 95ꢀ
94ꢀ
95ꢀ
33ꢀ
34ꢀ
ꢀ
ꢀ
ꢀ 92ꢀ
ꢀ 38ꢀ
94ꢀ[59]ꢀ
H
Cl
ꢀ
Cl
ꢀ
O
O
9ꢀ
CN
37−39ꢀ[59]ꢀ
H
Cl
Cl
ꢀ
ꢀ
1
0ꢀ
1ꢀ
CN
ꢀ 75ꢀ
ꢀ 90ꢀ
96ꢀ
92ꢀ
35ꢀ
32ꢀ
ꢀ
ꢀ
ꢀ 40ꢀ
112ꢀ
43−46ꢀ[59]ꢀ
115ꢀ[59]ꢀ
H
H
Cl
Cl
O
1
CN
NO2
NO2
ꢀ
ꢀ
O
12ꢀ
CN
100ꢀ
95ꢀ
33ꢀ
ꢀ
104−106ꢀ
107ꢀ[59]ꢀ
H
NO2
NO2
Otherꢀconditions:ꢀaldehydeꢀ2ꢀmmol,ꢀhydroxylamineꢀhydrochlorideꢀ3ꢀmmol,ꢀCuOꢀNPsꢀ5ꢀmol%.ꢀ ꢀ

ꢀ
BelladamaduꢀSiddappaꢀANANDAKUMARꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ704–710ꢀ
ꢀ
aldehydesꢀ andꢀ hydroxylamineꢀ hydrochlorideꢀ hasꢀ beenꢀ devel‐
no -NC au nOo -CuO
Nano-CuO
Nan No a- Cn ou -OC uO
oped.ꢀ Aꢀ wideꢀ rangeꢀ ofꢀ nitrilesꢀ haveꢀ beenꢀ synthesizedꢀ underꢀ
solvent‐freeꢀconditionsꢀinꢀaꢀshortꢀreactionꢀtime.ꢀThisꢀprotocolꢀ
couldꢀ proveꢀ toꢀ beꢀ aꢀ practicalꢀ alternativeꢀ forꢀ theꢀ synthesisꢀ ofꢀ
nitriles,ꢀespeciallyꢀinꢀdifficultꢀcasesꢀwhereinꢀlowꢀnucleophilicityꢀ
ofꢀtheꢀaldehydesꢀinhibitsꢀtheꢀreaction.ꢀTheꢀproposedꢀmethodꢀforꢀ
obtainingꢀ aromaticꢀ nitrilesꢀ isꢀ anꢀ inexpensive,ꢀ convenient,ꢀ andꢀ
environmentallyꢀ friendlyꢀ techniqueꢀthatꢀisꢀ suitableꢀ forꢀ indus‐
trialꢀproduction.ꢀ
H
OH
O
N
OH
N
O
O
N
-
_
H
2
O
H O
2
_
Ph
H
H
H
O
Ph Ph
H
-
H O
h
PhH
H
2
H
(
i) (i
(
)
i)
2
Ph
N
(iii)
.
.
. .
OH
(iii)
(iv)
NH O NH H OH
2
2
(ii)
(ii)
Schemeꢀ 1.ꢀ ꢀ Proposedꢀ mechanismꢀ forꢀ theꢀ catalyticꢀ synthesisꢀ ofꢀ aro‐
maticꢀnitrilesꢀfromꢀaromaticꢀaldehydes.ꢀ
agreeꢀwithꢀtheꢀliteratureꢀvalues.ꢀAsꢀcanꢀbeꢀseenꢀfromꢀTableꢀ1,ꢀ
CuOꢀNPsꢀcanꢀserveꢀasꢀanꢀefficientꢀcatalystꢀinꢀtheꢀformationꢀofꢀ
Acknowledgementsꢀ
4
‐methoxybenzonitrilesꢀ withꢀ highꢀ yieldsꢀ inꢀ shortꢀ reactionꢀ
G.T.C.ꢀ gratefullyꢀ acknowledgesꢀ theꢀ financialꢀ supportꢀ ofꢀ theꢀ
UniversityꢀGrantsꢀCommission,ꢀNewꢀDelhi.ꢀAuthorsꢀareꢀthankfulꢀ
toꢀProf.ꢀSaralaꢀUpadhya,ꢀDepartmentꢀofꢀMechanicalꢀEngineer‐
ing,ꢀUVCE,ꢀBangaloreꢀUniversity,ꢀforꢀrecordingꢀtheꢀSEMꢀimages.ꢀ
times.ꢀTheꢀsizeꢀofꢀtheꢀCuOꢀplaysꢀanꢀimportantꢀroleꢀinꢀtermsꢀofꢀ
yieldꢀandꢀreactionꢀtime.ꢀChangingꢀtheꢀsizeꢀofꢀtheꢀparticlesꢀfromꢀ
nanoparticlesꢀtoꢀbulkꢀresultedꢀinꢀaꢀdropꢀinꢀtheꢀcatalyticꢀactivityꢀ
(entryꢀ2ꢀofꢀTableꢀ1).ꢀItꢀisꢀinterestingꢀtoꢀnoteꢀthatꢀtheꢀCuOꢀnano‐
particlesꢀcatalyzeꢀtheꢀpresentꢀreactionꢀinꢀhighꢀyieldꢀandꢀwithinꢀ
aꢀshorterꢀreactionꢀtimeꢀcomparedꢀwithꢀtheꢀotherꢀcatalysts.ꢀ
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ꢀ
BelladamaduꢀSiddappaꢀANANDAKUMARꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ704–710ꢀ
GraphicalꢀAbstractꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2013,ꢀ34:ꢀ704–710ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(11)60503‐2ꢀ
Combustion‐derivedꢀCuOꢀnanoparticles:ꢀAnꢀeffectiveꢀandꢀenvironmentallyꢀbenignꢀcatalystꢀinꢀtheꢀsynthesisꢀofꢀaromaticꢀnitrilesꢀ
fromꢀaromaticꢀaldehydesꢀ
BelladamaduꢀSiddappaꢀANANDAKUMAR,ꢀMuthukurꢀBhojegowdꢀMadhusudanaꢀREDDY,ꢀChikkaꢀNagaiahꢀTHARAMANI,ꢀ ꢀ
ꢀ
MohamedꢀAfzalꢀPASHA,ꢀGujjarahalliꢀThimmannaꢀCHANDRAPPA*ꢀ
BangaloreꢀUniversity,ꢀIndia;ꢀRuhrꢀUniversitätꢀBochum,ꢀGermanyꢀ
CuOꢀnanoparticlesꢀshowꢀexcellentꢀcatalyticꢀactivityꢀinꢀtheꢀsynthesisꢀofꢀaromaticꢀnitrilesꢀfromꢀaromaticꢀaldehydes.ꢀTheꢀpresentꢀapproachꢀ
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