Anisole

Reactivity

Anisole undergoes electrophilic aromatic substitution reaction at a faster speed than 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. Stated more quantitatively, the Hammett constant for para-substitution of anisole is –0.27.

Illustrative of its nucleophilicity, anisole reacts with acetic anhydride to give : Unlike most acetophenones, but reflecting the influence of the methoxy group, methoxyacetophenone undergoes a second acetylation. Many related reactions have been demonstrated. For example, phosphorus pentasulfide () converts anisole to Lawesson's reagent, .

Also indicating an electron-rich ring, anisole readily forms π-complexes with metal carbonyls, e.g. .

The ether linkage is highly stable, but the methyl group can be removed with strong acids, such as hydroiodic acid or boron trichloride: :

Birch reduction of anisole gives 1-methoxycyclohexa-1,4-diene.

Synthesis

Anisole was first synthesized in 1841 by Auguste Cahours by barium anisate decarboxylation while heating p-anisic acid he made earlier from the anise essence with barium oxide:

It can be prepared by the Williamson ether synthesis from sodium phenoxide and dimethyl sulfate or methyl chloride: :

Applications

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

Safety

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

Popular culture

In the board game Scrabble, the word "anisole" is the 39th-most-likely word (out of over 25,000 possibilities) for a "bingo"/"bonus", i.e. the deployment of all seven letters in one's own hand simultaneously.

References

References

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2. {{March6th
3. I. Thomsen. (1984). "Thiation with 2,4-Bis(4-Methoxyphenyl)-1,3,2,4-Dithiadiphosphetane 2,4-Disulfide: ''N''-Methylthiopyrrolidone". Organic Syntheses.
4. E. Peter Kündig. (2004). "Synthesis of Transition Metal ''η''⁶-Arene Complexes". Topics Organomet Chem..
5. A. J. Birch and K. B. Chamberlain. (1977). "Tricarbonyl[(2,3,4,5-''η'')-2,4-Cyclohexadien-1-one]Iron and Tricarbonyl[(1,2,3,4,5-''η'')-2-Methoxy-2,4-Cyclohexadien-1-yl]Iron(1+) Hexafluorophosphate(1−) from Anisole". Organic Syntheses.
6. Wisniak, Jaime. (2013-10-01). "Auguste André Thomas Cahours". Educación Química.
7. Crochard (París). (1841). "Annales de chimie et de physique". Chez Crochard.
8. G. S. Hiers and F. D. Hager. (1929). "Anisole".
9. Helmut Fiege. "Phenol Derivatives".
10. [http://www.seas.upenn.edu/~nanofab/chemicals/MSDS_Solvent_Anisole.pdf MSDS] {{webarchive. link. (July 1, 2010)
11. "Fun with analytics: Probabilities and Scrabble".