资源描述:
《Stains-for-Developing-TLC-Plates(薄层层析显色剂).doc》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、StainsforDevelopingTLCPlates OnceaTLChasbeendeveloped,itisfrequentlynecessarytoaidinthevisualizationofthecomponentsofareactionmixture.Thisistrueprimarilybecausemostorganiccompoundsarecolorless.Frequently,theorganiccompoundsofinterestcontainachromophorewhichmaybevisualizedbyemployingei
2、therashortoralongwaveUVlamp.Theselampsmaybefoundaspartofastandardorganicchemistryresearchorteachinglab.Typicalexamplesoffunctionalgroupswhichmaybevisualizedthroughthismethodarearomaticgroups,a,b-unsaturatedcarbonyls,andanyothercompoundscontainingextensivelyp-conjugatedsystems.Whileexposi
3、ngtheseTLCplatestoUVlight,youwillnoticethatthesilicagelwillfluoresce,whileanyorganicmoleculewhichabsorbsUVlightwillappearasadarkbluespot.Circlingthesespotsgentlywithadullpencilwillpermitaninitialmethodforvisualization.Fortunately,thereareanumberofpermanentorsemi-permanentmethodsforvisual
4、izationwhichwillnotonlyallowonetoseethesecompoundsbutalsoprovideamethodfordeterminingwhatfunctionalgroupsarecontainedwithinthemolecule.ThismethodisreferredtoasstainingtheTLCplate,andexperiencewillallowyoutodeterminewhatfunctionalgroupswillappearaswhatcoloruponvisualization.Followingisali
5、stingofthemostcommonlyemployedstains,thekindofcompoundsforwhichthey'reusuallyemployed,andatypicalrecipe.ANoteonTLCPlates Althoughitshouldbeobvious,besurethatthekindofTLCplateyouareusingiscompatiblewiththestainortheconditionsforitsdevelopment. Forinstance,theinexpensiveplatesusingaplast
6、icpolymerbackingcannotbeusedforstainsrequiringheatfordevelopment. Glassbackingisfineforthis,butthesilicagelistypicallynottightlybondedtotheglass,andtendstobeinadvertantlyscrapedoffveryeasily;thus,thesearenotsuitableforstoragefollowingdevelopment. Inourgroup,weusealuminum-backedplates,whi
7、charelessexpensivethanglass,areheat-impervious,thesilicagelisverytightlyboundtothebacking,andaresothinthat,ifdesired,aparticularlyspectacularplatecanbetapedintoyourlabnotebook.TheStainListIodineThestainingofaTLCplatewithiodinevaporisamongtheoldestmethodsforthevisualizatio