Experiment 9 - Medina PDF

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Experiment 9: Column Chromatography- Separation of a Mixture of Ferrocene and Acetyl Ferrocene

Abstract Column chromatography is a separation method which is very similar to Thin Layer Chromatography (TLC) which takes advantage of compounds’ differing abilities to absorb and to

travel down normally a polar stationary phase consisting of silica. Ferrocene can be converted to acetylferrocene by acylation reaction. In column chromatography, compounds move down and through columns by force of gravity. The different rates of compound separation is dependent on factors that include compound’s overall polarity. Polar compounds will stick to the stationary phase longer than less polar or non-polar compounds. The purpose of this experiment is to separate a mixture of ferrocene and acetylferrocene using column chromatography. As a result of dirty columns, the order of the color bands ended up being yellow, orange, red instead of orange, yellow, red which led to some error. The Rf for ferrocene was 0.67 while acetylferrocene was 0.5. For percent recovery, 8.67% acetylferrocene was recovered and 29.33% ferrocene was recovered.

MSDS 

Silica Gel o Chemical Formula: SiO2 o State: Solid

Molecular Weight: 60.08 g/mol Health: 2 Boiling Point: 2,230C Fire: 0 Melting Point: 1,710C Reactivity: 1 Density: 2.65 g/cm3 Hazards: Substance may cause eye, skin, digestive tract, and respiratory tract irritation Hexane o Chemical Formula: C6H14 o State: Liquid o Molecular Weight: 86.16 g/mol Health: 2 o Boiling Point: 62-69C Fire: 3 o Melting Point: -95C Reactivity: 0 o Density: 655 kg/m3 o Hazards: Substance may cause eye and skin irritation. Fatal if ingested and extremely hazardous if inhaled. Methylene Chloride o Chemical Formula: CH2Cl2 o State: Liquid o Molecular Weight: 84.93 g/mol Health: 2 o Boiling Point: 39.6C Fire: 1 o Melting Point: -97.7C Reactivity: 0 o Density: 1.33 g/cm3 o Hazards: Substance may cause eye, skin, respiratory tract, and gastrointestinal irritation. Ethyl Acetate o Chemical Formula: C4H8O2 o State: Liquid o Molecular Weight: 88.11 g/mol Health: 1 o Boiling Point: 77C Fire: 3 o Melting Point: -83C Reactivity: 0 o Density: 902 kg/m3 o Hazards: Substance may cause eye, skin, digestive tract, and respiratory tract irritation Ferrocene o Chemical Formula: C5H5 o State: Solid o Molecular Weight: 186.04 g/mol Health: 2 o Boiling Point: 249C Fire: 2 o o o o o

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Reactivity: 1

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1.) 2.) 3.) 4.) 5.)

o Melting Point: 172.5C o Density: 1.11 g/cm3 o Hazards: Eye, skin, digestive tract, and respiratory tract irritaton Acetylferrocene o Chemical Formula: [Fe(C5H4COCH3)(C5H5)] o State: Solid o Molecular Weight: 228.07 g/mol Health: 4 o Boiling Point: 161C Fire: 1 o Melting Point: 81C Reactivity: 0 o Density: 1.01 g/mL o Hazards: Substance may be fatal if swallowed. Substance is toxic to the skin, harmful if swallowed, and may cause eye irritaton Toluene o Chemical Formula: C7H8 o State: Liquid o Molecular Weight: 92.14 g/mol Health: 2 o Boiling Point: 110.6C Fire: 3 o Melting Point: -95C Reactivity: 0 o Density: 867 kg/m3 o Hazards: Substance may cause eye, skin, and respiratory tract irritation. Fatal if ingested. Ethanol o Chemical Formula: C2H5OH o State: Liquid o Molecular Weight: 46.04 g/mol Health: 2 o Boiling Point: 78C Fire: 3 o Melting Point: -114C Reactivity: 0 o Density: 790 kg/m3 o Hazards: Substance may cause eye and skin irritation. Fatal if ingested and hazardous if inhaled. Procedure To the column, place a small piece of glass wool if needed to serve as a semi-porous plug Add just enough sand to cover the glass wool plug to keep it weighted down Measure 13 mL of flash chromatography silica gel into a 25ml graduated cylinder. Add this to a separate dry Erlenmeyer flask Add just enough hexane to create a loose flurry, use a stirring rod of mix Pour the slurry through the column with the stopcock open and over another dry Erlenmeyer flask to collect the mobile phase that passes through the glass wool or frit.

6.) 7.) 8.) 9.) 10.) 11.) 12.) 13.) 14.) 15.) 16.) 17.) 18.) 19.) 20.) 21.) 22.) 23.) 24.) 25.) 26.)

Add a bit of sea sand to form a thin layer just above the silica with the stopcock closed Label 3 100 mL beakers 1,2,3 Add .1500g of crude sample to the column Add 0.5g silica Fill the column to the top with hexanes Open stopcock and allow to run continually Collect colorless eluent in a waste beaker When the first color band is 1cm from the bottom of the column, collect the fraction in beaker 1 Once done, change the eluting solvent to 10:1 hexane-ethyl acetate Collect the intermediate fraction into beaker 2 Once done, change eluting solvent to 1:1 hexane-ethyl acetate Collecting remaining fraction until stationary phase is white Transfer fraction 1 to a small wide mouthed beaker that is pre-tared Rinse beaker from fraction 1 with small amounts of hexane Repeat steps 18-19 for fraction 3 (beaker 3) Evaporate the solvent from fraction 1 and 3 over a hotplate under the fumehood Weight the two round bottom flasked containing the soilds from fraction 1 and 3 Dissolve each solid in separate flasks with 2ml of methylene chloride Spot each on a TLC plate Also spot ferrocene and acetyl ferrocene Develop plates with 30:1 toluene-ethanol

Data Mass of Contents in Beakers After Boiling Beaker 1 (Ferrocene) Beaker 2 Beaker 3 (acetylferrocene) .044g .013g TLC Plate 6 5 4 (Orange; Ferrocene) 3 (Red; acetylferrocene) 2 1 0

Rf Values of Ferrocene and Acetylferrocene Ferrocene Literature Value Actual Value 0.9 0.67

Acetylferrocene Literature Value Actual Value 0.53 0.50

Notes/Observations For this lab, the columns were pre-made to make the experiment go by faster, however, since the columns were dirty, it caused our compounds to not separate and move down the column at the same time. This lead to the color bands being out of order, instead of orange, yellow, red, the bands were yellow, orange, red. . Calculations Distance spot moved Distance Solvent moved 4−0 =0.67 Rf ( ferrocene) = 6−0 3−0 Rf (acetylferrocene)= =0.50 6−0 Rf =

Pe rcent Recovery =

Purified Mass x 100 Crude Mass

.044 x 100=29.33 % .1500 .013 Percent Recovery Acetylferrocene= x 100=8.67 % .1500 Percent Recovery Ferrocene=

Conclusion Overall, the experiment had some successful since crude product was recovered in small amounts with relatively close Rf values to the actual values. The Rf for ferrocene was 0.67 while acetylferrocene was 0.5. The actual Rf of ferrocene was 0.9 while the actual value for acetylferrocene was 0.53. For percent recovery, 8.67% acetylferrocene was recovered and 29.33% ferrocene was recovered. The columns were pre-made as well as used by other classes which caused them to be dirty which led to the separation not being accurate since the order of

the colored bands switched. At times, the eluting solvent was not changed or had yielded a clear liquid which could of also effected the results. Pre and Post-Lab Questions 1.) You run a column chromatography separation and notice many fixed fractions coming off. Name three conditions you could employ to create a better separation the next time you run the column on this crude compound. 1.) Decrease polarity of the solvent 2.) Alter size of the column 3.) Adjust rate flow using stopcock 2.) For the following compounds, 1,4-dimethyl benzene (para-Xylene), methoxybenzene (anisole), and Benzoic acid, provide a relative ranking of the order of elution 1.) Benzoic Acid 2.) Methoxybenzene (anisole) 3.) 1,4-dimethyl benzene (para-Xylene) 3.) What are the dangers of mishandling silica gel? Silica gel is extremely hazardous. Silcia gel may cause eye, skin, respiratory tract, and digestive tract irritation. 4.) If the compounds that are eluting are not visible with the naked eye, what two methods should you employ to visualize the fractions by TLC? If a TLC cannot be seen with the naked eye, one can use a UV light or using stains like iodine.

References Fisher Scientific SDS Search Chemistry Lab Manuel...