Question

Introduction:

This week you will be learning another important technique in the organic chemistry laboratory – distillation. Distillation uses the difference in boiling point of two miscible liquids and thus separates compounds by exploiting different volatilities. While often used in the chemical laboratory, the process itself is a physical separation that uses phase changes (gas / liquid) to effect either complete or partial separation. In the simplest form distillation consists of 2 phase changes, evaporation followed by one condensation step (simple distillation), whereas fractional distillation repeats the process of evaporation followed by condensation inside a distillation column. Besides the physical separation, distillation also provides you with a measure of purity as you will be able to constantly monitor the boiling point of the distillate and compare it to literature values. To corroborate your results of this week’s experiment, you will additionally perform gas chromatography of the distillates that you obtain. Gas chromatography allows for the analytical separation of compounds based on their boiling point and will serve in your experiment as a basis for determining the purity of the distillate. You will be given a mixture of 2 alcohols and will perform either a simple or a fractional distillation on it. You will then analyze your distillates using gas chromatography, determine the percent composition and thus the success of your distillation.

Questions for the experiment and the analysis:

1) Using the provided GC sample runs including integrations of each of the alcohol mixtures BEFORE the distillation, determine the percent of each of the alcohols in the sample

2) Obtain and tabulate the results of the other five procedures carried by the class

3) For all six procedures, compare the boiling ranges throughout the distillation, as well as the percent composition of the first and last collected fraction

4) Using this data, determine which distillations were successful in separating the two alcohols and which ones were unsuccessful. Make sure to compare this with the theory of distillation and the performance you should expect for simple vs fractional distillation

5) Based on those results, what factor seemingly determines whether a good separation is possible through distillation?

Lab Results:

Impure Methanol:Propanol

Peak 1: Retention Time (min)= 1.290, Area= 19.56, %Area= 7.25

Peak 2: Retention Time (min)= 2.140, Area= 250.19, %Area=92.75

Impure Methanol:Ethanol

Peak 1: Retention Time (min)= 1.265, Area= -4.83, %Area= 14.00

Peak 2: Retention Time (min)= 1.405, Area= -29.67, %Area= 86.00

Impure Methanol:Butanol

Peak 1: Retention Time (min)= 1.305, Area= 30.79, %Area= 3.41

Peak 2: Retention Time (min)= 3.690, Area= 872.07, %Area= 96.59

5 Procedures Carried by the Class Results:

Student 1:

Methanol:Ethanol- first test tube (simple distillation)

Peak 1: Retention Time (min)= 0.860, Area= 0.89, %Area= 4.42

Peak 2: Retention Time (min)= 1.035, Area= 16.92, %Area= 84.16

Peak 3: Retention Time (min)= 1.110, Area= 2.29, %Area= 11.41

Methanol:Ethanol- last test tube (simple distillation)

Peak 1: Retention Time (min)= 1.195, Area= 198.76, %Area= 100.00

Student 2:

Methanol:Ethanol- first test tube (simple distillation)

Peak 1: Retention Time (min)= 1.755, Area= 12.87, %Area= 100.00

Methanol:Ethanol- last test tube (simple distillation)

Peak 1: Retention Time (min)= 1.615, Area= 44.11, %Area= 100.00

Student 3:

Methanol:Ethanol- first test tube (fractional distillation)

Peak 1: Retention Time (min)= 1.555, Area= 11.11, %Area= 98.84

Peak 2: Retention Time (min)= 1.690, Area= 0.13, %Area= 1.16

Methanol:Ethanol- last test tube (fractional distillation)

Peak 1: Retention Time (min)= 1.496, Area= -0.19, %Area= -1.95

Peak 2: Retention Time (min)= 1.585, Area= 10.07, %Area= 101.95

Student 4:

Methanol:Ethanol- first test tube (fractional distillation)

Peak 1: Retention Time (min)= 1.465, Area= 67.70, %Area= 100.00

Methanol:Ethanol- last test tube (fractional distillation)

Peak 1: Retention Time (min)= 1.710, Area= 196.05, %Area= 100.00

Student 5:

Methanol:Propanol- first test tube (simple distillation)

Peak 1: Retention Time (min)= 1.840, Area= 193.42, %Area= 93.47

Peak 2: Retention Time (min)= 2.425, Area= 13.51, %Area= 6.53

Methanol:Propanol- last test tube (simple distillation)

Peak 1: Retention Time (min)= 2.520, Area= 830.06, %Area= 100.00

Student 6: (My Experiment)

Methanol:Propanol- first test tube (fractional distillation)

Peak 1: Retention Time (min)= 1.640, Area= 105.78, %Area= 94.71

Peak 2: Retention Time (min)= 2.205, Area= 5.90, %Area= 5.29

Methanol:Propanol- last test tube (fractional distillation)

Peak 1: Retention Time (min)= 2.410, Area= 790.25, %Area= 100.00

Student 7:

Methanol:Propanol- first test tube (fractional distillation)

Peak 1: Retention Time (min)= 1.685, Area= 42.94, %Area= 100.00

Methanol:Propanol- last test tube (fractional distillation)

(no peak)

Student 8:

Methanol:Butanol- first test tube (simple distillation)

(no peak)

Methanol:Butanol- last test tube (simple distillation)

(no peak)

Student 9:

Methanol:Butanol- first test tube (simple distillation)

Peak 1: Retention Time (min)= 1.090, Area= 272.21, %Area= 84.34

Peak 2: Retention Time (min)= 2.420, Area= 50.53, %Area= 15.66

Methanol:Butanol- last test tube (simple distillation)

Peak 1: Retention Time (min)= 3.210, Area= 1421.66, %Area= 100.00

Student 10:

Methanol:Butanol- first test tube (fractional distillation)

Peak 1: Retention Time (min)= 1.090, Area= 1.92, %Area= 0.20

Peak 2: Retention Time (min)= 2.070, Area= 2.23, %Area= 0.24

Peak 3: Retention Time (min)= 3.010, Area= 932.02, %Area= 99.56

Methanol:Butanol- last test tube (fractional distillation)

Peak 1: Retention Time (min)= 0.906, Area= 0.25, %Area= 0.13

Peak 2: Retention Time (min)= 1.040, Area= 144.64, %Area= 76.40

Peak 3: Retention Time (min)= 2.435, Area= 44.44, %Area= 23.47

My Boiling Points for Methanol:Propanol (fractional distillation)

1/2 mL of Distillate	test tube 1	tube 2	tube 3	tube 4	tube 5	tube 6	tube 7
0.5	69	74	76	79	81	84	90
1	73	75	77	79	82	85	91
1.5	75	75	78	79	82	86	92
2	74	75	78	80	83	87	92
2.5	74	75	78	81	84	88	93
3	75	75	78.5	81	84	90	74