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Homework answers / question archive / General Elution Procedure: Procedure Dissolve the residue from Experiment 3 with 0

General Elution Procedure: Procedure Dissolve the residue from Experiment 3 with 0

Chemistry

General Elution Procedure: Procedure Dissolve the residue from Experiment 3 with 0.5 mL ofCl-izClz (the amount is not important, use about 1/2 a Pastuerpipette full) within the roundbottomed ?ask. Weigh out 0.3 g of silica gel (70-230 mesh) on the top-loading balances and add this to the CHzClz solution of thereaction residue in the round-bottomed ?ask. Evaporate the solvent on the rotavap until a dry red—brownsilica powder remains. Now the mixture is adsorbed on thesurface of the silica.Add 7.0 cm of fresh,new silica gel (70-230mesh) to your chroma-tography column. Tapthe column on thebench lightly to makesure all the materialhas settled. Clamp the column tothe support in your 71cm ol sand hOOd' l'lllX'llllF.‘ DI ill:Carefully add the prod-uct—adsorbed silica prepared above as alayer on top of the sili-ca contained in thecolumn. Carefully add ~1.0 cmof sand to the top ofthe column. Youshould now have a 7.0cm high, white layer of silica in the column, about ~1.0 cm ofa red-brown silica layer (your product mixture is adsorbedhere) topped by ~1.0 cm of sand. Clean out both of your round—bottomed ?asks (25 and 50-mL) and dry in the oven if necessary. Pre-weigh each ?ask.Elute the column with 12—15 mL of hexanes. Make sure theseptum capping the bottom of the column is removed. Use abeaker to collect what is called fore-run, the solvent ?rst elut-ed from the column that does not contain one of the prod-ucts. 1. Make sure you have acollection container un-der the column andcarefully ?ll the columnwith the eluting solvent.Be sure not to disturbthe sand layer while do—ing this. 2. Assemble the apparatusto pressurize the columnusing a dry piece of latextubing and a disposable ‘syringe. k 3. Pull back the syringe plunger and then push the otherend of the latex tubing over the top of the column care-fully. DO NOT DRAW BACK ON THE SYRINGEWHEN THE TUBING IS ATTACHED TO THE COL-UMN!!! 4. Slowly depress the syringe plunger. Allow the built uppressure to dissipate. 5. Remove the tubing from the end of the column and re-plenish the current eluting solvent. 6. Repeat steps 35 as necessary, changing the receivingcontainer and eluting solvent as needed. Part 1: Ferrocene Band Elution Using the General Elution \ Ferroce arid elufionProcedure described above, TR]elute the column with enough ”?ag... I”hexanes to fully collect the '2 -?rst yellow colored band(ferrocene). For most stu-dents, this is typically 12-15mL. Use a beaker to collectwhat is called fore-run, thesolvent ?rst eluted from thecolumn that does not containone of the colored products.Use the ?rst of the two pre-weighed flasks to collect theyellow band.Make sure that the yellowband has completely movedoff the column. NEVER LETANY PART OF THE STA- TIONARY PHASE GO DRYAFTER THIS POINT. Ace‘vlferrocene band elutr'on .. .

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