实验一 有机物熔点的测定ExperimentDetermination of melting point of organic matter.docx
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实验一 有机物熔点的测定ExperimentDetermination of melting point of organic matter.docx
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实验一有机物熔点的测定ExperimentDeterminationofmeltingpointoforganicmatter
实验一有机物熔点的测定(Experiment1Determinationofmeltingpointoforganicmatter)
Experiment1Determinationofmeltingpointoforganicmatter
Meltingpoint(melting,point)meansthetemperatureatwhichasolidphasecoexistswithaliquidatequilibriumatatmosphericpressureat1.Accordingtothisdefinition,theactualmeasurement,firstheatingamountofsolidpowdersampleincapillary,observingthespecimenfromtheinitialmeltingtemperaturerangetocompleteliquefaction.Thus,theresultingmeltingpointiscalledthepointmelting(capillary).Themeltingpointknowninthegeneralorganicchemistryliteratureisthemeltingpointofsuchacapillary.
Themeltingpointisimportantoneofthephysicalpropertiesofsolidmaterial,andcanbeusedfordetectionandidentificationofthepurityofthecompounds.Whensolidscontainimpurities,theyreducethemeltingpointandincreasetherangeofmelting,i.e.,thetemperaturerangefromtheinitialmeltingtothecompleteliquefaction.Thedeterminationofmeltingpointisoneofthebasicoperationsinorganicchemistryexperiment.
Themeltingpointofcommonlyoccurringsolidorganiccompoundsisshownintable1.1.
Table1.1meltingpointsofcommonsolidorganiccompounds
Compoundmeltingpoint(DEGC)
Benzoicacidbenzoicacid122.4
Ureaurea132.7
Cholesterolcholesterol148.5
Salicylicacid157~159salicylicacid
(fromThe,Merck,index,11th.ed)
Adevicethatmeasuresthemeltingpointusuallyhasthefollowingconditions:
Aconvenientheatsourceisneeded,andaBunsenburneroranelectricheaterisgenerallyused.
Theheatmediumusedmustbestableduringheatingtocontroltheriseorfallofthesampletemperature.Liquidswithhighthermalstabilityandhighboilingpointareoftenused,suchassiliconeoil,glycerin,orsaladoil,sothattheheatisdispersedevenlywithoutcausingtoomuchtemperaturechange.
Thetemperaturearoundthesampleshouldbeuniformsothatthesampletemperatureisconsistentwiththemeasuredtemperature.Thisisusuallydoneinagitatorsorconvection.
Adeviceformeasuringtemperatureusuallyusesathermometer,andthelowerpartofthethermometershouldbeascloseaspossibletothesample.
Ifasolidorganiccompoundisveryclosetopure,itsmeltingrangewillbeverynarrow,about0.5~1degreescentigrade.Butifimpuritiesarepresent,themeltingpointisloweredandtherangeisincreased.Therefore,thedeterminationofmeltingpointisnotonlyausefulmethodfortheidentificationofsubstances,butalsothemeltingpointisabasisforjudgingpurity.AssumethatacompoundBandcompoundA,themeltingpointofthesame,butisstillunabletoconfirmwhetherthesamekindofdesirablecompounds,asmallamountofBandAmixed,themixtureofthedeterminationofmeltingpoint;ifthemeltingpointofthesameasA,BandAforthesamekindofcompounds;ifthemeltingpointinA,youcanthatBandAarenotthesamekindofcompounds.
equipment
Eachframe1ironclamp2Bunsencapillarytube1Determinationof1seatmortarandpestle1setsofmeltingpoint(0.10~0.15cmdiameter,7cmlong)5glasstube(0.8x60cm)1spatula1thermometers(0~200c)1(withacorkthethermometerused)1rubberrings(fromoneendoftherubbertubeiscutto1)
Reagent
Eachgroup
Benzoicacid0.05grams
0.05gramsofsalicylicacid
Siliconeoil100ml.
Experimentalprocedure
Part1:
subjectexperiments
I.beforemeltingpointdetermination
Illustrationandillustration
Measuredbyacapillaryfortheendofthe1.lampheatingcapillarymeltingpoint,themeltingintosmallbeadsshapedclosed.
Whenheatingthecapillary,itshouldrotatethecapillaryatanytimesothatitcanbeheatedevenlywithoutbending.
Fillinthesampletobetested
Grindthetestsampleintosmallpowder,pouritoveracleansheetofwhitepaperandpileitup.
Theinvertedcapillary,theopeningisinsertedinthepowdersample,thesampleintothetube,thenthecapillaryupright(sealingendbelow).Accordingtofigure1.1,thecapillaryintotheglasstube,thebottomendofthecollisionbydesktop,gravityandinertia,thesamplepowderaccumulatedonthebottomofthecapillary.
Repeat
(2)stepstothesampleheightofabout2to4mm;eachspecimenisfilledwith3capillarytubes.
Figure1.1gravityloadingtest
Sample
Assemblyofameltingpointapparatus
Inthedeterminationofmeltingpointintothesiliconeoilpipe,theoilisnottoohigh,andtheironclampisfixedontherack.
(ifitisalreadyinstalled,itdoesnotneedtoberepeated)
Acapillarytubeofthefilledsampleisfixedtothethermometerwitharubberband,sothatthespecimenislocatedjustnexttothemercurybulbofthethermometer.
Afterthecorkhasbeendrilled,cutasmallnotchwiththeknife,asshowninfigure1.2.
Fig.1.2sectionaldrawingofcork
Athermometerwithacapillaryhavingbeenfixedtobetestedispassedintothecork,andthenthecorkisinsertedatthepointofdeterminationofthemeltingpoint.
Adjustthethermometerandthemeltingpointtodeterminethedistancebetweenthetubes,sothattherubberringislocatedontheoilsurface,donotimmerseitintheoil,asshowninFigure1.3,soastoavoidheating,rubbersofteningandloseelasticity.
Fig.1.3determinationoftemperatureandtemperatureofmeltingpoint
Distancerelationbetweendegrees
[note]tooperatethisexperiment,themeltingpointcanbereplacedbythefollowingsimplemeltingpointapparatuswithoutthedeterminationofthemeltingpointofFig.1-3.
A.placeda250mLbeakerinthehotironnet,builtinabout2/3ofthesiliconeoil,andotherfixed.
B.takeacorkandcutasmallnotchthroughtheholesothatitcanfixthethermometerandclearlyobservethetemperaturescale.
C.clampsthecorkandthethermometerwiththeironclamp,andadjuststhethermometerheight,causesthebottomendtobeabout3cmfromthebeakerbottom.
D.willbeabout35cmlongglassrod,madeinFigure1.4inabeaker,stirbar,upperandlowermixingsiliconeoilevenlyheated.
Fig.1.4simplemeltingpointmeasuringdevice
Two.Determinationofmeltingpoint
DirectdeterminationofmeltingpointtubeswithBunsenburner,asshowninfigure1.5.
Heatedtoatemperaturebelowthemeltingpointaboutthereferencevalueof15~20DEGC,adjustthesizeoftheflame,thetemperatureriseofthedegreeisnomorethan2perminuteto3DEGC;meltingpointtolowerthanthereferencevalueof2~4DEGC,thenslowdowntheperminuteriseof1degreesCelsiusormoreslowly.
Figure1.5meltingpointdeterminationdevicecarefullyobservedincapillaryreagentchangeandthechangeprocessofthethermometer;thephenomenon,asshowninfigure1.6.
Three.Sampletobetested:
benzoicacid(122.4DEGC)
Thetemperatureatwhichthesamplebegantosoftenandthetemperatureatwhichallthesolidspecimensmeltedintoliquidwererecorded.Thetwotemperatureiscalledthemeltingpointormeltingpointtest.
Figure1.6beforethemeltingpointofthecompound
Postphenomenonchangechart
Thesecondpart:
extendedexperiment
Themethodofdeterminingthemeltingpointoforganiccompoundshasbeenunderstoodbytheoperationofthesubjectexperiments.Thedeterminationofthemeltingpointofanunknownsubstancewillnowbemadetodeducethekindsofcompoundscontainedintheunknown.
Toobtaintheunknownfromteachers,designtheoperationsteps,conductthemeltingpointtest,andthenrefertoTable1.1themeltingpointofcommonsolidorganiccompoundsforfurtherinferenceandverification.
TheunknownsubstancereceivedisapuresubstanceormixtureHowtojudge?
Ifitisapuresubstance,whatisthecompoundlistedinthetable?
Ifitisamixture,whichtwocompoundsshouldbeincluded?
Whatconclusionscanbedrawnbyreferringtotheexperimentaldataobtainedbytheothergroups?
Experimentalreportonthedeterminationoforganicmattermeltingpoint
Dateofexperiment,date,date
Classnumber
Fullname
Nameofthesameclass
Experimentalpurpose
Part1:
subjectexperiments
Experimentalrecordsandresults
Determinationofmeltingpointofbenzoicacid
Thenumberofexperimentsbeginsatthemeltingtemperature(DEGC),thetemperatureatwhichthesolidiscompletelymelted(c),andthemeltingpoint(DEG)I,II,III
Problemsanddiscussion
Whatistheimportanceofmeasuringmeltingpoint?
Whydothespecimensinthecapillaryneedtobegroundintotinypowdersandtobetightlypacked?
Whenheatingthemeltingpoint,whyshouldtheheaterbeheatedatthelowerendofthebend?
Ifthemixedorganiccompoundsandasmallamountofslightlyhigherthanthemeltingpointofbenzoicacidinbenzoicacidinthemixture,themeltingpointofpurebenzoicacidandwhatisthedifference?
Thesecondpart:
extendedexperiment
(organizethestepsofthedesignandtheinferenceprocess,andrecordtheminsequence.)
TheunknownforthemeasurementofthemeltingpointisC,asapuresubstanceormixture?
Howtojudge
Broken?
Iftheunknownsubstanceisapuresubstance,whatisthecompoundlistedinthetable?
Ifitisamixture,whichtwocompoundsshouldbeincluded?
Whatconclusionscanbedrawnbyreferringtotheexperimentaldataobtainedbytheothergroups?
PhysicalchemistryexperimentsonSeniorTwo-1-PAGE3
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