Anisole, or methoxybenzene, is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

with the formula CH₃OC₆H₅. It is a

color Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...

less liquid with a smell reminiscent of

anise Anise (; '), also called aniseed or rarely anix is a flowering plant in the family Apiaceae native to Eurasia. The flavor and aroma of its seeds have similarities with some other spices and herbs, such as star anise, fennel, licorice, and ta ...

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 Precursor or Precursors may refer to: * Precursor (religion), a forerunner, predecessor ** The Precursor, John the Baptist Science and technology * Precursor (bird), a hypothesized genus of fossil birds that was composed of fossilized parts of u ...

to other synthetic compounds. It is an

ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...

. Anisole is a standard reagent of both practical and pedagogical value. It can be prepared by the

Williamson ether synthesis The Williamson ether synthesis is an organic reaction, forming an ether from an organohalide and a deprotonated alcohol (alkoxide). This reaction was developed by Alexander Williamson in 1850. Typically it involves the reaction of an alkoxide io ...

; sodium phenoxide is reacted with a methyl halide to yield anisole.

Reactivity

Anisole undergoes

electrophilic aromatic substitution Electrophilic aromatic substitution is an organic reaction in which an atom that is attached to an aromatic system (usually hydrogen) is replaced by an electrophile. Some of the most important electrophilic aromatic substitutions are aromatic n ...

reaction at a faster speed than

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

, 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 In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

of anisole vs.

reflects the influence of the

methoxy In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula . On a benzene ring, the Hammett equation classifies a methoxy substituent at the ''para'' position a ...

group, which renders the ring more electron-rich. The methoxy group strongly affects the pi cloud of the ring as a

mesomeric Mesomeric Effect in Organic Chemistry The Mesomeric Effect The mesomeric effect (or resonance effect) in chemistry is a property of substituents or functional groups in a chemical compound. It is defined as the polarity produced in the mole ...

electron donor, more so than as an inductive electron withdrawing group despite the

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

of the

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

. Stated more quantitatively, the Hammett constant for para-substitution of anisole is -0.27. Illustrative of its

, anisole reacts with acetic anhydride to give :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 Lawesson's reagent (LR) is a chemical compound used in organic synthesis as a thiation agent. Lawesson's reagent was first made popular by Sven-Olov Lawesson, who did not, however, invent it. Lawesson's reagent was first made in 1956 during a s ...

, CH₃OC₆H₄)PS₂sub>2. Also indicating an electron-rich ring, anisole readily forms π-complexes with

metal carbonyl Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe c ...

s, e.g. Cr(η⁶-anisole)(CO)₃. The ether linkage is highly stable, but the

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ma ...

can be removed with

hydroiodic acid Hydroiodic acid (or hydriodic acid) is an aqueous solution of hydrogen iodide (HI). It is a strong acid, one that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI. Reactions Hy ...

: :CH₃OC₆H₅ + HI → HOC₆H₅ + CH₃I

Birch reduction The Birch reduction is an organic reaction that is used to convert arenes to cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent (traditionally ...

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

Preparation

Anisole is prepared by methylation of sodium phenoxide with dimethyl sulfate or methyl chloride: : 2 C₆H₅O⁻Na⁺ + (CH₃O)₂SO₂ → 2 C₆H₅OCH₃ + Na₂SO₄

Applications

Anisole is a precursor to

perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...

s, insect

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

s, and pharmaceuticals.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. For example, synthetic

anethole Anethole (also known as anise camphor) is an organic compound that is widely used as a flavoring substance. It is a derivative of phenylpropene, a type of aromatic compound that occurs widely in nature, in essential oils. It is in the class of p ...

is prepared from anisole.

Safety

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

References

External links

*
Pherobase
pheromone database entry {{Authority control Flavors Pheromones Phenol ethers Phenyl compounds