Anisole

Anisole
Names
Preferred IUPAC name
Anisole
Systematic IUPAC name
Methoxybenzene
Other names
Methyl Phenyl ether
Phenoxymethane
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.002.615
KEGG
UNII
Properties
C7H8O
Molar mass 108.14 g·mol−1
Appearance Colorless liquid
Density 0.995 g/cm3
Melting point −37 °C (−35 °F; 236 K)
Boiling point 154 °C (309 °F; 427 K)
Solubility Insoluble
-72.79·10−6 cm3/mol
Hazards
NFPA 704
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g., diesel fuel Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
2
2
0
Lethal dose or concentration (LD, LC):
3700 mg/kg (rat, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Anisole, or methoxybenzene, is an organic compound with the formula CH3OC6H5. It is a colorless liquid with a smell reminiscent of anise seed, and in fact many of its derivatives are found in natural and artificial fragrances. The compound is mainly made synthetically and is a precursor to other synthetic compounds. It is an ether.

It can be prepared by Williamson synthesis : reacting sodium phenoxide ion with methylhalide to yield methoxy benzene.

Reactivity

Anisole undergoes electrophilic aromatic substitution reaction more quickly than does benzene, which in turn reacts more quickly than nitrobenzene. The methoxy group is an ortho/para directing group, which means that electrophilic substitution preferentially occurs at these three sites. The enhanced nucleophilicity of anisole vs benzene reflects the influence of the methoxy group, which renders the ring more electron-rich. The methoxy group strongly affects the pi cloud of the ring as a mesomeric electron donor, more so than as an inductive electron withdrawing group despite the electronegativity of the oxygen.

Illustrative of its nucleophilicity, anisole reacts with acetic anhydride to give 4-methoxyacetophenone:

CH3OC6H5 + (CH3CO)2O → CH3OC6H4C(O)CH3 + CH3CO2H

Unlike most acetophenones, but reflecting the influence of the methoxy group, methoxyacetophenone undergoes a second acetylation. Many related reactions have been demonstrated. For example, P4S10 converts anisole to Lawesson's reagent, [(CH3OC6H4)PS2]2.

The ether linkage is highly stable, but the methyl group can be removed with hydroiodic acid:

CH3OC6H5 + HI → HOC6H5 + CH3I

Preparation

Anisole is prepared by methylation of sodium phenoxide with dimethyl sulfate or methyl chloride:[1][2]

2 C6H5O−Na+ + (CH3O)2SO2 → 2 C6H5OCH3 + Na2SO4

Applications

Anisole is a precursor to perfumes, insect pheromones, and pharmaceuticals.[2] For example, synthetic anethole is prepared from anisole.

Safety

Anisole is relatively nontoxic with an LD50 of 3700 mg/kg in rats.[3] Its main hazard is its flammability.[3]

See also

References

  1. ↑ G. S. Hiers and F. D. Hager (1941). "Anisole". Org. Synth.; Coll. Vol., 1, p. 58
  2. 1 2 Helmut Fiege, Heinz-Werner Voges, Toshikazu Hamamoto, Sumio Umemura, Tadao Iwata, Hisaya Miki, Yasuhiro Fujita, Hans-Josef Buysch, Dorothea Garbe, Wilfried Paulus “Phenol Derivatives“ in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_313
  3. 1 2 MSDS Archived July 1, 2010, at the Wayback Machine.
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