hydrolysis of nitriles to carboxylic acid：腈水解为羧酸

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1、CHE311LNorthernKentuckyUniversityHydrolysisofBenzonitrileRequiredPre-LabReadings:McMurrySections15.7&16.7.Techniquesyoumustbepreparedtoperform:Reflux(pp59-63)andRecrystallization(pp183-197).IntroductionNitrilesarederivativesofcarboxylicacidsand,asisthecaseofallderivatives

2、ofcarboxylicacids,theycanbehydrolyzed(literally,“tobreakwithwater”)tothecarboxylicacid.Inthecaseofnitrileseitheraddedacidorbaseandelevatedtemperaturesarerequired.Thehydrolysisofacidderivativesisofparticularimportanceinbiology.Thehydrolysisoffats(esters)andproteins(amides)

3、arejusttwoofmanyexamplesofhydrolysisreactionsthatoccurinanimals.Inthislabyouwillcompleteabasepromotedconversionofbenzonitriletobenzoicacid.Themechanisminvolvesinitialattackofthenucleophilichydroxideontheelectrophiliccarbon.Protontransferfromthesolvent(water)resultsinanint

4、ermediatethattautomerizestothecorrespondingamide.Theamideproceedsontothecarboxylatebyamechanismanalogoustothebasehydrolysisofesters.ProcedureIna50mLround-bottomflaskadd10mmolofbenzonitrile(____g;____mL),13mLofa10%solutionofNaOH(m/v;r=1.11g/mL)andastirbar.Addawater-cooledr

5、efluxcondenserandrefluxgentlyfor90minutes.Duringrefluxyoumaynoticeanodoratthetopofthecondenser(Whatcausesthisodor?).Afterrefluxingtheoilydropsofthestartingmaterialshouldhavemostlydisappeared.Removethemixturefromheat,chillthesolutioninanice/waterbathforseveralminutesandadd

6、cold6MHCl(withstirringasalways)untilthesolutionisacidicandprecipitationoftheproductiscomplete(ApproximatelyhowmuchHClsolutionwillyouneed?).Donotaddtheacidoneortwodropsatatime(thinkaboutwhatyoushouldsee).Collecttheproductbyvacuumfiltrationandwashwithcoldwater.Oncetheproduc

7、tisisolated,recrystallizethematerialfromwaterandallowtoairdryforaweekinthelabdrawer.Oncedriedrecordtheweightandmeltingpointofthebenzoicacidrecovered.Benzonitrile-4CHE311LNorthernKentuckyUniversityHydrolysisofBenzonitrileName:SectionNumber:OverallReaction:Volumeofbenzoniti

8、rle:Theommolbenzoicacid:mmolofbenzonitirle:Theomassbenzoicacid:VolumeofNaOH:Massrecoveredbenzoic