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 column
Initial 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)
GC Chromatogram
solvent
RT
EA
EP
Area Type
Width
Area%
(min)
.210
333265
12.35
.506 1103207
40.88
1.061 1261972
46.77
Area ratio = mole ratio
AEA/ AEP = nEA/nEP
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
AEP
=
nEA
x C
nEP
calculate
where k =
1
C
A = GC peak Area
n = moles
Step 2:
Calculate the mole ratio of your sample
using the correction factor obtained from the
standard
nEA
nEP
k x
for samples S1 and F1
AEA
AEP
=
nEA
nEP
Mole ratio → mole fraction → mole %
Exp.4:
Steam Distillation.
IR
Exp. 4:
Isolation of a Natural Product
CH3O
Eugenol
HO
CH2CH
CH2
A “phenolic”.
CH3
CH3
Caryophyllene
CH3
H2C
CH3O
Eugenol Acetate
CH3C-O
O
CH2CH
CH2
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/Po2
Steam Distillation
Dalton’s Law:
P1V1 = n1RT1 and
V1 = V2 and T1 = T2
P1V1
P2V2
=
P2V2 = n2RT2
n = moles,
n1RT1 therefore n1 = P1
n2RT2
n2
P2
where 1= water and 2 =compound steam-distilled
Steam Distillation
n1/n2 = Po1/Po2
(mass1/MW1) / (mass2/MW2) = Po1/Po2
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
Macro-scale
Thermometer
Separatory
Funnel
water
150 mL water &
7g Clove buds
Bunsen burner
H2O
Ice
bath
Use a lab-jack
Liquid-Liquid Extraction
of steam distillate with methylene chloride
Which layer is methylene chloride (CH2Cl2)?
Which layer is going to contain the eugenol?
Aqu. layer
CH2Cl2
Liquid-Liquid Extraction
Anhydrous Na2SO4
Plug of cotton
“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!