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Lab 3: Separation of Liquids by Simple Distillation and Analysis by Gas Chromatography Zeba N. Siddiqui (Partner: Keti Berberi) September 23, 2014

Methods and Background The purpose of this experiment is to separate a mixture of Ethyl Acetate and Butyl Acetate into their pure compounds using simple distillation, information involving Ethyl Acetate and Butyl Acetate can be found in Table1. Each fraction obtained from the distillation will be analyzed through Gas Chromatography. Chromatography is a method for separating pure substances in a mixture. Separation is due to their affinity to the stationary or mobile phases of the chromatographic method. Specifically, Gas Chromatography, found in Figure 1, functions on the standard of separating the substances of a mixture between a mobile phase and a stationary phase. It is the technique that is used to separate mixtures of volatile compounds with boiling points that differ by less than 0.5◦C. It involves the vaporization of a mixture and then measuring that sample through a chromatographic column to figure out how much of the substance was actually vaporized. Different pure substances vaporize at different temperatures, known as fractions. In Gas Chromatography, the stationary phase is a liquid, while the mobile phase is a gas. This would be different for the Column and Thin-Layer Chromatography. In Column Chromatography and TLC, the stationary phase is solid and the mobile phase is liquid.

Figure 1: Gas Chromatography

Ethyl Acetate C4H8O2

Butyl Acetate CH3COO(CH2)CH3

Molecular Weight

88.11 g/mol

116.16 g/mol

Boiling Point

77.0◦C

126.5◦C

Molecular Formula Structure

Table 1: Molecular Formulas, Structure, Molecular Weights, and Boiling Points of Ethyl Acetate and Butyl Acetate.

Simple distillation permits separation of distillate from a less volatile substance that remain as the excess at the end of the distillation, Distillation Apparatus is used, found in Figure 2. Only a single substance of the mixture will be volatile, so the distillate will be a pure compound. Van der Waal forces defines the attraction of intermolecular forces between molecules. These attractions (London Dispersion Force and Dipole-Dipole Forces) will be separated. This experiment will show how molecules with higher affinity towards a mobile phase will move through the condenser more quickly than those that have a lower affinity. Polarity also plays a role, polar molecules dissolve other polar molecules and nonpolar molecules dissolve other nonpolar molecules. A hypothesis can be made about which substance will be separated through distillation based on the size and mass of the molecular compound. Ethyl Acetate is smaller in mass compared to Butyl Acetate, it can be theorize that Ethyl Acetate has a lower boiling point and should be vaporized first. 100% Ethyl Acetate should be in the first fraction, the second fraction containing a mixture of both Ethyl and Butyl Acetate, and finally, 100% of Butyl Acetate in the third fraction.

Figure 2: Distillation Apparatus

Experimental Procedures: In Part I: Procedure and Data Collection for Distillation, illustrated in Figure 1, attach a still pot to a ring stand using a clamp and place the pot just above, but not directly touching, a thermowell. The thermo-well will be the heat source. Fill the still pot, carefully, with 30mL of a 1:1 (v/v) ratio of Ethyl Acetate and Butyl Acetate. Using a clamp, attach a still head to the ring stand for added support. Add a rubber adaptor into the still head and then place a thermometer through it. The bottom of the thermometer must not be above or below the opening of the condenser. If the thermometer is not placed at the level of the opening of the condenser, then the readings will either be too high or too low of the measured boiling temperatures. The condenser needs to be attached to the still head, a clamp is used to lock the joint attachment. Next, a vacuum adapter is added to the condenser, again, a clamp is used to protect the joint between the two here. Then obtain two rubber tubes, assign both to the condenser. The other side of the front tube is require to be secured to the faucet; this allow water to flow for cooling. Then the other tubing is placed into the sink; this is so the water may escape as needed. Place a graduated cylinder below the vacuum adapter to collect the out coming liquids. And finally, add a boiling rock into the Ethyl/Butyl Acetate mixture. The thermo-well will start at 40◦C as the initial temperature to carefully heat the liquids, then increase slowly as you go. The faucets need to be turned on while the heating starts. Once boiling starts, adjust the water flow and the temperature to allow a consistent ratio of 1 drop per second

coming out of the vacuum adapter into the collecting graduated cylinder. Three graduated cylinders are needed to account for the three different fractions necessary for the experiment. A collect 10mL per fraction is only needed, any more can create an error in the results. Recording the temperatures at each 1mL of the compound collected in the graduated cylinders for each of the three fractions should be marked. Once a fraction is completed, remove it from the under the adapter and cover it with a watch glass to prevent evaporation. Part II: Analysis of Distillation Fractions by GC is accomplished in another room with separate machines. The steps to a Gas Chromatography is simple, take 5mL of a fraction in a needle provided and inject it into the column. One inject, the machine accomplishes the rest. It will read two peaks, one for Ethyl Acetate and one for Butyl Acetate. The area below the peaks should be given, once it is calculated. This will be repeated for the other two fractions. Helium is used as the mobile phase during Gas Chromatography.

Data Acquisition: Related Formulas: % Moles = Area of compound being measured x 100 Total Area Calculations: Fraction 1 =

361.6 x 100 = 81.2% Ethyl Acetate = 18.8% Butyl Acetate 361.6 + 83.81 Fraction 2 = 275.4 x 100 = 65.5% Ethyl Acetate = 34.5% Butyl Acetate 275.4 + 144.8 Fraction 3 = 70.44 x 100 = 18.0% Ethyl Acetate = 82.0% Butyl Acetate 70.44 + 320.1

Area Retention Time

Peak One 361.6 s*mV ~20 seconds

Peak Two 83.81 s*mV ~32 seconds

Identity Mol %

Ethyl Acetate 81.2%

Butyl Acetate 18.8%

Table 2: Data Table of Fraction 1 during GC.

Area Retention Time Identity Mol %

Peak One 275.4 s*mV ~21 seconds Ethyl Acetate 65.5%

Peak Two 144.8 s*mV ~34 seconds Butyl Acetate 34.5%

Table 3: Data Table of Fraction 2 during GC.

Area Retention Time Identity Mol %

Peak One 70.44 s*mV ~21 seconds Ethyl Acetate 18.0%

Table 4: Data Table of Fraction 3 during GC.

Temperature (◦C) 70 71.5 74 75 76 78 80 80 80

Volume (mL) 2.4 3 4.2 5 5.3 5.9 6.1 6.3 6.9

Table 5: Fraction 1 Results during Simple Distillation

Temperature (◦C) 82 83 84 85 86 87 88 89 90 90.5 91 93 94 94 94.5

Volume (mL) 7.9 8.2 8.8 9.3 9.7 10.3 10.9 11.1 11.7 11.9 12.5 13.1 13.5 13.9 14.2

Table 6: Fraction 2 Results during Simple Distillation

Peak Two 320.1 s*mV ~31 seconds Butyl Acetate 82.0%

Temperature (◦C) 95 96 97 98 99.5 101

Volume (mL) 15.2 15.4 16.2 16.8 17.2 17.4

Table 7: Fraction 3 Results during Simple Distillation

Graph 1: Simple Distillations of Fractions. Fraction 1 is the curve from volumes of 2.4mL to 6.9mL. Fraction 2 is the curve from volumes of 7.9mL to 14.1mL, the longest fraction. And Fraction 3 is the curve from the volumes of 15.1mL to 17.3mL. Data is found in Tables 5, 6, and 7.

Conclusion: After each fraction, it was calculated that in Fraction 1 there was 81.2% Ethyl Acetate and 18.8% Butyl Acetate. Fraction 2 was concluded to contain 65.5% Ethyl Acetate and 34.5% Butyl Acetate. And Fraction 3 had 18.0% Ethyl Acetate and 82.0% Butyl Acetate. The data, however, should had been 100% Ethyl Acetate in Faction 1 and 100% Butyl Acetate in Fraction 3, while in Fraction 2, a mixture of both. This is due to that fact that a smaller and lighter weight compound boils out faster and has a lower boiling point than a heavier one; hence, Ethyl Acetate with a molecular weight of 88.11g/mol and a boiling point of 77.0◦C, boiled out first and was found more in Fraction 1 than Butyl Acetate with a molecular weight of 116.16g/mol and a boiling point of 126.5◦C, which was found mostly in Fraction 3. It can also be concluded that Ethyl Acetate has a smaller retention time in comparison to Butyl Acetate du to Ethyl Acetate evaporating out first. This data can be found in Table 2, 3 and 4. The reason behind the experimental data was due stopping Fraction 1 and 2 too early. Each fractions’ volume amount could have reached as high as 10mL, however, during the experiment, Fraction 1 and 2 stopped around 7mL and Fraction 3 did not go passed 3.2mL because the mixture completely evaporated. However, it can also be due to the reason that the fractions where not give a watch glass to cover it after it has been completed. The compounds migthh have evaporated out of each test tube. If the experiment separated the two compounds accurately, the graph, illustrated in Graph 1, should have looked like a wide, shaped letter S. The bottom of the letter being Fraction 1. This would have concluded that Ethyl Acetate boiled out the fastest at a lower boiling point. The top of the S would represent Fraction 3. This would be a pure separation

of Butyl Acetate with a higher boiling point. The center of the wide S would represent Fraction 2. The bottom of the center would contain more Ethyl Acetate and the top half of the center would contain more Butyl Acetate.

References: Gilbert, J.C., and Martib, S.M., Experimental Organic Chemistry: A Miniscale and Microscale Approach, 4th Edition, Cengage Learning, Boston, MA, 2006. Landrie, C.L., and McQuade, L.E., Organic Chemistry: Lab Manual and Course Materials, 5th Edition, Hayden-McNeil, LLC, Plymouth, MI, 2016....