GeneralRecrystallizationProcedure-Home,Southeast：一般的再结晶过程-家居，东南

RevisedJune2009RecrystallizationofanImpureUnknownSolubilityPropertiesNeededforaRecrystallizationSolventThe__terialwearetryingtopurifymustbe:SolubleinthehotrecrystallizationsolventandInsolubleinthecoldrecrystallizationsolvent.TheImpuritiesmustbe:SolubleinbothhotandcoldrecrystallizationsolventorInsolubleinbothhotandcoldrecrystallizationsolvent.SafetyNote:Ifyouneedtoaddadditionalflam__blesolventtoaflaskorbeakeronthehotplateremovetheflaskorbeakerfromthehotplatefirstaddthesolventthenputtheflaskorbeakerbackontothehotplate.Thiswillminimizefiredanger.ChoosingaRecrystallizationSolvent:Trywater95%ethanoltolueneanda__tone.

1.Pla__about50mLofwaterina150mLbeakerandheatittoboilingonthehotplate.

2.Inamediumtest-tubeadda__allamountsizeofapencileraserofsolidand1-2mLofsolvent.

3.Ifitdissolvesincoldsolventitwon’tworksotryanothersolvent.

4.Ifitdoesn’tdissolveinthecoldsolventheatthetest-tubeup.Ifthesoliddissolvescoolitandseeifcrystalsform.Iftheydoit’sagoodsolvent.Ifnottryanothersolvent.

5.Ifnotallofthesoliddissolvesinthehotsolventaddmoresolventalittleatatimeandheatittoboiling.Donotfillthetest-tubemorethanhalf-full.Ifnotallofthe__terialdissolvesotherthaninsolubleimpuritiesinthehotsolventthesolventwon’twork.GeneralRecrystallizationPro__dure

1.Weighoutbetween1-2gramsofyourunknown.Recordexactlywhatyouuse.

2.Pla__yoursolidina125mLErle__eyerflask.Add10mLofyoursolvent.Heatthesolventtoboilingonthehotplate.

3.Ifnotallofthesampledissolvesadd5mLmoresolventandheattoboiling.Continuetodothisuntilallofthesamplehasdissolved.Watchoutforinsolubleimpurities!BestCase:ClearcolorlesssolutionA.Allowtheflasktocooltoclosetoroomtemperatureonthebenchtop.B.Coolyourflaskinani__-bath.HowlongUntilyourflaskiscold!C.Collectthesolidbysuctionfiltrationandwashitwithalittlecoldsolvent.D.Transferthecrystalstoawatchglassallowthemtodrythenweighthemandtakeameltingpoint.InsolubleImpuritiesOnlyA.Addabout50%additionalsolventandheattoboiling.B.Performahotgr__ityfiltrationonthehotplate.C.DoA-Dunder“BestCase”.ColoredSolutionWithorWithoutInsolubleImpuritiesA.Addabout50%additionalsolventtotheflaskandheattoboiling.B.Removefromheatandallowsolutiontojuststopboiling.C.Obtainaboutone-halfspatula-fullofdecolorizingcarbon.D.Addthedecolorizingcarbon.E.Heatthesuspensiontoboilingforabout5minutes.F.Performahotgr__ityfiltration.G.DoA-Dunder“BestCase”.PerformingaHotGr__ityFiltration

1.Fan-foldapie__of11cmfilterpaperasdemonstratedinpre-lab.

2.Chooseabeakerthatisatleasttwi__thevolumeastheamountofrecrystallizationsolventyouareusing.

3.AddafivemLsofnewrecrystallizationsolventtothebeakerpla__thestemlessfunnelonthebeakerandheatthesolventtoboiling.

4.Pla__yourfan-foldedfilterpaperinthefunnel.Pourthehotrecrystallizationsolutionalittleatatimeintothefilterpaperbeingcarefultonotmissthefilterpaper.Keeptherecrystallizationsolutionhot.

5.Afteralloftherecrystallizationsolutionhasbeenpouredintothefilterpla__afewmLsofrecrystallizationsolventintheflaskheatittoboilingandpouritintothefilter.

6.Carefullyremovethehotfiltrationassemblyfromthehotplateandallowittocooltoroomtemperature.DoA-Dunder“BestCase”.

7.S__ethefilterpaperandthe__terialinit.YouwillTLCitalongwithyourcropsofcrystals.Allowtherestofittodrythenweighit.BeakerStemlessFunnelFan-FoldedFilterPaperCompleteAssemblyThin-LayerChro__tographyTLCofUnknownRecrystallizationProductsInthisexperimentyouwillbeassessingthepurityofyourcropsofrecrystallizedunknown.Yourunknownisbiphenyldibenzala__toneorbenzoicacid.Yourunknownhasvariousimpuritiesaddedtoit.Sin__theunknownsallshowupunderUVlightwecaneasilydetectthemwithTLC.BiphenylBenzoicacidDibenzala__tonePro__dure:ObtaintwospottingcapillariesandaTLCplateanddrawalightpencillineacrossthewidthoftheplateabout1cmfromtheedge.Pla__5light“tic__rks”onthelineapproxi__telyequallyspa__d.Inseparatetest-tubesdissolvetinyamountsoftheimpuritiesfromthehotfiltrationnote:alloftheimpurities__ynotdissolveandyourrecrystallizedproductinabout1mLofa__tone.Usingoneofthespottingcapillariesyou__despotatinydropofthea__tonesolutionofyourimpuritiesonthesecondfromtheleft“tic-__rk”-you__ywanttopracti__spottingonapapertowelortissueto__ke__allspots.Allowittodryandthenchecktheplateunderashort-w__eUVlighttoseeifyouh__eavisiblespot.Ifnotspotyoursolutionagainonthesame“tic-__rk”.Donotspotanymoretimesthanneeded-toomuch__terial__ygiveresultsthatarehardtointerpret!Usingadifferentcapillaryspotthesolutionofyourunknownontheleftmost“tic-__rk”.Afteryouh__eyoursamplesspottedtakeyourplatetothestandardsinthehoodandspotbenzoicacidonthemiddle“tic-__rk”dibenzala__toneonthesecondtorightmost“tic-__rk”andbiphenylontherightmost“tic-__rk”.Donotgetthespottingcapillariesforthestandardscontaminated!CheckthespotsundertheUVlighttoseeiftheyareallvisible.Toprepareadevelopingchamberobtainapie__of11cmfilterpaperandfolditabout1inchfromtheedgetoobtainaflatedge.Pla__thefilterpaperflatedgedowninyour400mLbeaker.Obtain10mLoftheTLCsolventandpouritintothebeakerswirlingthebeakertowetthefilterpaperwiththesolvent.Carefullypla__theTLCplateinthedevelopingchamberspottedsidedowntryingnottosplashthesolventontheplate.Thelevelofsolventmustbebelowthepencilline.Coverthebeakerwithawatchglass.Thesolventwillriseupthroughthestationaryphaseontheplate.Whenthesolventhasrisento1-2cmfromthetopoftheplateremovetheplateanddrawalightpencillineacrosstheplateattheleveltowhichthesolventrose.Allowthesolventtoevaporatew__ingtheplateintheairwillspeedthisupandthenlookattheplateundertheUVlight.Circleallofthespots.Youwillidentifythecomponentsofyourunknowntabletbycomparingtheamountsthecomponentstr__eleduptheplatewiththeamountsthestandardstr__eled.TheseamountsarereportedasRfretentionfactorvalues.XDistan__thespottr__eledRf=---=------------------------------------YDistan__thesolventtr__eledMeasurethedistan__aspotmovesfromthe__nterofthespot.CleaningUpWhenyouarefinishedwiththeexperimentpourtheTLCsolventinthe“RecoveredTLCSolvent”container.Thefilterpaper__ybethrownawayinthetrashcan.Usedspottingcapillariesshouldbepla__dinthe“CleanBrokenGlass”container.Youra__tonesolutionsyouusedtospotwith__ybeflusheddownthesinkwithlotsofwater.LabReportFor__tPurificationofanUnknownCompoundbyRecrystallizationMinilab3IdentificationoftheUnknownCompoundbyThinLayerChro__tographyandMeltingPoint

1.TitlePageA.Adescriptivetitlewithbetween15-25words.B.Datestheexperimentwasperformed.C.Courseandsectionnumbers.D.Yourname.E.TapeyourTLCplatetothebottomofthepage.LabeleachcolumnofspotssoIknowwhatiswhat.

2.BodyofthereportforRecrystallizationofanUnknownstartanewpageA.Unknowncompoundnumber.B.Resultsofsolubilitytestsinthedifferentsolvents.Sum__rizetheresultsinaneattable.C.Bestrecrystalizationsolventfound-explain.D.Weightofcompoundusedforrecrystallization.E.Meltingpointrangeofunknownbeforerecrystallization.F.Weightofrecrystallizedunknown.G.Meltingpointrangeofrecrystallizedunknowncompound.H.Calculatetheper__ntrecoveryoftheunknown.Showyourwork.I.CalculatetheRfvaluesofeachofthespotsonyourTLCplate.Showyourwork.

3.QuestionsA.WhatistheidentityofyourunknownsolidExplicitlyexplainyourreasoningusingthedatayouacquired.B.AfteryourecrystallizedyourunknownwasitpureExplain.WhatimpuritieswerelikelypresentWhateviden__doyouh__eforthemC.Howwelldidyouperformyourhotgr__ityfiltrationExplainyourreasoning.25。