The purpose of this experiment is to analyze mixtures of compounds prior to, during and after a separation scheme. This experiment also allows monitoring reactions of organic molecules, and determines the identity of a mixture of compounds.
STRUCTURES AND PHYSICAL PROPERTIES OF REACTANTS
| a. Hexane1Molecular Molarity: 86.18 g/molBoiling Point: 69 ºCMelting Point: -95ºCDensity: 0.659 g/mL at 25ºCWater Solubility: Insoluble in waterColor/Texture: Colorless/LiquidHazardous Information: May cause irritation to the eyes, skin and respiratory system. May cause drowsiness and/or dizziness. Suspected of damaging fertility or unborn child. May cause damage to organs. Toxic to aquatic life. Highly flammable liquid and vapor. May be fatal if swallowed.Structure: CH3(CH2)4CH3
| b. Methanol2Molecular Molarity: 32.04 g/molBoiling Point: 64.7ºCMelting Point: -98ºCDensity: 0.791 g/mL at 25ºCWater Solubility: Completely miscibleColor/Texture: Colorless/LiquidHazardous Information: Highly flammable liquid and vapor. Toxic if swallowed or in contact with skin. Causes skin and eye irritation. Causes damage to organs.Structure: CH3OH
| c. Methylene Chloride3Molecular Molarity: 84.93 g/molBoiling Point: 39.8-40.0ºCMelting Point: -97ºCDensity: 1.325 g/mL at 25ºCWater Solubility: Slightly soluble in waterColor/Texture: Colorless/LiquidHazardous Information: Harmful if swallowed. Causes skin and eye irritation. Suspected of causing cancer.Structure: CH2Cl2
| 2. Possible Components of Mixture
| a. Biphenyl4Molecular Molarity: 154.21 g/molBoiling Point: 255ºCMelting Point: 68-70ºCDensity: 0.992 g/cm3Water Solubility: 0.0075 g/L at 15ºCColor/Texture: Light yellow/CrystallineHazardous Information: May be harmful if swallowed. Causes skin and serious eye irritation. May cause respiratory irritation. Very toxic to aquatic life.Structure: C12H10
| b. Benzophenone5Molecular Molarity: 182.22 g/molBoiling Point: 305ºCMelting Point: 47-51ºCDensity: N/AWater Solubility: N/AColor/Texture: White/CrystallineHazardous Information: May be harmful if inhaled. May cause respiratory tract irritation. May be harmful if absorbed through skin. May cause skin and eye irritation. May be harmful if swallowed.Structure: C13H10O
| c. Benzhydrol6Molecular Molarity: 184.23 g/molBoiling Point: 297-298ºCMelting Point: 65-67ºCDensity: N/AWater Solubility: N/AColor/Texture: Crystalline/whiteHazardous Information: May be harmful if swallowed. Causes skin and serious eye irritation. May cause respiratory tract irritation.Structure: C13H12O
The experiment began with three elution chambers prepared using 150 mL and 250 mL beakers. One filter paper was placed inside each beaker. Enough hexane was added to the bottom of the first beaker, methylene chloride in the second beaker and methanol to the third beaker. The beakers were marked with the identity of the solvents. The filter papers inside the beakers were wet using the respective solvents then covered with aluminum foil. Three small TLC plates were obtained, carefully held on the edges to avoid contamination from fingers, and placed under a UV lamp to verify that there are no impurity spots on them. At approximate 4mm above the edge of the bottom of the TLC plates, a line was drawn across each one with an “X” in the middle of the line in each one indicating an origin. The plates were visually checked to ensure that the silica gel was not disturbed. A single spot of the known mixture was placed on the origins using a capillary tube. The known mixture contains: Biphenyl, Benzophenone, and Benzhydrol. The solvent was set aside to evaporate then placed under the UV lamp once again to see if a dark spot is present in each plate. The plates were then placed in each of the beakers prepared earlier; one plate in the hexane eluting chamber, another plate in the methylene chloride eluting chamber and the last plate in the methanol eluting chamber. The beakers were closed loosely...
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2MSDS. Rep. no. 34860. N.p.: n.p., n.d. Sigma Aldrich. Sigma Aldrich. Web. 14 Oct. 2012. <www.sigmaaldrich.com>.
3MSDS. Rep. no. 270997. N.p.: n.p., n.d. Sigma Aldrich. Sigma Aldrich. Web. 14 Oct. 2012. <www.sigmaaldrich.com>.
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5MSDS. Rep. no. 427551. N.p.: n.p., n.d. Sigma Aldrich. Sigma Aldrich. Web. 14 Oct. 2012. <www.sigmaaldrich.com>.
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Benzhydrol can be synthesized from Benzophenone via a reduction reaction. Samples of the reaction mixture are taken at several times during the reaction (start, 50% of the way and at the end of the reaction time). Draw the anticipated results (spots) for silica gel TLC plates at the specified reaction (not elution) times (assume the best solvent used above):
At start (no reaction) At 50 % completion At 100 % completion
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