Clove Oil Experiment - Lab Report PDF

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Chem 303

Isolation and Identification of the Principal Constituent of Clove Oil Purpose: The purpose of this experiment is to isolate clove oil from freshly ground cloves. The principal constituent will be separated from the clove oil by a chemically active extraction as this constituent is soluble in aqueous alkali. The structure of this component, which has a molecular formula of C10H12O2, will be elucidated with the aid of IR and 1 H NMR spectroscopy. Procedure: The procedure of this lab can be found in Organic Puzzle Book pages 31-33. Observations and Data: 1. Characterize your IR spectrum and the authentic IR spectrum of the principal constituent, A, of clove oil in tabular form in the usual manner. Identify as many peaks in the spectra as possible. Peak (cm-1)

Intensity

Broad or Sharp

Eugenol Peaks (cm-1)

Peak Types

3077.03

67.544

Sharp

3077

=C-H

3004.04

67.694

Sharp

3004

=C-H

2975.49

67.510

Sharp

2976

C-H

2938.13

67.545

Sharp

2939

C-H

2843.17

68.888

Sharp

2843

C-H

1636.21

70.535

Sharp

1638

C=C

1615.39

71.187

Sharp

1613

C=C

1514.27

60.073

Sharp

1514

Aromatic C=C

Plateau Temperature: 2. Summarize the 1 H NMR spectrum of A, taken in CDCl 3. Assign the peaks to specific protons in the molecule. Peak (ppm)

Area

Splitting Pattern

Functional Group

a

5.48

1

s

OH

b

5.06

1

t

Aromatic Hydrogen

c

5.06

1

t

Aromatic

Chem 303

Hydrogen d

6.85

1

d

Aromatic Hydrogen

e

3.33

2

d

-CH2

f

5.06

2

q

Vinylic 2H

g

5.95

1

ddt

Vinylic H

h

3.88

3

s

Methyl Group

3. Carefully analyze the complex multiplet centered at δ 5.96 ppm in the 1 H NMR spectrum of A, taken in CDCl3. You should be able to “extract” three different coupling constants from an analysis of this multiplet. Coupling Constants (Hz) 7 10 17 4. And, this is where the second NMR spectrum of Compound A, taken in C6D6, comes into play. Unfortunately, the 2H multiplet at δ 4.98-5.05 ppm is still not first order. However, the three

Chem 303

protons between δ 6.4 and 7.05 ppm are now nicely resolved. Please assign these peaks to the specific protons in A. And, explain the observed splitting patterns and make coupling constant assignments. Ha couples with Hc (8 Hz) and engages in long range coupling with the benzene ring ( 1.7 Hz). Hc only has long range coupling of aromatic rings (1.9 Hz).

5. What structure do you propose for the principal constituent, A, of clove oil? Do your IR and H NMR spectral data corroborate each other? If not, explain why. I propose the principal constituent of clove oil is eugenol. The IR Spectra confirms the presence of the OH peak, Aromatic Hydrogen Peaks, and C=C peaks. The 1 H NMR spectral data also corroborate the functional groups (See table for more details).

1

6. Calculate the percentage of A obtained, based on the mass of ground cloves used. % Yield of Clove Oil =

51.184𝑔−50.795𝑔 0.398 𝑔 = 5.00 𝑔 5.00𝑔

× 100= 7.96%

Discussion: 1. The methylene chloride layer remaining after the aqueous alkaline extractions, which was discarded, still contained some residual A. However, the major component of this methylene chloride layer was the secondary constituent, B, of clove oil. Compound B has a molecular formula of C12H14O3. The IR spectrum of B is quite similar to the IR spectrum of A, except that the broad band centered at about 3500 cm-1 is absent, while an intense band at 1765 cm-1 is now present. Additionally, the 1 H NMR spectrum of B, taken in CDCl3, is similar to the NMR spectrum of A. The 1H singlet at ~ δ 5.5 ppm in the NMR spectrum of A is absent in the spectrum of B, while the spectrum of B displays a new 3H singlet at δ 2.31 ppm, which is absent in the spectrum of A. Propose a structure for the secondary constituent, B, of clove oil. Explain how you arrived at this proposed structure.

Chem 303

There is no OH peak in the IR spectrum for this new compound since there is no broad peak at 3500 cm-1 is absent. The sharp peak at 1765 cm-1 indicates the existence of a C=O group. Hence the most obvious option is to include an ester functional group in the compound. The presence of acetate is supported by the disappearance of 1H singlet at ~ δ 5.5 ppm and the appearance of the 3H singlet at 2.31 ppm. The molecular formula also backs up the proposed structure as well. 2. Carefully explain the basis of the chemically active extraction of the principal constituent, A, of clove oil. Explain why A is soluble in aqueous alkali, while B is not. The extraction of the principal constituent can be conducted by adding NaOH to the clove oil mixture in DCM solution. The acidic phenol group on the principal constituent will be deprotonated by NaOH to form an anion and enter the aqueous layer. B does not possess a phenol group that can be ionized and dissolved in aqueous alkali and therefore cannot be deprotonated. Conclusions: The principal constituent of clove oil is eugenol as evidenced by IR and NMR spectroscopy. The percent yield of clove oil is 7.96%....