Distillations lab report PDF

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Steam and fractional distillation...

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Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus Distillations

Introduction: Simple and Fractional Distillations The purpose of this experiment is to separate a mixture of cyclohexane and toluene using fractional distillation and analyze the three resulting fractions using gas chromatography. The experiment is repeated with simple distillation to compare graphs of head temperature as a function of total distillate volume. Simple distillation is a technique used to separate volatile compounds from nonvolatile ones or to separate volatile compounds whose boiling points differ by at least 40 – 50 °C. Since the boiling points of cyclohexane and toluene differ by 30 °C, fractional distillation is expected to produce larger fractions of the pure compounds. Fraction distillation uses a steel-wool packed column to lengthen the path the vapor must take to reach the condenser. As the vapor rises, some of it condenses in the column. Through repeated cycles of condensation and revaporization, the vapor phase produced becomes increasingly richer with the more volatile component. Steam Distillation Steam distillation will be used to isolate the essential oil from cloves. The essential oil of a plant is the mixture of volatile, water-insoluble components that exhibit characteristics of the plant. Clove oil is pale yellow, has a sweet, spicy aroma, and is mainly composed of eugenol (85%). Steam distillation is used to separate and purify such volatile organic compounds that are immiscible in water. Because the compounds are immiscible, the total vapor pressure of the mixture is the sum of the vapor pressures of the pure compounds. Consequently, the boiling point for the mixture is lower than the boiling point of the most volatile component. In this case, the water-clove oil mixture will boil at a temperature less than 100 °C, the boiling point of water. Clove oil is then extracted with a separatory funnel and diethyl ether, and the ether is removed through rotary evaporation. Infrared spectroscopy is used to analyze clove oil’s components. Experimental Procedure: Simple and Fractional Distillations Obtain a 30-mL sample of the cyclohexane-toluene mixture and pour the majority into a roundbottom flask, leaving 0.5 mL for gas chromatography analysis. Set up the fractional distillation apparatus, making sure the thermometer bulb is slightly below the side arm of the still head. Use graduated cylinders to receive the three distillation fractions. Turn on the heat source to begin fractional distillation. Adjust the distillation rate to one drop every 1-2 seconds. Record the temperature and total distillate volume in 2 mL increments. Change receivers when the temperature begins to rise after the first temperature “plateau” (around 85 °C). The second plateau should occur around 104 °C. Do not let the reaction flask go dry; turn off the heat when there is 0.5 – 1 mL of liquid left in the round-bottom flask. Analyze fractions A, B, and C and the undistilled sample by gas chromatography. Calculate the areas under the peaks manually and electronically and compare. 1

Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus

Recombine the three fractions with the residual liquid in the round-bottom flask. Repeat the distillation using a simple distillation apparatus. Do not collect separate fractions; just record the head temperature as a function of total distillate volume in 2 mL increments. Steam Distillation Place a 4.0-g sample of ground cloves and 100 mL of water in a 250-mL round-bottom flask. Set up the steam distillation apparatus for use with an internal source of steam. Replace the steam inlet assembly with a glass stopped and use a 100-mL graduated cylinder as the receiver. Heat the flask strongly using a Thermowell heater and distill rapidly. Collect about 50 mL of distillate or until the distillate appears clear as opposed to cloudy. Allow the distillate to cool to room temperature. Transfer the distillate to a separatory funnel and extract the clove oil with two 15mL portions of diethyl ether, re-extracting from the aqueous layer both times. Vent frequently to release pressure. Add 15 mL of brine to the separatory funnel to reduce the amount of water dissolved in the ether. Transfer the organic layer to a 50-mL Erlenmeyer flask. Add 0.5 – 1.0 g of anhydrous calcium chloride and swirl until the organic layer is dry (completely clear). Weigh a 100-mL round-bottom flask, transfer in the organic layer, and remove the diethyl ether using a rotary evaporator. Calculate the percent recovery and obtain an infrared spectrum of the dry product.

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Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus

Table of Reagents: Compound

Mol. Wt.

Physical Properties Liquid at room temperature Boiling point: 110 – 111 °C Flash point: 4 °C Density: 0.865 g/mL at 25 °C Vapor pressure: 20 mmHg at 20 °C, 26 mmHg at 25 °C

Toluene — C6H5CH3

92.14 g

Cyclohexane — C6H12

Eugenol — C10H12O2

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Hazards: Highly flammable liquid and vapor. Causes skin irritation and serious eye damage. May cause dizziness or drowsiness. May cause damage to organs through prolonged or repeated exposure. Safety: Wear protective gloves, clothing, and eyewear. Do not breathe in vapor or fumes. Wash hands after handling. Keep away from heat, sparks, or open flames. Keep cool and in a well-ventilated area. Take precautions with static discharge. In case of fire, use carbon dioxide, dry chemical, or foam. If more than 50 mL is spilled, evacuate room and wait for toluene to evaporate and dissipate. Liquid at room temperature Boiling point: 80 – 81 °C Flash point: -18 °C Density: 0.779 g/mL at 25 °C Vapor pressure: 77 mmHg at 25 °C

Hazards: Highly flammable liquid and vapor. Causes skin irritation and serious eye damage. May cause 84.16 g dizziness or drowsiness. Safety: Wear protective gloves, clothing, and eyewear. Do not breathe in vapor or fumes. Wash hands after handling. Keep away from heat, sparks, or open flames. Keep cool and in a well-ventilated area. Take precautions with static discharge. In case of fire, use carbon dioxide, dry chemical, or foam. If more than 50 mL is spilled, evacuate room and wait for toluene to evaporate and dissipate. 164.20 g Liquid at room temperature Boiling point: 252 – 254 °C Flash point: 127 °C

Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus Density: 1.067 g/mL at 25 °C Solubility: Immiscible with water Hazards: Causes skin and eye irritation. May cause an allergic skin reaction. Safety: Wear protective gloves, clothing, and eyewear. Do not breathe in vapor or fumes. Wash hands after handling. In case of allergic reaction, get medical attention. Liquid at room temperature Boiling point: 34.6 °C Flash point: -45 °C Density: 0.706 g/mL at 25 °C

Diethyl ether — C4H10O 74.12 g

Hazards: Extremely flammable liquid and vapor. Harmful if swallowed. May cause drowsiness or dizziness. May cause organ damage through repeated exposure. Safety: Wear protective gloves, clothing, and eyewear. Do not breathe in dust or fumes. Wash hands after handling. Keep away from heat, sparks, or open flames. Keep cool and in a well-ventilated area. Take precautions with static discharge. In case of fire, use carbon dioxide, dry chemical, or foam. If more than 50 mL is spilled, evacuate room and wait for ether to evaporate and dissipate.

Molecular structures, weights, and physical properties from Sigma-Aldrich. https://www.sigmaaldrich.com (accessed June 11, 2019). Molecular formulas, physical properties, and safety from Alfa Aesar by Thermo Fischer Scientific. https://www.alfa.com (accessed June 11, 2019).

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Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus

Results & Observations: Figure 1. Fractional Distillation Plot of Temperature vs. Volume

Fraction A was collected at the 15.3 mL mark and contained 15.3 mL. Fraction B was collected at the 17.6 mL mark and contained 2.3 mL. Fraction C was collected at the 26.2 mL mark and contained 8.6 mL.

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Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus

Figure 2. Fractional Distillation Plot of Temperature vs. Volume

Table 1. Gas Chromatography Settings Gas Chromatograph: #6 Column: B Volume: 2.5 µL Polarity: (-) Current: 100 mA Column Temperature: 101 °C Detector Temperature: 150 °C Injector Temperature: 130 °C

Table 2. Gas Chromatography Analyses Mixture Percent Cyclohexane Undistilled Y 48.3 Fraction A 85.2 Fraction B 46.4 Fraction C 2.9 6

Percent Toluene 51.7 14.8 53.6 97.3

Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus

Figure 3. Comparison of Manual & Electronic Methods

See attached gas chromatography plots for results and calculations. Table 3. Steam Distillation of Eugenol Initial Mass of Clove

Final Mass of Clove Oil

Percent Recovery

3.96 g

0.59 g

14.9%

Observations:  Ground clove is a reddish-brown powder that smells sweet and spicy.  When dissolved in water, it forms a brown solution with insoluble particles in a mass at the bottom of the flask.  The distillate is cloudy-white. The first drop occurred at 100 °C.  The final clove oil product was clear with a spicy scent. See attached for infrared spectrum. 7

Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus

Conclusions: Fractional distillation is a far more effective technique for separating a mixture of cyclohexane and toluene than simple distillation. As indicated by the fractional distillation plot, there are two clear plateau phases separated by a fast rise in temperature occurring over only a few milliliters of distillate. The first plateau phase occurs from 73 – 80 °C and represents Fraction A, the majority cyclohexane fraction. Fraction B contains a mixture of cyclohexane and toluene and occurs between 80 and 102 °C. This fraction is very small, containing only 2.3 mL. The second plateau phase occurs from 102 – 103 °C and contains Fraction C, the majority toluene fraction. In the simple distillation plot, it is impossible to distinguish the two plateau phases or the rapid rise in temperature that is expected in-between. The plot appears nearly linear due to the consistent slow rise in temperature throughout the procedure. If fractions were separated during this simple distillation, the constant temperature increase would not only have hindered the ability to distinguish between the fractions but would also have resulted in greater impurities in fractions A and C, ideally pure cyclohexane and toluene respectively. According to gas chromatography analysis, undistilled sample Y contained 48.3% cyclohexane and 51.7% toluene. This is close to the expected values of 50% cyclohexane and 50% toluene. Fraction A contained 85.2% cyclohexane and 14.8% toluene. Ideally this fraction should have contained pure cyclohexane, but some error is to be expected given the subjective decision on when to change receivers. Fraction B was 2.3 mL and contained 46.4% cyclohexane and 53.6% toluene. As expected, this fraction was very small and contained a mixture of the two compounds at a ratio similar to the undistilled sample. Fraction C contained 2.9% cyclohexane and 97.1% toluene. This is extremely pure as is ideal. As seen in Figure 3, the manual “triangulation” method for calculating peak areas yielded results similar to those obtained with the electronic integrator. The difference in area calculated between the methods ranged from 0 to 27 mV*s, a relatively small margin of error. The manual method was likely this effective because the peaks were more or less symmetrical. In summary, the manual method is effective for calculating areas when electronic methods are unavailable. The infrared spectrum obtained from the final clove oil product closely resembles the spectrum of pure eugenol, confirming that the product is very pure. There is a broad, strong peak at 3516.48 that corresponds with the O-H group of eugenol. An alkene C=C peak is seen at 1637.84 with the corresponding =C-H at 3075.94. The saturated C-H peak is below 3000 at 2936.99. Within the fingerprint region, it is difficult to attribute specific peaks to functional groups given how many and how close the peaks are. Nevertheless, some peaks could correspond to the benzene ring (1450 – 1600) and the C-O of the ether and alcohol functional groups (1050 – 1300). The only significant difference between the published spectra of eugenol and the experimental one of the final product is the presence of a small peak at 1764.65. This may 8

Experiment #3 Date: 6/19/2019

Name: Kiran Raja TA: William Neuhaus

indicate the presence of an ester or another carbonyl compound. However, the peak may also be an artefact. Answers to Assigned Questions: 9 1 mole =0.178moles Cyclohexane: 15 g × 84.16 g 0.178 =0.77 0.178+ 0.054

Toluene:

5g×

1 mole =0.054 moles 92.14 g

0. 054 =0. 23 0.178+ 0.054 13 0.2 × 406=270.67 torr 0.2+0.1 0. 1 ×222=74 torr Ethanol: 0.2+ 0.1 Total: 344.67 torr Methanol:

8 a. Aniline is immiscible or nearly immiscible in water. b. Aniline and water will co-distill at approximately 100 °C or less. c. The normal boiling point of aniline is 183 – 184 °C. Citation: Alfa Aesar by Thermo Fischer Scientific. https://www.alfa.com (accessed June 17, 2019). Alfa Aesar ID Number A14443. Why is a steam distillation rather than a simple distillation performed in the isolation of clove oil from cloves? Eugenol, the main component of clove oil, has a boiling point range of 252 – 254 °C. Performing a simple distillation to isolate eugenol would require substantial time and energy to reach the boiling point temperature. A steam distillation allows for purification of volatile organic compounds that are immiscible in water. Because eugenol is one such immiscible compound, the total vapor pressure of a eugenol-water mixture is the sum of the vapor pressures of the pure compounds. Consequently, the boiling point for the mixture is lower than the boiling point of the most volatile component. In this case, the water-clove oil mixture will boil at a temperature less than 100 °C, the boiling point of water.

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