Anisole

Anisole
IUPAC name	methoxybenzene
Other names	anisole and phenoxymethane
Identifiers
CAS number	100-66-3 Y
SMILES	COc1ccccc1
Properties
Molecular formula	C7H8O
Molar mass	108.14 g/mol
Density	0.995 g/cm³
Melting point	−37 °C
Boiling point	154 °C
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Anisole is the organic compound with the formula CH₃OC₆H₅. This colorless liquid has a smell reminiscent of anise seed. It is used as a precursor to other organic compounds. Substituted derivatives are also called anisoles.

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, moreso than the inductive effect of the electronegative oxygen.

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

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

Unlike most aromatic compounds and reflecting its high reactivity, the methoxyacetophenone undergoes a second acylation:

CH₃OC₆H₄C(O)CH₃ + (CH₃CO)₂O → CH₃OC₆H₃(C(O)CH₃)₂ + CH₃CO₂H

Many related reactions have been demonstrated. For example, P₄S₁₀ converts anisole to Lawesson's reagent, [(CH₃O₆H₄)PS₂]₂.

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

CH₃OC₆H₅ + HI → HOC₆H₄C(O)CH₃ + CH₃I

Preparation

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

2 PhO⁻Na⁺ + CH₃Br → CH₃OC₆H₅ + NaBr

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 LD50 of 3700 mg/kg in rats.^[3]

See also

• Anethole
• Bromoanisole
• Butylated hydroxyanisole
• Ether
• Ethyl phenyl ether
• Phenol
• 2,4,6-Trichloroanisole (cork taint)

References

1. ^ G. S. Hiers and F. D. Hager (1941), "Anisole", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0058 ; Coll. Vol. 1: 58 
2. ^ Helmut Fiege, Heinz-Werner Voges, Toshikazu Hamamoto, Sumio Umemura, Tadao Iwata, Hisaya Miki6, 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. ^ MSDS.[1]

External links

• International Chemical Safety Card 1014
• Pherobase pheromone database entry