ANETHOLE

Anethole (Synonym Anise camphor, Monasirup)

1-Methoxy-4-(1-propenyl)-benzene
Formula:	C10H12O
CAS#:	104-46-1
MW:	148.2

1-methoxy-4-propenylbenzene
4-propenylanisole
1-methoxy-4-[(E)-prop-1-enyl]benzene
1-methoxy-4-[(E)-prop-1-enyl]benzol
1-méthoxy-4-[(E)-prop-1-enyl]benzène
1-メトキシ-4-[(E)-プロプ-1-エニル]ベンゼン

Melting Point: 23 ºC
Boiling Point: 234-237 ºC

Density: 0.9875 g/mL
Refractive Index: 1.5610

It has a monohydric phenolic ether function.

Occurrence It is the chief constituent of anise (anise fruit, aniseed) i.e., the dried ripe fruits of Pimpinella anisum Linn' (Family: Umbelliferae); star anise (star anise fruit, Chinese anise i.e., the dried ripe fruits of Illicium verum Hoop (Family: Magnoliaceae); and fennel (fennel fruits finnocchio), i.e., the dried ripe fruits of Foeniculum vulgare Mill (Family: Apiaceae). It is also found in Ocimum basilicum L. (Family: Lamiaceae)-Sweet Basil, Garden Basil; Pinus elliottii Engelm. (Family: Abiataceae)-Slash Pine; Sassafras albidum (Nutt.) Nees (Family: Lauraceae)-sassafras; and Syzygium aromaticum (L.) Merr & Perry (Family: Myrtaceae)-cloves, clavos.

Isolation It may be isolated from the volatile oils by first subjecting the oil to fractionation and then cooling the corresponding fraction to a very low temperature and recrystallization. However, it may also be obtained directly from the anethole-rich oils, such as: oil of anise, oil of fennel by simply chilling it to – 30°C in a deep freezer. Commercially, anethole may be synthesized in its purest form from anisole as shown below:

Anisole on reacting with propionaldehyde in the presence of HCl and H₃PO₄ yields an intermediate anisole-p-(1-chloropropane) which finally with pyridine yields anethole.

Characteristic Features It exists in two isomeric forms namely: trans-and cis-isomer, having physical parameters as stated below:

It is a white crystalline substance with an intense sweet odour. It possesses a characteristic taste similar to anise fruit. It is practically soluble in most organic solvents but insoluble in water.

Formation of ‘Photoanethole’ (or p, p′-dimethoxystilbene) Anethole on exposure to air (oxygen), light or heat undergoes structural modifications to yield photoanethole which is a viscid yellow coloured mass having a disagreeable taste and odour with a poor solubility in solvents. Perhaps the conversion of anethole to photoanethole lakes place via the formation of anisaldehyde as given below:

Identification

1. Anethole undergoes oxidation with K₂Cr₂O₇ in two steps; first step-yields anisaldehyde (paramethoxy benzaldehyde), and second step-gives rise to para-methoxy benzoic acid (mp 184°C) as depicted below:

2. It gets condensed with maleic anhydride to yield a condensation product having mp 310°C as shown below:

3. It gives rise to the formation of nitroso derivative having mp 126°C.

Uses

1. It is used as a flavouring agent in perfumery particularly for soap and dentifrices.

2. It is also employed as a pharmaceutical and (flavour).

3. It finds its application as an imbedding material in microscopy.

4. It is employed as a flavouring agent in alcholic, non-aleoholic beverages and confectionaries.

5. It is used as a sensitizer in bleaching colours in colour photography.

Anethole, C10H12O, a major constituent of the oil of anise, has the 1H NMR spectrum shown.


1H NMR




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13C NMR

OXYGEN ATTACHED CARBON IS UPFIELD AT 158.7

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MS


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IR




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http://www.google.com/patents/EP0203386B1

• Example 2. Anethole, (4-Propenylanisol), is extracted from Fennel, or Foeniculum Vulgare Mill. 1 kg of grated Fennel is extracted with 3 l of 95% ethanol at room temperature for 24 hrs. Ethanol is recovered by distillation under reduced pressure from the ethanol extract and a residue containing crude anethole is dissolved in 1 l of distilled water. This aqueous soluton is distilled under reduced pressure whereby Fennel oil is distilled over with steam. Crude Fennel oil is separated from water and extracted with an equal volume of diethyl ether. The ether extract is distilled under reduced pressure thereby recovering the diethyl ether and a residue of Fennel oil respectively. Yield of this crude Fennel oil is about 5.5%.
• [0015]
  The resulting Fennel oil is fractionated with reflux on an oil bath. The fraction collected at a distilling temperature from 229-237°C is Anethol.
  

  overall yield:

  3.3%
  Anethole has the following chemical structure:
  

  

  Anethole has a light yellow color.

  specific gravity:

  at 25/25°C 0.983 - 0.987

  refractive index at 25°:

  1.588 - 1.561

  REFERENCES

  Seeman, J.I., Grassian, V.H., and Bernstein, E.R. 1988. J. Am. Chem. Soc. 110:8542-8543.

  Lange, G., and Schultze, W. 1992. Org. Mass Spectrom. 27:481-488.

  Vella, A.J. 1992. Org. Mass Spectrom. 27:145-150.

  Baxendale, I.R., Lee, A.-L., and Ley, S.V. 2002. A polymer-supported iridium catalyst for the stereoselective isomerisation of double bonds. Syn. Lett. 3:516-518.

  Polkanov, M.A., Shapiro, I.O., Chernoplekova, V.A., and Shatenshtein, A.I. 1988. J. Org. Chem. USSR (Engl. Transl.). 24:1123-1127. The Journal of Organic Chemistry, 50, p. 1797, 1985 DOI: 10.1021/jo00211a002 Tetrahedron, 24, p. 2183, 1968

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