Anisole

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Anisole
Anisol.svg Anisole-3D-balls.png
Identifiers
CAS number 100-66-3 YesY
ChemSpider 7238 YesY
UNII B3W693GAZH YesY
KEGG C01403 YesY
ChEBI CHEBI:16579 YesY
ChEMBL CHEMBL278024 YesY
Jmol-3D images Image 1
Image 2
Properties
Molecular formula 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
Hazards
LD50 3700 mg/kg (rat, oral)
Except where noted otherwise, 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.

Reactivity[edit]

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[edit]

Anisole is prepared by the Williamson ether synthesis, reacting sodium phenoxide with methyl bromide and related methylating reagents:[1]

C6H5ONa+ + CH3Br → CH3OC6H5 + NaBr

Applications[edit]

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

Safety[edit]

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

See also[edit]

References[edit]

  1. ^ G. S. Hiers and F. D. Hager (1941), Anisole, Org. Synth. ; Coll. Vol. 1: 58 
  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. ^ a b MSDS

External links[edit]