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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
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.
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!).
Cyclopentadienyl anion is “aromatic”. What makes it aromatic?
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
Column ChromatographySet up
Alumina Stationary Phase
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!
TLC plate (Silica is the stationary phase)
Lightly mark with pencil, then spot samples
1 cm from bottom
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
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:
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 ????
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
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