organic chemistry Activity: Column Chromatography Fe diacetylferrocene acetylfer
ID: 503787 • Letter: O
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organic chemistry Activity: Column Chromatography Fe diacetylferrocene acetylferrocene ferrocene (dark red) orange) (yellow) The compounds in this experiment are convenient because they are colored and can be observed on the column easily. Ferrocene and its derivatives (above) are called "sandwich compounds" discovery and structural confirmation won the nobel prize in 1973 for wilkinson and Fischer All waste in this lab MUST BE PLACED IN A SPECIAL FERROCENE wASTE CONTAINER (fume hood) Procedure: 1. Obtain 020 g of ferrocene mixture and place in a small beaker. Add a spatula tip the (about 12 mg) of alumina powder to your small beaker with ferrocenes. Add just enough hexane/ethyl acetate (column solvent #2) to dissolve the ferrocenes and then stir the solution to dryness with a spatula. the following 2. Build your column according to the instructions on page 1. Also, obtain solvents in separate containers: 5 mL hexane, 10 mL of 7o/30 (hexane/ethyl acetate), and 5 mL of 95/5 (CH2Clz/CH3OH) 3. Begin the separation by using hexane as your mobile phase. You will see a yellow band running down the column. When this band begins to elute (or drain), collect it in a clean vial. Make sure you only collect this band it must be kept pure. If your bands are overlapping, they should be placed in a waste beaker. Throughout this experiment, IT IS MPORTANTTO CONTINUALLY ADD SOLVENT so THE coLUMN DOES NOT DRY OUT 4. When all of the yellow band has eluted, change your solvent system to a 70/30 mixture of a acetate. The orange band should begin to move faster. Collect this band in clean vial. Be careful to only collect this band, and not the darker red band 5. After the orange band has eluted, change your solvent system to 95/5 methylene chloride/methanol. Collect the last red band in a vial the hot 6. Prepare your fraction vials for TLC analysis by evaporating some of the solvent using plate in the hood. This will concentrate your fer for visual analysis, 7. Assess the purity of your fractions using TLC. spot each fraction on the plate with your starting mixture already spotted. Run this plate using 70/30 hexane/ethyl acetate as a TLC solvent. Circle the spots, and have your instructor grade the plate in lab! Re-draw the plate below, calculating the Rfvalues.Explanation / Answer
1. Diacetylferrocene is the most polar compound based on its structure. As we can see polarity in this case is governed by electronegative atom, and diaacetylferrocene has two Oxygen atoms. Resulting in more polarity.
2. We begin with nonpolar solvent because their nonpolarity result in less interactions with TLC stationary phase. Which in turn result into farther movement from start. Polar solvents progress is hindered and they cant travel farther. This gives us the resolution if we begin with nonpolar solvents.
3. Same factors govern the movements of the compound.
In the TLC , the solvent moves upward by capillary action, serving as the mobile phase. The layer of alumina gel on its surface, serving as the stationary phase.
In the column chromatography apparatus, the top layer of sand prevents the solvent (mobile phase) from disturbing the adsorbent (which is the stationary phase) when it’s poured in. The bottom layer of sand provides a level surface to keep the adsorbent layer uniform.
4.
Affinity is a qualitative measurement of the attractive force between a compound and a phase. Polar solvents have high affinity for polar compounds and nonpolar have high for nonpolar ones.
Ferrocene is nonpolar just like hexane.
Acetylferrocene is polar with nonpolar ring structures. Therefore it is with mixture of Polar+nonpolar solvents (hexane+ethyl acetate)
Diacetylferrocene is the most polar, therefore has polar solvent.
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