Today: Conclusion of Distillation/GC Introduction to Exp.4: Steam Distillation. IR.

Today:Conclusion of

Distillation/GC

Introduction to Exp.4: Steam Distillation. IR

Simple & Fractional Distillation Curve

GC conditions for your EA and EP Analysis:

Sample injection volume: 0.5 mL

GC column: 15 m x 0.53 mm (I.D.) PhMe-silicone stationary phase, Rtx-50 columnInitial oven temperature = 35oC

Initial time = 0.75 min

Temperature ramp = 35oC/min

Final Temperature = 70oC

Final time = 1.0 min

Column head pressure = 20 psi or more (He as Mobile Phase)

Injector Temperature = 225oC

Detector Temperature = 250oC

Detector: thermal conductivity (TCD)

RT Area Type Width Area%

(min)

.210 333265 12.35

.506 1103207 40.88

1.061 1261972 46.77

EA

EP

solventGC Chromatogram

AEA/ AEP = nEA/nEP

Area ratio = mole ratio

Task:

Determine the amount of EA as mole % EA in sample S1 and also in sample F1

Step 1: analyze the standard mixture (50:50 v/v) of EA and EP for calibration of the GC instrument

AEA = nEA x C

AEP nEP

where k = 1C

A = GC peak Area

n = molescalculate

Step 2: Calculate the mole ratio of your sample

using the correction factor obtained from the standard

for samples S1 and F1 nEA

nEP

k x AEA

AEP

=nEA

nEP

Mole ratio → mole fraction → mole %

Exp.4: Steam Distillation.

IR

Exp. 4: Isolation of a Natural Product

EugenolCH2CH CH2

HO

CH3O

CH3

H2C

CH3

CH3

CH2CH CH2

CH3C-O

CH3O

O

Caryophyllene

Eugenol Acetate

A “phenolic”.

Steam Distillation 1. What types of mixtures can be separated

by steam distillation?

2. The vapor pressure of water at 99oC is 733 torr. What is the vapor pressure of eugenol that codistills at this temperature?

3. During a steam distillation the mole ratio of two immiscible liquids is equal to the ratio of ...... ?

n1/n2 = Po1/Po

2

Steam Distillation

Dalton’s Law:P1V1 = n1RT1 and P2V2 = n2RT2

V1 = V2 and T1 = T2 n = moles,

P1V1 = n1RT1 therefore n1 = P1

P2V2 n2RT2 n2 P2

where 1= water and 2 =compound steam-distilled

Steam Distillation

n1/n2 = Po1/Po

2

(mass1/MW1) / (mass2/MW2) = Po1/Po

2

Steam distillation problem:

Benzene and water mixture boils at 69oC. The MW of benzene is 78.11. MW of water is 18.01

How many grams of water are required to steam distil 1 gram of benzene?

Use this Table 6.1 for Interpolation

Steam Distillation Which of the following boiling points

are EQUAL TO 100 degrees C, which are BELOW, and which are ABOVE ?

1. A water - eugenol mixture

2. A water- acetic acid mixture (bp. of pure acetic acid: 120 degrees C; it is miscible with water)

3. A sand-water mixture

4. A solution of NaCl in water

Direct Steam Distillation Set-up

water

150 mL water & 7g Clove buds H2O

Ice bath

Use a lab-jackBunsen burner

Separatory Funnel

ThermometerMacro-scale

Liquid-Liquid Extractionof steam distillate with methylene chloride

Which layer is methylene chloride (CH2Cl2)?

Which layer is going to contain the eugenol?

CH2Cl2

Aqu. layer

Liquid-Liquid Extraction

Plug of cotton

Anhydrous Na2SO4

“Tare” 50-mL E-flask with

one boiling chip**

Collect both MeCl layers, then boil off solvent

Infrared Spectroscopy (IR)1) What is the approximate range of wavelengths

visible to humans? And where would you find the range of IR light? How about its energy compared to visible light?

2) What are the "wavenumbers", commonly used in IR to define absorptions?

3) What type of information do we obtain from an IR

spectrum?

4) How can we identify a compound from its IR, e.g. how can we know that we obtained eugenol?

5) How will your IR tell you if your eugenol sample contains impurities?

Our next Experiment:

Exp. 10: Caffeine!