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Midterm Rules: Cell phones off and in your pack. Do bring a calculator, but not a "computer". No sharing ...

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Midterm Rules: Cell phones off and in your pack. Do bring a calculator, but not a "computer". No sharing ...

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  1. Today:Exp.6: Column Chromatography: The Separation of Ferrocene and Acetyl FerroceneMidterm next Fridayin your lab!starting at the beginning of your lab session5 Problem Sets (Total 100 pts.)The exam will include today’s Exp. 6 materialReview/study lab lectures, practice questions, experiments, calculations, graphs.Do sample Midterm questions in ERES file

  2. Midterm Rules: Cell phones off and in your pack. Do bring a calculator, but not a "computer". No sharing ... Do not leave the room during the exam. No extra note paper; use back of pages if necessary. Please no questions during exam (unless you discover a serious mistake). You can write: "if I understand the question this way ..." No "late" exams... A midterm not taken earns the grade "F". Read questions carefully. Proofread….

  3. Exp.6: Column Chromatography: The Separation of Ferrocene and Acetyl Ferrocene(omit UV/VIS analysis) 1) Comment on the polarity of these two compounds. 2) Ferrrocene and Acetylferrocene are metal organic compounds. Do you know other metal organic compounds? Are there any in nature?? 3) What is the color of ferrocene? Of acetyl ferrocene? What features in their molecules lead to absorption of light within the visible range (colored!).

  4. Exp.6: Column Chromatography: The Separation of Ferrocene and Acetyl Ferrocene Cyclopentadienyl anion is “aromatic”. What makes it aromatic?

  5. Column Chromatographyfollowed by Thin Layer Chromatography (TLC) What is common to all methods of chromatography? In our experiment: Stationary phase: Alumina III Moving phase: Pet. Ether. Later: 50/50 mixture pet. ether/diethyl ether

  6. Column Chromatography

  7. Setting up the micro-scale Column Chromatography (CC) • Procedure: • Assemble column. Check flow through the frit by using petroleum ether. Then bring the pet ether volume to a height of ¾ the column. • Slowly add Alumina powder. Goal is to have uniform packing. Do not let the top of the column packing go dry. • Add ~1 cm of sand after the column settled. (What could be the purpose of doing this?)

  8. Funnel Column ChromatographySet up Alumina Stationary Phase Tare

  9. Separation of your mixture by CC • Save a small amount of unknown sample in the original vial for TLC. • Dissolve the weighed unknown in minimum of methylene chloride • Start pet ether flow through column and stop when solvent is just barely above the sand. Gently add your unknown sample with a pipette along the wall of the column • Elute ferrocene with petroleum ether (Do Not let the column go dry). Collect the yellow ferrocene band in a tared 50-mL E-flask.

  10. 4. To collect acetyl ferrocene, switch to a new tared 50-mL E-flask, add 50/50 petroleum ether/diethyl ether to column and start eluting the orange band of acetylferrocene. 5. Slowly evaporate the solvents in each of the E-flask on a steam cone or a sand bath. Weigh residues!

  11. Evaluation of samples byThin Layer Chromatography (TLC) TLC plate (Silica is the stationary phase) 0.5 cm from top Lightly mark with pencil, then spot samples . . . 1 cm from bottom origin Mix Fe Ac

  12. TLC Developing Jar TLC eluent (moving phase!) : (30:1) toluene/absolute ethanol Make sure that eluent level is below the spots Allow moving phase run up the plate to top line (NOT to top edge!), then remove TLC

  13. Mark solvent front with pencil immediately after removing from developing chamber. Dry TLC and draw a circle around each spot. TLC plate showing good separation: solvent front origin

  14. Calculate Rf –values for each spot Where would you find the spot of a sample with an Rf value of 0.1, of 0.5, of 0.9? How about an Rf-value of 1.3 ???? B A A . . . Rf = B

  15. See also FSN link on my Home Page http://userwww.sfsu.edu/~msequin/ ACSFamily Science Night Willard Middle School in Berkeley Thursday, Oct. 26, 6:30 – 8:30 pm • What would you do? • Help set up experiments • Help middle school students (and their parents) do the experiments • What would you get? • experience in working with youngsters and showing them the fun of science • a nice entry on your resume • a good impression with your instructor!

  16. Next Friday Lab Lecture:Your questions….Remaining Experiments:Exp.8, “Dehydration of 2-Butanol”; GCExp.9, “Separation and Identification of an Unknown Mixture” (3 lab periods); IR, recryst., mp.s and other techniques you learnt this semester

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