SC CHEM 333 - Simple Distillation of Organic Molecules Pre-Lab (6 pages)

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Simple Distillation of Organic Molecules Pre-Lab



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Organic Chemistry 333L section 001 Laboratory Pre Lab Simple Distillation of Organic Molecules By Cameron Kahn 14 January 2019 TA James Collie Simple Distillation of Organic Molecules Object In this experiment he she will learn how to set up a simple distillation apparatus He she will use an unknown organic compound to do the distillation process Two methods of distillation will be used the use of a condensing column and the use of a fractionating column The recorded temperatures and volumes will be plotted against each other on graphic paper or excel This will show the boiling point of the unknown molecule Based upon the resulted boiling point the unknown ketone will be identified The purpose of the experiment is to show a simple purification process and two methods of separating liquids and then identifying the compound in question using the recorded boiling point Theory In the liquid phase ionic attraction hydrogen bonding dipole interactions and van der Waals forces hold the molecules together When these attractions are overcome the liquid will vaporize which in turn will become a gas To overcome these attractions the temperature at which the vapor pressure of the liquid equals the pressure exerted upon the surface of that liquid is the boiling point of that liquid Atmospheric pressure suppresses the liquid so energy in the form of heat is required to increase the kinetic energy and therefore overcomes this pressure thus causing the liquid to boil CITATION Geo12 l 1033 Liquids can have impurities which causes the boiling point to have a greater range This effect is due to how the impurities interact with the compound that is being measured Finding the boiling point of a liquid is harder than finding the melting point of a compound In addition if a liquid has a constant boiling point it has a higher probability of being pure This is not always true Two or more miscible liquids mixed together will have the exact same boiling points Other factors that can cause the boiling point to vary in temperature are the shape molecular weight applied pressure and polarity of the molecule The addition of solute will interfere with vapor pressure causing an increase in boiling point The best method of separating chemicals by boiling point is the distillation method Distillation is a widely used method for separating mixtures based on differences in the conditions required to change the phase of components of the mixture Distillation To separate a mixture of liquids the liquids must have a difference in boiling points of at least 20 degrees Celsius Increasing the heat exerted on the mixture will cause the liquid in the mixture with the lower boiling point to vaporize first The liquid in the vapor phase will travel through the condensing column to the connecting flask where it will collect back into liquid form The new flask will hold mostly the liquid with the lower boiling point however in order to purify the liquid more another distillation must be performed Repeating the process on the collected liquid will improve the purity of the product this process is called double distillation CITATION Abo13 l 1033 The two methods used in the experiment will be carried out with the same theory however the use of the fractionating column to do a fractional distillation will operate slightly different when compared to simple distillation In fractional distillation the mixture in question will be heated and the liquids will begin to change into the vapor phase through a series of theoretical plates or simple distillations located in the fractionating column The vaporized liquid will then condense back to a liquid once it reaches certain levels within the column As more vapors move up the column they will heat the condensed liquid to vapor form again and thus travel further up the column Each time this occurs the liquid is becoming more pure This process is like doing multiple simple distillations in one process called fractional distillation Procedure Part A Simple Distillation of Organic Molecules Start by assembling the apparatus as shown in figure 1 Now place 15 mL of unknown in a dry 25 mL round bottom flask and add one boiling stone Next heat the solution by setting the variac between 70 and 75 Once boiling is achieved lower the variac to 50 Record the temperature at 0 5 mL increments until 12 mL of distillated product is collected Then stop the distillation He she will then use the recorded data to plot temperature vs volume of distillate Make sure to connect all the dots Attempt to determine the boiling point from the graph and identify the unknown from the determined boiling point Identification of the unknown substance will be based on the comparison of the measured boiling point to actual boiling points giving in a table Procedure Part B Fractional Distillation Place 8 mL of cyclohexene and 8 mL of n butyl acetate in a newly clean and dry round bottom flask Make sure to add one boiling chip Set the variac between 70 and 75 for the initial setting once boiling achieved lower to 60 Record the temperature during the entire distillation and every 0 5 mL CITATION Geo12 l 1033 Once you have collected approximately 5 mL of distillated product place in a graduated cylinder This will be you first product Replace the graduated cylinder and collect another 3 to 4 mL of distilled product and then set this aside Ali Next you will need to collect approximately 4 mL of distilled product again and record the temperature in 0 5 increments This is your second product Use the recorded data to plot temperature vs volume of distillate temperature as function of volume Make sure to connect all the dots Attempt to determine which product would boil first Record the findings Apparatus Part A see figure 1 25ml round bottom flask Sidearm adapter Thermometer with adapter Distilling or condensing column 10mL graduated cylinder Two ring stands Grease for air tight seals Heating mantle and variac Figure 1 Distilling Apparatus Keck clamps Hoses Part B Same apparatuses as Procedure 1 except you will need a Fractionating Column and two 10mL graduated cylinders Figure 3 Fractionating Column apparatus Figure 2 Fractionating Column Chemical Table Part Name Structure MW g mol Melting Point oC Boiling Point oC Density g mL 82 14 103 5 83 0 811 116 15 74 124 126 0 88 98 14 42 101 5 0 814 32 04 98 64 6 0 791 C6H10 Cyclohexene C6H12O2 n Butyl Acetate C6H10O Diethyl Ketone CH3OH Methanol Reminder Diethyl ketone and methanol are only


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