Isolation and Characterization of Eugenol from Cloves

Objectives:

1. To isolate eugenol and neutral product from cloves by using steam distillation

2. To characterize eugenol and natural product by gas chromatography spectroscopy (GC-MS) and IR spectroscopy

Introduction:

Eugenol, C₁₀H₁₂O₂ is a one of the compound of phenylpropanoid family. It is a pale yellow oily compound that extracted from essential oil especially from cloves and bay leaf.

Figure 1 Molecular structure of eugenol

In this experiment, the eugenol(essential oil) and neutral product are isolated from cloves by using the technique of co-distillation with water, this process is also known as steam distillation. Both eugenol and neutral product are separated from water by acid-base extraction. The characterization of eugenol and neutral product are performed by using IR spectroscopy and gas chromatography and mass spectroscopy (GC-MS).

Apparatus:

Glassware and retort stands for steam distillation, distillation flask, mortar and pestle, round bottom flask, separatory funnel, Erlenmeyer flask, heating mantle

Materials:

Cloves, tert-butyl methyl ether (BME), 6M HCl, 3% NaOH, saturated NaCl, pH paper, magnesium sulphate anhydrous

Instruments:

IR spectroscopy, gas chromatography-mass spectrometer

Procedures:

 

 

 

 

 

 

 

 

 

 

 

Results and calculations:

Table 1: Weight of neutral product and eugenol

Weight of round bottom flask I	98.2705g
Weight of round bottom flask I + neutral compound	98.2862g
Weight of neutral product	0.0157g
Weight of round bottom flask II	61.2657g
Weight of round bottom flask II + eugenol	61.5005g
Weight of eugenol	0.2348g

Weight of cloves = 10.0000g

Percentage yield of neutral product (terpene) = 0.0157g / 10g x 100%

= 0.157%

Percentage yield of eugenol = 0.2348g / 10g x 100%

= 2.348%

Table 2: Significant stretches of standard and extracted eugenol and their respective values

Sources	Expected values (from table)	Extracted eugenol	Standard eugenol	Journal (Rahimi, Ashnagar, & Nikoei, 2012)
Significant stretches	Wavenumber, v
O-H stretch	3200-3600cm-1	3516.0cm-1	3429.0cm-1	3514.3cm-1
C=C stretch	1620-1680cm-1	1637cm-1	1638.0cm-1	1637.6cm-1
Aromatic C=C stretch	1400-1600cm-1	1612.0cm-1, 1513.0cm-1, 1464.0cm-1	1604.0cm-1, 1514.0cm-1, 1465.0cm-1	1608.0cm-1, 1513.8cm-1, 1459.5cm-1
C-O stretch	1100-1300cm-1	1268.0cm-1, 1235.0cm-1	1267.0cm-1, 1234.0cm-1	1268.8cm-1, 1234.2cm-1

Table 3: Significant stretch of terpene and the respective value

Significant stretches	Wavenumber, v
C=C stretch	1638cm-1

Table 4: Retention time at each significant peak in GC-MS spectrum

Source	Standard eugenol	Isolated eugenol
Retention time (minute)	4.579	4.581

Discussion:

The amount of eugenol and neutral product obtained experimentally are 0.2348g and 0.0157g respectively. The composition contributed by eugenol is 2.348% whereas neutral product (usually is terpene) gives 0.157% of yield.

When the clove exposed to steam, the volatile terpene evaporated and condensed in the distillate. In the steam distillation process, both eugenol and terpene were obtained in the distillate. In order to separate the both compounds from others, tert­-butyl methyl ether (BME) was used in the separation. The aqueous layer was appears at upper layer while organic layer at lower layer since BME is less dense than water. The organic layer only contains eugenol and neutral product after the extraction with BME.

In order to isolate eugenol from the extract, sodium hydroxide was introduced to convert eugenol to form a sodium salt as shown in the following diagram.

Diagram 2 Sodium salt of eugenol

The sodium salt dissolved in the aqueous layer and hence eugenol was separated from the terpene in organic layer. The organic layer was partitioned and BME was removed by using rota-vapor and hence terpene was extracted.

For aqueous layer, concentrated hydrochloric acid was introduced to protonate sodium salt to form eugenol. A cloudy solution was formed during the addition of hydrochloric acid. This is because the eugenol formed from the acidification did not dissolve in aqueous layer. Finally, eugenol was extracted by using BME and the organic solvent was removed.

Magnesium sulphate anhydrous, a drying agent was used to remove all the water in the organic layer. Water in the organic compound could reduce its purity and hence the analytical characterization will be affected especially in IR spectroscopy and gas chromatography and mass spectroscopy.

From the IR spectrum of standard eugenol, the wavenumber shows: 3516cm^-1 (O-H stretch), 1637cm^-1 (C=C stretch), 1612cm^-1, 1513cm^-1, 1465cm^-1 (aromatic C=C stretch), 1267cm^-1, 1234cm^-1 (C-O stretch). Compared to extracted eugenol, the spectrum showed: 3429cm^-1(O-H stretch), 1638cm^-1 (C=C stretch), 1604cm^-1, 1514cm^-1, and 1464cm^-1 (aromatic C=C stretch), 1268cm^-1, 1235cm^-1 (C-O stretch).

Based on the GC-MS spectrum, standard eugenol shows the significant peak at retention time of 4.579 minute whereas isolated eugenol shows the important peak at retention time of 4.581 minute. Both isolated and pure eugenol shows the same retention time which indicates eugenol can be extracted from cloves.

Precaution steps:

1. Do not use separatory funnel point to anybody when releasing the vapour.

 

 

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